All that aside, this post is related to Joe Carroll’s last topic–reduced gravity research facilities. His talk reminded me that I needed to dig-up and finish this blog post I had started back in May about the importance of such reduced gravity research facilities, and a clever approach I had seen to providing them.

Reduced Gravity Effects on the Human Body
I first made this point almost five years ago, but it bears repeating: while we have a lot of data on human health at 1g and at 0g, we have almost no data in the middle. I say almost, because we did have a dozen people live on the moon for at least 24 hours each…but that’s pretty much the only data we have on reduced gravity health effects, which is far too little to draw any really useful conclusions.

Most readers of this blog know that the data from microgravity impacts on the human body don’t look too promising–even with lots of exercise, there are apparently biophysical mechanisms that can have large negative health impacts (osteoporosis, neurological and pulmonary issues, etc) that begin to show themselves very quickly. However, as I pointed out in that earlier post, we have no idea which of the curves below really represents human health impacts of reduced gravity:

Does just a little bit of gravity go a long way (my personal guess I explain in the other post)? Or do you need almost full earth gravity? Or is there actually some gravity level less than 1g that’s actually better than earth gravity? While natural selection for humans has obviously been focused on a 1g environment, that doesn’t mean that humans are so hyperoptimized to 1g that nothing else will do. It’s unfortunately possible, but right now we don’t know. Without getting some “center points”, any guess at the shape of the response curve is just that–a guess.

Why This Matters
The reason why this knowledge void matters is that it greatly impacts the future expanse of humanity into space, as well as near-term human exploration. For instance, we don’t know if someone who goes to live on the Moon or Mars can ever really come back to earth, or if they have kids, if their kids can return.

If however it turns out that lunar gravity is already enough to counteract the worst of the effects of microgravity, it might be that the best way to do initial lunar human exploration is something like a One-Way To Stay (for a while) approach. If you knew that you could send someone for long durations while still being able to bring them back later if needed, it would open up some big possibilities. The return portion of a human lunar mission is one of the big performance drivers that make human missions so much more expensive than robotic ones. Even if you couldn’t close the life-support loop, just not having to return the initial explorers right away could allow you really enhance robotic exploration of the Moon by having people there on the spot to help troubleshoot, fix, upgrade, iterate, etc on your robotic systems. I know a lot of people think we can just send robots and have them make a turn-key base. It’s possible, but I expect you’re going to break a lot of robots along the way, and you could avoid that by having people in the loop. But its ethically hard to do a mission like that before you have some data on what long-duration exposure to 1/6g is going to do to your explorers.

Returning to the Joe’s talk, he suggested looking at .06g as well as lunar and martian gravity, as a possible minimal gravity level that people could intuitively adapt to without lots of training. If travelers can get by without large negative health hazards by .06g worth of gravity, that would really simplify the concept of providing artificial gravity for long-duration deep-space trips (like to Mars or NEOs). If there’s a “knee in the curve” above which you can avoid the worst of microgravity effects, that can make it a lot easier to provide artificial gravity for trips like that. If you have to provide a full 1g, and can’t go with high RPMs (which Joe suggested that the terrestrial centrifuge data might be suspect due to the presence of a 1g downward gravity vector), that implies very large structures, which become a much bigger engineering challenge.

xGRF
The question becomes, what’s the best way to get this data? Most of these effects take timescales on the order of hours, days, or weeks to express themselves. And there’s no way on earth to adequately simulate hypogravity. The only real way of testing this, short of going there and finding out the hard way, is to build some sort of orbital research facility. The ISS was originally going to have a Centrifuge Accommodations Module, but that project got defunded, and the hardware is no longer flightworthy from what I hear. I had suggested the idea of doing a “CAM in a Can” before, but even that would be limited to studying small animals–there’s no way you could fit a human in there. To get the data quickly, you really want some sort of artificial gravity facility that is human-sized. In his presentation, Joe Carroll talked about building a large rotating space station with facilities on different lever arms from the CG of the facility. While this is interesting, and would allow you to have your gravity decoupled from your spin rate, I think that Kirk Sorensen’s xGRF “Variable Gravity Research Facility” concept makes more near-term sense (Joe and I disagree on this point BTW).

I’m not sure if Kirk reads this blog very much anymore (he’s pretty busy at his new job as Chief Nuclear Technologist at Teledyne Brown), but I have to toot his horn a bit. While not all of his ideas are ones I’m sold on, he’s had more than his fair share of clever ideas. The idea behind xGRF is very simple. You have a small facility–something on the scale of a Sundancer or Nautilus module from Bigelow, and you attach it via a long tether to a large counterweight (such as the upper stage that delivered the module to orbit in the first place). In LEO the gravity gradient can be used to force such a system to adapt an orientation with the long axis pointing through the center of the earth. In such a situation, the CG will be somewhere between the two end pieces, and the module will be going slightly slower than the orbital velocity of other components at its altitude, and the counterweight will be going slightly faster. This provides a tiny bit of settling force on each end (acting like a tiny bit of gravity with a vector pointed outward from the center of the system).

Ok, you may be thinking, that’s nice. But where do you get the “Variable” Gravity from? That’s where Kirk’s idea gets really clever.

Basically, something in a gravity gradient orientation is still actually spinning–it just completes one complete rotation per orbit around the earth…What happens if you take a spinning object like this, and decrease it’s moment of inertia by, oh say winching in the tether? By conservation of angular momentum, the object has to start spinning faster!

You can winch the habitat and the counterweight together until you reach the desired level of artificial gravity. Depending on the design details, you can pick any gravity level you want between say microgravity and 1g. How do you dock, say to transfer crews or deliver supplies? Well, it turns out you can despin the system by just reeling out the tether:

Pretty clever. By doing this, not only can you pick any gravity level you want, but you can also do your rendezvous and docking in a simple, non-spinning environment, you can eliminate the need for having rotating and nonrotating parts of the station, or of long elevators or connecting tunnels. I really like this concept, because the system ends up being pretty simple, with everything being able to be launched on a single EELV flight. You don’t have to assemble a huge space facility and then spin it up. This can be a small project that might actually get built. I think the big station Joe might have more capabilities, but I’m worried that detractors would paint it as a second ISS, and it would never get funded. Something on this scale though is within the realm of feasibility.

Flagship Technology Demonstrators, Expansion Options, Future Uses, and other Parting Shots
One particularly interesting way to get something like this funded (and what I was originally writing this blog post back in May as a response to) is as a replacement for the “Inflatable Technology” Flagship Technology Demonstrator. Back in Galveston late last spring, NASA rolled out several proposed FTD missions to flesh out plans suggested in Obama’s FY11 budget proposal. One of the missions was to build an inflatable module and attach it to ISS. To be honest, this seemed a little duplicative–it looked for all intents and purposes as though NASA was going to spend $500M-1B duplicating what Bigelow was doing on his own dime. I think a much better way of both flight demonstrating inflatables while killing multiple birds with one stone would be to build something like xGRF as a Flagship Technology Demonstrator. Leverage either a Bigelow Sundancer module or compete it out and have ILC Dover also bid on it. For the same amount of money, you get a much more useful lab, that doesn’t endanger the ISS, and which allows you to do reduced gravity research that compliments ISS’s microgravity focus.

As Joe pointed out, even after the initial experiments (say at lunar gravity first, then Martian, then at the .06g level), a facility like this would have lots of follow-on utility. You can answer initial questions relatively quickly–ie even a few months at each level would tell you a lot compared to what we know right now, but getting longer-duration data could be very useful for future space settlement efforts. I’ll have to dig up my notes on all the reasons, but there’s a lot of long-term potential for a station like this.

Which means you might also want to upgrade it down the road. If you overbuild the tether, and the docking facilities, you could probably attach additional modules to a station like this pretty readily. To add to the counterweight, you could say have facilities on the original upper stage that could allow it to be outfitted as a depot…but that’s getting a little too crazy for now.

But I think the time for something like this is now. FTDs are getting money, even if it’s greatly reduced from what Obama wanted. The budget for exploration technology development, including flagship missions is currently authorized at over $1.1B over the next three years. At that rate, you could fund most of the work on both the depot approach that was proposed by the joint industry/NASA group I participated in last year, as well as xGRF, and still have money left over for starting another FTD like say an aerobraking or aerocapture one. Even if funding gets further reduced in appropriations, there’s enough money to pursue something like xGRF and depots in parallel.

I think this is an idea whose time has come.

As far as implementing this idea, the technology isn’t the hard part. Technologically, this is something that could’ve been done in the 70s. Modern technology and modern launch services make it a whole lot easier and more feasible, but the technology isn’t the key obstacle. Money is and always has been the biggest obstacle. But I think I have an idea, and it’s just crazy enough that I want to share it.

Any business plan whose first step is “first we convince a billionaire to give us lots of money” usually deserves to be laughed off the stage. But this isn’t a business plan competition entry, or some pitch before VCs that I’m demanding to be taken seriously, so I’m going to suggest just that. Even with a wealthy philantrocapitalist, I think you’d still want a concept that both gives you a reasonable chance of making the money back if things go well as well as minimizing your losses if it doesn’t work out.

Anyhow, this is a bit of a long-shot, and definitely not fully-baked, but here’s what I have so far. The business case revolves around a few core concepts:

• A privately developed simple lander and an ITAR approved method for launching it on both US and domestic launchers.
• Using barter with various space agencies with domestic medium-lift vehicles to provide both the startup launches and the sustaining launches
• Making revenue off of selling remaining space to corporations, research institutions, and smaller countries that are interested in lunar experiments, but lack indigenous launch capabilities
• Possibly offsetting initial lander development by selling rover delivery services to NASA or other large space agencies.

Some of these sound a bit crazy, so why don’t I explain them in turn.

Private Landers
The key technology piece in the project is obviously the lander. As discussed before, I’m thinking of something in the 10-20klb IMLEO range, with a payload in the 4-6klb range. The propellant combination for the lander doesn’t hugely matter. It could use storables like Martijn likes, it could use space storables like LOX/Methane or LOX/Propane. Heck, it could even use LOX/LH2. While the state of the VTVL industry isn’t quite mature enough where you could just order one of these custom and have it delivered to your launch pad 6 months ARO, a lander in these capability ranges isn’t a huge stretch for the commercial space industry, especially if they can partner wisely with some of the more traditional space companies or work with NASA via Space Acts. DC-X was actually a much bigger, probably more complicated system, and was done by a traditional aerospace company for around $100M in current dollars. A bare-bones lander, developed leveraging the emerging capabilities in the entrepreneurial community could probably be fielded for less than that. Possibly in the $50M range. You don’t need to push too hard on mass fractions or engine performance (you need to push a bit, but it isn’t as weight critical as some of the Apollo LM systems), and the technology is a lot more mature than it was in the 60s.

An important part of this process is not just developing the lander, but also working from the start with ITAR to make sure a process is in place that will allow you to launch on as many international launch vehicles as is feasible. This may not be fun, but is probably doable with appropriate precautions.

International Horse-Trading
Most space agencies prefer to spend money within their own borders, and interact with other agencies on a barter basis as much as possible. While this can sometimes lead to suboptimal solutions, it might just work in this situation. On the launch side, the barter would go something like this–the private entity would provide a lander, all lander ops, and physical launch integration work, and the space agency (NASA, ESA, RSA, JAXA, ISRO, or CNSA) would provide the lifter and upper stage for the mission. The launching country would get a certain share of the lander’s cargo space for their own experiments, a certain portion would be reserved for consumables and spare parts, and the remainder would be owned by the private entity to resell to other countries without launch capabilities (say a 40/40/20 split). In addition to transportation of the space hardware, the launching country would also get a share of the astronaut’s time on the surface. So basically you’re providing them with transportation and manned experimentation on the lunar surface in exchange for them providing a launch done by their own people. If one of the countries is willing to take some additional risks, they could even “buy” one of the two initial astronaut slots, in exchange say for a commitment to a certain higher share of the logistics launches per year. In exchange they’d get both the prestige of having one of the initial lunar crew, as well as a higher share in the available time. Over time, as the risk decreases, the initial crew could also be expanded (once again on barter terms that would have the agency in question shouldering a larger share of the required launches).

It should be mentioned how crazy of a bargain this really is for them in comparison to the typical lunar mission approach. Look at Constellation. It will be a lot more capable, but ultimately, somewhere around $10B/yr (and about $150B up-front), you get 4-person years/yr (2x 4-man crew rotations) and about 75klb of cargo (2x 17mT landings) on the moon once you have a base setup. Calling it a 60/40 split on costs (for manned vs cargo flights), that comes out to $1.5B per person-year, and about $53k/lb on the lunar surface–ignoring development costs. With a program like this, say you gave a country 1/4 of a man-year per launch, and about 1800lb, at a cost to them of call it a $200M launcher plus extra upper stage for the transfer. Splitting that $200M the same way (60/40), that gives you $480M per person year, and about $45k/lb on the surface. You don’t save a huge amount per pound of cargo on the surface, but your cost per person hour is about 1/4 as much (which is once again not too surprising–you’re not rotating crews, and not having to carry enough propellant to get them home–which takes about 4x as much mass per mission compared to a one-way manned landing). And you don’t have to spend tens of billions up-front, and you can buy your lunar program “by-the-slice”. Paying for an extra launch every year (and some lunar systems costs) is well within the budget capabilities of many of these agencies. While they might not be willing to take the risk of flying their own astronauts, or of “owning” the program, they are a lot more likely to be interested in a program like this, where someone else is shouldering the key risks, and they’re just getting a cheap deal. Even if they have their own lunar ambitions down the road, using a service like this would allow them to drastically reduce their technological risk moving forward, and might allow them to get a lot more benefit out of their investment when they eventually get that capability themselves.

“Sovereign Customers”
One of the key markets Bigelow is looking at for his inflatable space habitats is providing smaller countries with a way to participate in space for much cheaper than trying to do everything in-house themselves. By lowering the cost to participate, it makes it a lot more feasible for smaller countries, and even some corporations or research institutions to participate. This may be a country like South Korea wanting to send a rover that can get maintained by the astronauts over time. It may be a country wanting to do its own sample return mission–with the ability to have a human on the ground helping to presort/preprocess samples to maximize the bang for the buck. It could be a company like Catepillar that wants to get involved in lunar surface systems for future exploration programs sending a bunch of bearing concepts to test exposed to the lunar environment. It could be some small startup that has a crazy idea for lunar dust mitigation that it wants to try selling to future government programs, but needs testing and debugging first. There are many possibilities. The key here is that since the launch is already paid for, the private entity running all this can price the payloads however makes the most sense. You do need to cover lander costs, ground-ops costs, and the time of the scientists, but it might be possible to offer these slots at a price that is lower than they could buy commercially to try and stimulate demand, or if there is enough demand already you could price it high enough to make a decent profit. If there’s enough demand, you might even be able to justify paying for an additional “purely commercial” flight or two per year. You would want to save up some of the money to cover contingencies–like if something breaks down and you have to fly an emergency resupply flight on short notice, or if you decide for one reason or another to throw-in-the-towel after a few years, you can send enough propellant to get the settlers home. But depending on the interest level, this could easily be a business that has revenues in the low hundreds of millions per year.

Minimizing the Initial Risk
One additional market for the lander, and one that could allow the initial investment to be recovered a lot faster, would be to see if you could sell it to one of the space agencies for landing a rover or some other scientific package. The key here is that the lander is getting developed, on the philantrocapitalist’s own dime regardless of if he can presell any lander slots. This makes it easier to sell it as a commercially available service instead of a government funded development program. Using a light Atlas vehicle for instance (maybe with one or two strapons) you could probably short-load the vehicle enough to put a couple hundred pounds of useable payload onto the lunar surface. For a bundled price of say $200-250M for the launcher and lander, it would still be a steal transportation-wise for your customer, but could possibly pay off the initial costs of the project in one shot, even before the initial landings. The good news is that while its great if you can presell the landers for other applications, it isn’t the end of the world if you can’t.

One other way of minimizing the downside may be to see if you can prearrange the initial several launches. If you can line up enough international partners, it may be possible to get the initial setup done without having to actually buy any of the launches yourself. You’d still have to pay for the landers, but this way your total capital at risk for the startup is only the cost of 3-4 landers.

Anyhow, comments? thoughts? attempts to send nice young men in their clean white jackets to cart a certain space blogger away?

To me one of the more interesting points is found at the top of page 11.  There were several misleading statements made by several people today about the relative safety of Ares-I compared to commercial crew vehicles.  As Brett put it (my emphasis added):

Second, some have claimed that NASA’s Exploration Systems Architecture Study (ESAS) shows that the current exploration vehicles are safer than commercial crew vehicles. In actuality, commercial crew vehicles were never even analyzed in the ESAS report – the ESAS report only looked at vehicles large enough to carry Orion, such as Ares I and variants of the triple-core Delta IV Heavy, and did not examine the smaller, simple, single-core vehicles, such as Atlas V Medium and Falcon 9 Medium that are sufficiently sized for commercial crew missions.  Moreover, even if ESAS had compared exploration vehicles to commercial crew-sized vehicles, the comparisons would be “apples vs. oranges,” because of the dramatically different tasks of these two types of vehicles.

When Jeff Hanley talks about how the Great Oz and supercomputers at NASA show that Ares-I is 3x safer than commercial launch vehicles, I wonder if he’s ever going to release their analyses for actually commercial crew vehicles, or if he’s being accidentally or intentionally dishonest. Because so far we haven’t been shown any data about the safety of actual commercial crew launchers. So far we have lots of data shown for the risks of using existing or modified commercial launch vehicles for launching a massive spacecraft designed to go to and return from the moon, including significant plane change maneuvers to allow anytime returns (ie Orion). It’s interesting to note that over half of the mass on Orion is the oversized launch escape system needed to get away from an SRB you can’t shutoff, and enough propellant for about 1500m/s of maneuvering to reach orbit and then to do in-space ops. That’s above and beyond the RCS propellant on the CM itself.

Most of the stuff that make Orion so massive are flat-out completely unnecessary for an earth-to-LEO crew capsule. You don’t need those kinds of delta-V capabilities. You don’t need as roomy of facilities, since by definition the flight times should be a lot shorter. Etc. There’s a reason why almost all of the proposed commercial crew systems are able to utilize single-stick launchers like Atlas V or Falcon 9–for an actual earth-to-LEO capsule you really don’t need anything bigger.

This realization that earth to LEO capsules can be much smaller than Orion leads to at least two important corollaries that I can think of:

1. Smaller capsules mean higher structural margins.  One of the existing vehicles most often suggested for commercial crew, Atlas V, was designed for the worst-case loading environment of any of its configurations (in this case I believe that would be the Atlas V 551 or 552).  The Atlas V 552 sees much higher max-Q’s than the 401/402 do, and has a much heavier payload on top, which exerts much larger structural loads on the Centaur stage than are seen in the 401/402 configuration.  While the Centaur structures may not meet the 1.4 magic number NASA likes in some of the bigger configurations, as I understand it, it actually exceeds that number in the 401/402 config most likely used for commercial applications.  The Falcon 9 was designed from the start to meet NASA structural margin specs.
2. No need for strapons.  Only one of the commercial crew ideas I’ve seen so far used a vehicle with strapons for crew launch (Dreamchaser).  This alone should make a huge difference in launcher reliability, since there are less things that can go wrong, less staging events, etc.  Most of the commercial launcher ideas they mentioned in ESAS assumed multi-core configurations.

There’s also the possiblity on the Atlas-V of using a dual-engine Centaur configuration to allow for some upper stage engine-out capability, or running the RL-10 at a derated performance level (not sure if that’s something it can do automatically, or if you’d have to make modifications–if you have to modify it it probably isn’t worth it).  With the much lower max-Q, and the ability to shut off the booster engine in case of an abort, I have a hard time believing that Ares-I is really that much more reliable than an actual commercial crew capsule launched on a commercial launch vehicle that has dozens of flights under its belt.

Food for thought.

The mission uses the following tricks to make things work:

• Dual Engine Centaur for this mission is stretched by 50% and includes an “Extended Mission Kit” to allow for it to function for the ~5 days necessary for the mission (normal DEC dry mass is ~5400lb, and the EMK is ~1750lb and includes stuff like extra hydrazine bottles, more batteries, deep space navigation upgrades to avionics, sunshields, etc)
• Command module does a powered lunar swingby to go to L2, thus cutting down on overall dV requirements (~750m/s total required, 335m/s per leg), thus allowing for a much smaller CSM (possibly with the service module integrated into the command module).
• The Stretched Centaur and the Lander break into lunar orbit and descend to the surface instead of continuing to L2.  I’m not positive if this allows you to land anywhere on the lunar surface or not (this is one of the few big questions for this mission mode).  This avoids the extra dV requirements you normally get for stopping everything at L2 first.
• Upper stage performs part of the landing burn (between LOI and the descent burn it provides about 1950m/s out of the total 3050m/s needed for LOI and landing).
• RS-68A Upgraded Delta-IVH. This upgrade is already in engine testing and is badly needed by the DoD, so there’s a good chance this will work out.  Expected payload capacity I’ve heard is 27mT for the system.
• Instead of carrying a second stretched Centaur as a payload on one of the flights, the Atlas V 552 uses the stretched Centaur as its upper stage.  In order to tank up the LH2, it carries an LH2 drop tank between the lander and the command module.  It gets transfered right after reaching orbit, and gets dumped shortly before TLI.

Here are the major components of the system:

• Command Module: This module is based on the Apollo outer mold line, but only carries two people, and enough life support consumables for the mission.  I budgetted 11,000lb dry and 3250lb of propellant for the capsule (not including RCS propellants).  I assumed hypergols for the stage, with a crappy 314s Isp.  The Apollo CM wet mass was 12.8klb, and the SM weighed 54klb wet, 13.5klb dry.  However, most of the SM mass was due to the CSM performing the LOI burn for the Apollo Stack.  About half of the dry mass of the CSM was the huge main engine, and a good chunk of the remaining mass was electrical equipment and the huge tanks for the 40klb of propellant.  With modern materials, electronics, a smaller crew, solar panels instead of fuel cells, and the much lower propulsive requirements for the Command Module in this architecture, I think 11klb is actually pretty conservative for such a system.  For another comparison the latest CEV numbers I’ve heard (which are pretty far out of date) were ~18klb for a four person capsule.
• Stretched Centaur Lunar Transfer/Crasher Stage:  As mentioned above, this is a dual engine centaur using two RL10A-4-2 engines, but with a 50% barrel stretch to the tanks.  The tanks are actually less than 40% of the dry mass of a centaur stage, but you also need more helium for pressurization of the larger stage…assuming that the 50% greater propellant load requires a 50% higher dry mass should be a conservative estimate.  The idea of a stretched Centaur shouldn’t be too crazy when you realize how many iterations General Dynamics, Martin Marietta, and Lockheed Martin have done on the Centaur just in the past 20 years (including 5m diameter Centaurs for use on Titan IV among other things).  The 1750lb for the extended mission kit is also based on numbers from previous papers LM/ULA has published about converting their stages over for longer-duration missions.  Total dry mass I assumed was 9850lb.  Note that the Atlas V 552 performance numbers also include 5400lb worth of Centaur burnout weight, so you only have to provide ~4450lb worth of “payload” for the Stretched Centaur.  Also note, that if you tank the stretched Centaur up all the way for launch, it should probably increase the payload capacity of the Atlas V 552 a little compared to a normal Centaur, but for purposes of this analysis we’re assuming only the nominal payload of a normal Atlas V 552, to be conservative.
• Single Stage Lunar Lander/Ascender: This stage takes the crew the rest of the way to the lunar surface after the Centaur has provided the first part of the descent burn, and then provides the ascent burn, and the burn to take the crew to the L2 staging point to rendezvous with the Command Module.  I budgetted 1100m/s for its portion of the descent burn, 100m/s to allow for a 90s hover to find the best landing spot, 2650m/s for the lunar surface to L2 burn, and about 50m/s more for contingencies.  This is probably the most aggressive part of the mission.  For this vehicle, I’m assuming a piston-pump-fed LOX/CH4 stage, based off of the piston pump and LOX/Methane engine work XCOR has done  (possibly combined with stuff that we at Masten have done that they haven’t like gimbals, throttling, etc).  The piston pump requires very low net peak suction head, which allows for very low pressure tanks, that can be made of  the LOX/Cryo-compatible Nonburnite composites that XCOR has been devleoping.  XCOR developed the piston pump and Nonburnite composites explicity for making propellant tanks out of shapes that aren’t typical for propellant tanks (in their cases to make the CG numbers work, they wanted to do LOX-filled “wet wings”).  Using this technology, instead of heavy pressure fed tanks and heavy helium tanks, you have lightweight composite tanks that can actually form part of the load-bearing structure of the vehicle.  As I understand it, based on my recollection of their public statements, the piston pumps they’re looking at using scale to about enough flow for a 2500lbf engine in a single pump.  By combining them with the 7500lbf engine XCOR developed (with a nozzle extension of course), you have significantly more thrust than you need for landing.  More importantly, you can possibly make the three pumps operate in a redundant fashion, so the loss of one pump can be tolerated at any point in the mission, and the loss of a second pump can be tolerated through most of the mission.  If done right, the pumps could be “armored” as XCOR calls it, but placed in such a way that they have removable manways between them and the main compartment that would allow for shirtsleeve troubleshooting/repair (the pump compartments would need to be done in a manner that if something went horribly wrong, that any debris/blast would be directed away from the crew cabin…but I can imagine a few ways that could be done).  All told, I’m assuming a 4350lb dry weight, a 9000lb propellant weight, 500lb worth of hardware to be left on the moon, and a 360s Isp.  The LM ascent stage was 4200lb, but held only 65% of the propellant mass, and only about half the propellant volume of this lander, and didn’t have to do landings, and didn’t have to support the crew for as long (about 3 days vs. the target 9 days to give you a week on the surface and 2 days in transity to L2).  But as mentioned above, it used pressure fed tanks, with the mass of a helium blowdown system, had to provide significant RCS capabilities since the stage did not have a gimballed main engine, was using crappy 60s era electronics and electrical systems, and had tanks that were entirely non structural, and also didn’t have access to modern materials like lithium-aluminum or modern composites.  However, the 13,850lb total mass for the lander actually compares pretty well with the 13,510lb currently assumed for the pressure-fed, hypergol-fueld Altair Ascent stage (from this document), which carries 4 crew for the same mission duration.
• Pre-Depot LOX Tank: This ~2.2klb Tank holds ~57.1klb of LOX for the Stretched Centaur.  It includes a docking port (possibly using LIDS technology?), a sunshield, and a Centuar-derived LOX tank.  It gets launched as the sole payload for the Delta-IVH, using up all but about 200lb of its capacity.  But since it is so dense, it might be able to get away with using a shorter (and lighter weight) fairing than is typical for Delta-IVH if that wouldn’t require lots of expensive aero analysis.  This tank, if launched with the LOX pre-chilled can hang out for over a month waiting for the Atlas V 552 launch.
• LH2 Drop Tank: This ~62.5 m^3 tank weighs about 2000lb (with another 2000lb budgetted for connecting structures between the various parts of the launch stack).  It would be housed between the Lander and the Command Module on the Atlas V 552 launch.  It would possibly use 5m tankage derived from the Delta-IV US.  After reaching orbit, the LH2 from this tank would be transfered (using propulsive settling) into the Stretched Centaur.  After the Command Module docks with the Pre-Depot LOX tank, and has transferred all the propellants from that (and discarded the pre-depot LOX tank), the CM and empty LH2 drop tank would separate from the stack, the drop tank would be discarded, and the CM would reattach to the lander much like was done on the Apollo Missions.

Now, this mission model isn’t perfect.  It uses most of the capabilities of the two launchers without a huge amount of margin (except in the fact that the Atlas V 552 with stretched Centaur probably has some margin built in that isn’t being explicitly called out).  And I’m not a fan of launching the crew on an EELV with 5 solid strapons.  It would be a lot easier if you assumed the development of something like the Common Upper Stage that ULA has been talking about recently.  With that, you would have tons more margin (since a CUS would add nearly 7mT of capacity to the DIVH, and probably at least 5mT to the Atlas V 552–possibly enough to go with less or no strapons on the crew launcher).  But it demonstrates that a 2-launch EELV mission using almost no modifications to existing launch vehicles (beyond the Centaur mods) is within feasibility.

The system also has several good things going for it.  First off, it can deliver lunar crew to the surface without a depot.  It doesn’t need Autonomous Rendezvous and Docking (since the rendezvous and docking can be piloted), or tankers to be developed.  It doesn’t need HLVs or 10m fairings (everything can fit within a stock Atlas V fairing).  It doesn’t need really long term LH2 storage in orbit.  It only requires two launches for the mission, and doesn’t put anywhere near as much launch timing constraints as the ESAS architecture does.  It can provide for cargo missions (~19klb delivered mass to the surface assuming that 2klb of the lander stage is in the form of a removable crew cabin, which just happens to be enough to land a Bigelow Module).

And most importantly, if depots do come into existence, it can immediately take advantage of them.  With just an LEO depot, you can both cut down on the number of EELV launches to just one (and use lower-cost systems like Falcon 9′s, Zenits, Ariane-Vs, Soyuzes, future commercial RLVs, etc to launch the remaining propellant).  Also by getting rid of the huge LH2 drop tank, you simplify the stack, remove about 15klb worth of hardware from the Atlas stack , dropping it to the point where it can possibly be launched by a 502 launch instead of a 552 launch (since the stretched Centaur provides almost as much propellant as a Phase 1 Atlas, which was supposed to boost the LEO capacity of the single-stick Atlas to almost 30klb).  Or you could use that saved mass to beef up the lander and/or command module for more capable missions.

If you have both a LEO and an L1 or L2 depot, the Centaur can top itself up again that depot, and provide a much larger chunk of the descent burn to the lander stack.  With enough propellant left over to return to LLO then to L1/L2 after separating from the lander, allowing the Stretched Centaur to be reused multiple times.  With such a system you could actually soft-land bigger payloads than the Altair cargo lander…and you’d have the capability of making the lander and transfer stage fully reusable.  The transfer stage, since it wouldn’t see atmospheric flight, reentry, lunar dust, or even particularly bad thermal environments should actually be reusable for several flights–the RL10 is after all rated for 200 relights.  The lander may be tougher, but by the time you have an L1/L2 depot, you’ve probably had enough time (and enough surface infrastructure built up) that you can work that out to.

Ok, so maybe it’s not so bad of an idea after all.

The presentation was done by a company called Honeybee Robotics, that has been doing space robotics systems for over 20 years.  I found out about them through a joint project they had been doing with one of our new neighbors at the Mojave Spaceport, Firestar Engineering.  They had worked together on using the mixed nitrous monoprop that Firestar is developing as a gas generator for a lunar pneumatic excavation idea (which is discussed in this presentation, and also in this paper on using it for a Mars or Lunar sample return mission).  I’ve been interested in the concept of pneumatic excavation ever since I read an article titled “Foundation Slab for Lunar Base Construction” that was presented at the fourth ASCE conference on Engineering, Construction, and Operations in Space back in 1994.  The concept seemed to show a way of producing very large enclosed subselenian areas for relatively small initial investments in hardware and materials.  Anyhow, my curiosity on the topic led me to do some searches to see if I could dig up any more information about their Lunar Pneumatic Excavator concept, and that led me to the presentation I wanted to write about in this post.

I’d strongly suggest reading the whole thing, but here are my notes on the paper:

• Lunar regolith is highly compacted, abrasive, high surface friction, and sticks together very strongly.  All of these things drive up excavation forces.
• Most terrestrial excavation equipment uses the weight of the vehicle and the friction forces in its wheels/tracks to react against the excavation forces.
• Lower lunar gravity means that for typical lunar excavators, you might actually need several times heavier equipment to do the same job.
• Methods that lower the excavation force required can greatly reduce the mass requirement for the excavation equipment.
• Percussive/Vibratory excavation systems can lower the force and excavator mass requirements dramatically for such situations (up to a 10x mass reduction).
• Pneumatic excavation can be done using a coaxial tube setup, where the inner tube blows low-pressure gas at the regolith, and the slightly longer outer tube provides a return path for the gas vent.  Gas doing the turn from the inner tube to the outer annulus imparts momentum into the regolith, and then entrains the regolith particles in the gas forcing it up the outer tube (see illustration below)

• In an experiment performed on a vomit comet, they showed that a lunar pneumatic excavator system operating at 7psia, could give a regolith mass excavated to gas expended ratio of over 3000:1 in a 1/6g environment (ie each gram of gas could move over 3kg of regolith)
• Such excavation techniques can also be used for sample return or prospecting missions, using relatively simple hardware with almost no moving parts.

They didn’t go into it much, but if you could store the gas as a liquid (either inert, or as rocket propellant), and then vaporize or combust it before shooting it down the nozzle, you could excavate a pretty sizable amount of regolith using a pretty small volume of liquid.   That means that a tank about the same size as the propellant tanks we’re using on XA-0.2 (36in spherical tanks) could hold enough liquid CO2 to excavate enough regolith to bury a Bigelow Nautilus module.  Of course, to move the regolith back, you’d need another tank that big.  Call that about 700lb of CO2 and about 100lb of tankage.  Not bad if those numbers are accurate.

Anyhow, read the presentation and that other article, and post your thoughts in comments.

1. Overemphasis on Unmanned Cargo: I’ve previously discussed on this blog what I think is one of the key deficiencies of the current COTS approach–the focus on cargo delivery to ISS while ignoring the crew delivery issue.  The problem with a focus on just cargo delivery to ISS is that a cargo delivery capability doesn’t really open up many other markets.  Sure, there may be a few flights here and there for DragonLab, but the reality is that without a passenger delivery capability, there just isn’t much need for such capabilities, outside of NASA’s ISS needs.  Bigelow, for instance isn’t going to be providing much demand for cargo flights if he can’t get people to his station.  The ability to safely fly people to orbit, and to be able to deliver them to/retreive them from space stations is a lot more useful.  Not only would NASA be a potential customer, but also Bigelow, and even free-flights.  And once you start getting more demand for people flying to space, demand for cargo will increase as well.  Basically, by only funding the unmanned part of COTS, NASA is forcing those COTS competitors into markets for which there is little other non-NASA demand.Of course, NASA has lots of reasons for wanting to do things this way. NASA as an institution wants to build and fly its own rockets, and being able to continually point at a US manned spaceflight “gap”, and being able to point at other nation’s anemic manned spaceflight programs as threats, makes it that much easier to continue getting funding for their anachronistic manned spaceflight projects. Think about it. If there were one or two US commercial options for getting people to the space station, do you really think there would be as much urgency for continuing to throw good money after bad on Ares-I? Most congresspeople don’t have much of a vested interest in keeping the Shuttle Workforce humming along sucking up taxpayer dollars. But the idea of there being a “gap” in US manned spaceflight, and US access to the ISS resonates more. Especially when there is no non-NASA alternative. Take that unifying threat away, and all of the sudden convincing Congresspeople in states other than Alabama, Texas, and Florida that it’s a national priority to keep throwing billions of dollars a year keeping people in their district employed, doing something that the market is already providing, is going to be come a lot trickier.
2. The “Skin-In-The-Game” Provision: One of the defining features of NASA’s implementation of COTS under Mike Griffin’s tenure was the requirement that COTS companies match NASA funding, to “put some skin in the game”.  Jorge Frank (whose opinions I normally agree with) really liked this provision, calling it one of the best things about COTS, and stated that “It limits the field to serious providers that are confident that they have a business case for their spacecraft beyond selling rides to NASA.”  The problem is, that speaking from the record, this hasn’t been the case at all.  Look at Orbital Sciences.  They have pretty much stated that they don’t think that there’s any market for Cygnus other than ISS resupply.  SpaceX is trying to do Dragon-Labs, but even then it isn’t a big demand driver.  In both cases, they’re not expecting to make money selling their cargo delivery services to anyone else, but are expecting to make most of their money off of the new launch vehicle that will be developed in order to lift the capsule. Orbital wants to go after the Delta II market, and SpaceX wants to edge-in on the EELV market. But let me come back to that point in a second.Basically, when you combine these first two points, you can see all sorts of perverse incentives created. In order to raise a large amount of cash, you need to have a large and solid market to justify it to investors. But as I mentioned before, there’s not a big non-NASA market for cargo deliveries to LEO stations, and even the NASA market isn’t really that big, all things told. And more importantly, at the time the COTS contracts were handed out, it wasn’t obvious if a COTS competitor would actually get any of that follow-on demand, even if they delivered. Without having a realistic non-NASA source of demand for the capsule part of the equation, the skin-in-the-game requirements pretty much killed the case for anyone trying to propose doing a capsule on an existing launch vehicle. Without developing a passenger delivery capability, the only market that could justify the kind of skin NASA wanted in the game was possibly a launch vehicle market. Which is a good part of why all three of the COTS winners (SpaceX, RpK, and then OSC when RpK couldn’t raise money) were basing their actual market case on developing new launch vehicles.So, not only did the skin-in-the-game requirement make it really hard for entities that didn’t have billionaire backing (or large existing lines of business) to compete, but it also drove the technical and execution risk for the program up by biasing selection towards companies that had to develop both a launch vehicle and a prox-ops spacecraft. Low-technical risk approaches that used existing launch vehicles wouldn’t actually develop hardware that would provide enough non-NASA business to justify enough outside investment to meet NASA’s skin-in-the-game requirements.  Quite frankly, if COTS fails to deliver, there’s a high probability that it will be due to the fact that both COTS competitors need to develop both a launch vehicle and a capsule.
3. Payment for “Soft” Milestones: One of the other distinguishing features of COTS is that it is a firm, fixed-price contract, where payment is only given on achievement of specific milestones.  The idea being that in theory this gives the company a lot more flexibility on how to achieve its goals, while the government only has to pay for actual results, not just for effort.  Unfortunately, this is also a nice theory that got watered down in practice.  If you look at both company’s COTS contracts, you’ll notice that both of them make the vast majority of their money off of meeting “soft” milestones, such as performing design reviews, raising money, etc.  By the time you get to most of the hardware milestones, the government has already paid out most of the value of the contract–which greatly reduces the benefit of this approach.   In fact, if I read SpaceX’s contract information correctly, they get paid for the first two of three COTS demo flights for just getting the flight off the ground–even if it fails.  They don’t have to actually have a succesful COTS mission to collect any but the last payment.One of the key tenets of the original proto-COTS concept Gary Hudson had pitched to O’Keefe’s NASA was that other than an initial pump-priming kickoff payment, all other payments would be for hard technical milestones.  That would’ve reduced the government’s risk a lot, since until technical milestones start being achieved, it only has the kickoff capital at risk.  Second off, it would emphasize rewarding actual successful development of hardware, not just paying for paper analysis like it has always done in the past.There’s actually a fair deal of danger here for COTS and future COTS follow-ons. The worst thing that could happen would be for OSC and SpaceX to collect most of their money, and then have some high profile failures right at the end. The government would see it as having spent lots of money on small space firms, and then losing their shirt. Something like COTS wouldn’t happen again for a long time. Had they stuck to Gary’s suggestion, technical milestones would’ve been earlier in the program, and therefore, if there was a failure, it would’ve been a lot less costly to the government.

Now, I’m not saying that COTS is doomed to failure or anything like that.  I’m hoping and praying that SpaceX and OSC are able to turn this into a success.  I am suggesting though that in the future, for COTS-like programs, that it would be a good idea to make sure that “skin-in-the-game” requirements are better matched with realistic expectations on the size of non-NASA markets, that we be more careful not to bias incentives in a way that encourages larger technical risks than ought to be taken, and that rewards actual hardware success instead of paying a lot for paperwork.

[Additional Thoughts: After getting a good night's sleep, I had a few additional thoughts I wanted to tack on.  First, I wanted to point out what I think is one of the best things about the whole COTS approach--the fact that the government is giving the COTS contractors a lot freer hand in how they go about their development projects.  When you compare this to how NASA's running Constellation, you can see how big of a difference this is we're talking about.  Also, by having fixed-price payments based on technical milestones, it removes the need for anywhere near as much direct oversight, both on company accounting (a big headache for cost-plus contracts), and on the technical side.  If the company doesn't take advantage of specialized NASA resources, and ends up botching a technical milestone, they don't get paid.  The incentives all point in a lot closer to the right direction.

One other comment on the skin-in-the-game question, is to remember the X-33 debacle.  One of the main reasons why LM was given the award (instead of the DC-X team) was that they were willing to put a lot more skin-in-the-game.  The problem is, the willingness to put in money doesn't necessarily correlate with mission success, competence, or even a desire to see the project succeed!  At least one anecdote said that LM put the money in more to prevent the competition from getting something to work than because they really believed on a corporate level that X-33 was going to lead to Venturestar.  On the other hand, I am somewhat wary of giving the whole contract with no skin-in-the-game requirements, and no actual requirements to commercialize things.  While using the other useful features of COTS (firm milestone based payments, less direct overhead/interference) is better than nothing, a good part of the point of COTS was as a pump-priming exercise.  Without incentives clearly placed pushing the COTS winners towards developing these services for commercial applications, a lot of the benefit is wasted.

Lastly, the basic concepts of COTS (fixed-cost milestone-based payments, focusing on areas with a potential for non-NASA customers, etc) could actually be a decent fit for developing other pieces of space infrastructure such as depot, tugs, etc.]

By way of introducing the concept, I wanted to point out some material that LM/ULA came up with two years back that got me thinking in these directions. While many have read the AIAA paper ULA published in 2006 about various Centaur-derived manned lander schemes as alternatives to the ESAS LSAM, there was also some less-well-known material they had developed for Centaur-derived robotic landers that I found interesting. I just noticed today that a paper containing the information I had previously seen about this concept is up on the ULA site, here, so I figure it’s now ok to talk about this idea.

Basically, the second paper goes into some work LM/ULA had done for the Lunar Precursor Robotics Program back in the 2006 timeframe. They had looked into converting an existing Centaur into a lunar lander for robotics payloads, by adding a “Extended-Duration Mission Kit” and a “Lunar Lander Kit”. These kits, which the Centaur team has already detailed to some extent, would add things like better passive cryo insulation hardware, sunshields, solar panels, upgraded avionics and batteries, landing gear, landing propulsion systems, etc. The concept was based on launching the whole Centaur lander stack into LEO on an HLV.

Centaur-Derived LPRP Robotic Lander

The paper also went into a 4-person lander using the same Centaur-derived concept but extending it a bit further. A version of this concept was further discussed in the first paper. The manned lander would be two-stage with a hypergolic biprop system for ascent, and the lander would include hardware for supporting at least two-week lunar surface stays.

Centaur Derived Manned Lunar Lander

What I was interested in was what those concepts could do if they were used with in an architecture that included a LLO depot/waystation. In the case of the robotic lander, the lander itself also performs the TLI and LOI burns, which means that most of its propellant is used up before it gets to LLO. For the human lander, while they assumed the use of another stage to do the TLI/LOI burns, the system was constrained to be launchable with an Atlas V HLV, which meant that a full Centaur-load worth of propellant couldn’t be used for it either. Plus, with the use of a hypergolic ascent stage, the ascent fuel weighs a lot more than it would in a reusable scenario. Fortunately, this paper gives a mass budget, so we can do some number crunching.

For the robotic lander, it used a Centaur dry mass of 2500kg, a Extended Duration Mission Kit mass of 800kg, and a Lunar Lander Kit of about 1000kg, with 1500kg of LLK propellant, and 21000kg of Centaur propellant.  Now assume a mission concept where you tank the whole Centaur stage up in LLO, the Centaur propulsion provides most of the delta-V except for the final touchdown/hover, the hypergolic landing engines provide landing/hover thrust as well as enough ascent thrust to get the vehicle up a couple hundred meters before relighting the RL-10s for ascent.

Depot-Enabled Centaur-Derived Manned Landing Missions
Factoring in some extra hypergolic propellant for both a long-duration hover (>90s) during landing, and enough propellant to get the vehicle up to a decent altitude before lighting the RL-10s, I estimate a payload in the 7500-8850kg range (you can download a copy of the spreadsheet I used here).  The lower number was assuming a 2500m/s ascent delta-V (ie ascent DV plus some plane change propellants), while the higher payload was for a 2200m/s ascent delta-V, which is probably closer to what you would nominally need (when you have backup systems like tugs, depots, and a second lander in orbit, you don’t need as much in the way of contingency margins on any individual flight). 

By way of comparison, the mass of the Apollo LEM minus main propellants was 4200kg, and most of that was stuff that would already be provided by the lander.  So, it’s pretty safe to say you could haul at least four people up and down in such a system.  For another comparison, at the higher end of the hauling capacity, you could haul a full Bigelow Sundancer module to and from the surface. Lastly, comparing it to the two-stage lander that they analyzed, if you ditched the ascent propulsion system and propellants and used the Centaur stage, it looks likely that you could haul 6-8 people and several tons of cargo for a two week stay without much difficulty. I can check on that if I can get better numbers from somewhere of the mass breakdown for their concept–the numbers given in paper #2 aren’t very clear on which weight in the ascent stage is for stage and propulsion mass, and which is for crew accomodations, pressure shells, etc.

Note, that at that point, this is anything but a “light scout lander”.  Such a system would likely provide a substantial increase in capability compared to the ESAS LSAM, while only requiring a marginal 25-26 metric tonnes per mission worth of propellants/consumables.   I don’t have the latest ESAS numbers, but for a sortie mission from them, you’re talking at least 65 metric tonnes, for only 1/2 to 2/3 as many people.

Also note that all of this is based on the existing Centaur design, not the Wide Body Centaur/ACES stuff that ULA has been investigating over the past several years.

Depot-Enabled Centaur-Derived Cargo-Dropoff Lander Missions
Now, what if instead of hauling a crew module up and down from the lunar surface, you were just hauling one-way cargo down to the lunar surface? For that scenario, I’m getting about 23,900kg of landed mass. Which is probably enough to deliver a full Bigelow Nautilus module to the surface. Or just about any piece of equipment you could imagine. Once again, this is with a stage based on the existing Centaur stage, not anything fancy like the ACES stage.

Admittedly, getting a payload that big to lunar orbit is actually the bigger challenge. You would need to use something bigger than a single Centaur derived transfer stage like I had talked about in Part I. Solar electric tugs, multiple Centaur stages in series, or a WBC/ACES derived transfer stage would be required. Or just finding a way to offload a decent amount of weight from the module itself, and outfitting it in lunar orbit before landing it.

Anyhow, I think this concept shows that using propellant depots in lunar orbit can greatly enhance a lunar exploration/development program, while also making the transportation phase of the program much safer. This performance benefit is not just with tiny sortie missions, but also with missions much more capable than what could be done with the planned ESAS architecture. Depots just make too much sense.

The first concept I wanted to talk about was one I had several months back (and which I briefly mentioned tangentially on the blog), the concept of going to what I call a depot-enabled multi-sortie mission model. The basic concept is fairly simple.  There are lots of varied approaches you could take, but the common elements would be:

1. A LEO Propellant Depot
2. Small Lunar Orbital Propellant Depot/Way Station
3. A Reusable Lunar Lander

In fact, even the LEO propellant depot isn’t 100% necessary for the concept–it just makes everything easier.

A couple of notes on the second and third items:

1. The lunar orbital depot/way station could possibly be built around commercial modules, such as the Sundancer and/or Nautlius modules under development by Bigelow Aerospace.  I’ve got some ideas that I’ve been working on for how you could convert such modules into the foundation of a propellant depot, but with luck, I will be turning those ideas into an honest to goodness conference paper this year, so I won’t go into details now.
2. The depot/waystation would include both modules for propellant storage, as well as habitable space, and life support for two sortie crews (which depending on crew size could be 4-8 people total).
3. The depot would have facilities for long-term propellant storage (sunshields, advanced passive cooling systems, and probably some active cooling as well)
4. The landers, which could possibly be based on some of the Lunar Lander work done at LM/ULA, only need to be reusable for a limited number of times for this to make sense.
5. I think that many of the key concerns with lunar landers (the impact of dust, rocks kicked up by landing engines, etc) can probably be managed for a limited number of flights even without heavy maintenance so long as certain precautions are taken.
6. Because this is for short duration sortie missions, and because the propellant depot has long-duration storage capabilities, all stages can benefit from higher performance cryogenic propellants (LOX/LH2 is still my preference, but LOX/CH4 for some parts might still be worthwhile).  The only place where hypergols might really be necessary is for something like the lunar ejector seat I described previously.

While there are tons of possible variations on the theme, the basic concept would go something like this:

1. Once you have the LEO propellant depot setup, you send the lunar propellant depot over piece-by-piece.  With propellant depots, an existing Atlas V Centaur stage, modified with a “Lunar Mission Kit” that has a few components needed for a long duration mission, and then refueled on orbit, should have more than enough margin to place a Sundancer module all the way into lunar orbit.  In fact, if you could off-load about 3000lb worth of stuff from the Sundancer modules (might be possible if you use prox-ops tugs at both ends instead of having all the modules also be independent spacecraft with their own RCS/ACS systems, among other things), you could possibly reuse the Centaur LTV using nothing fancier than propulsive braking.
2. Send an “unpacking crew” to help setup the lunar depot/way station.  They would help unpack the modules, hookup any plumbing and wiring, verify all the systems are ready to go, and generally get things ready for exploration.  They could be sent either using a crew vehicle per se, or by a self-ferrying lunar lander as per the next item.  This crew might not need to be the full size of a landing crew.
3. Launch two lunar landers, tank them up, and then send them both to the lunar orbital station.  The delta-V needed for a lunar orbit to surface and back round-trip (with margins and reserves for plane changes and such) is pretty close to the same performance needed for the landers to ferry themselves to lunar orbit.  This also functions as a “shakedown cruise” for both vehicles, allowing you to test out all the various subsystems and verify in-space that they are properly functioning before you have to risk your life on them.
4. Start launching tankers to the lunar orbital station.  These could possibly use Centaur-derived tankage sent using Centaur-based transfer tugs as mentioned earlier for delivering the Sundancer modules.  You could probably deliver about 15,000lb of LOX/LH2 per tanker flight (about 1/4 of the propellant pumped in LEO reaching lunar orbit for a reusable system that doesn’t use aerobraking).[Update: I made a math error here, and I didn't keep the spreadsheet where I made it so I'm not sure what I did wrong. Anyhow the correct tanker delivery mass is about 7500lb for a purely propulsive system that reuses the Centaur, and about 18000lb for a system that uses partial aerobraking to reuse the Centaur]
5. Send your sortie crews once you have enough propellant for two missions.
6. Tank up both landers, and send first one to the surface for a sortie.  Continue propellant deliveries.  The second is available on-orbit to mount rescue missions.  If no rescue mission is needed, propellant can either be transfered back to the station (if enough propellant hasn’t arrived during the sortie for another sortie), or the next sortie can be launched.
7. Keep rotating landings with one crew on-orbit during one landing ready for backup, and then the next landing they’re the crew.
8. Rotate in crews on a six-nine month basis.  Rotate in new landers on a regular basis, determined by the reliability/reusability of the systems.

Basically, once you have the system setup and working, each crew will probably go on 3-4 (or more) sorties during their stint.  So, instead of having to ship out a new lander and a new capsule and a new transfer stage for each mission, you only have to ship out the marginal propellant needed for a single landing.  Depending on the details of the setup, this could possibly yield the following benefits:

1. Much higher safety.  Most of the risk in a lunar mission revolves around landing on, ascending from, and departing from the Moon.  With a depot/way station and a backup rescue vehicle, you can greatly increase the odds of getting a crew back in case something goes wrong.  In many cases failures go from being life-threatening to just plain boring.  Your return vehicle engine fails to light?  You just sit it out and wait at the lunar station for the next crew rotation.  Your lander fails to ascend?  You have a rescue mission.  You have to bail out during an aborted landing/ascent using a lunar ejector seat?  You could actually have a rescue mission on-hand in hours or minutes instead of days or weeks.  While depending on the inclination of the lunar station and the latitude of your sortie site, you might not have anytime aborts from the surface, you can at least greatly reduce the risk of losing a crew due to propulsive events.
2. Lower marginal mission costs.  Instead of making expensive hardware that mostly only gets used once, you can now eke out at least a few missions each from the transfer stages and landers.
3. Much lower IMLEO per sortie.  It might be possible to add another sortie for only a single DIV-H launch worth of propellant.  Lower IMLEO, and lower hardware costs, can give you much better bang for your bucks.
4. Lunar landing crews build a lot more experience quickly.  Of the precious few hours the six crews during Apollo spent on the lunar surface, how much time was spent just figuring out how to function in 1/6g?  How much time was spent figuring out how to work in that environment?  How to work with the tools sent from earth.  Sure you can train for some of that stuff, but there’s probably only so much you can figure out without being there.
5. More data on the impact of lunar gravity on the human body.  As I’ve mentioned before, we only have six data points that aren’t at either full 1g (billions of data points) or microgravity (hundreds of data points).  With so little data in the middle, you really can’t make any meaningful claims about how much gravity a human body really needs.  The human body could be extremely frail and optimized for 1g, or it could turn out that it works fine over a very broad range of gravity.  The fact of the matter is that we don’t know for sure, and anyone who tells you otherwise doesn’t know what they’re talking about.  By having multiple data points for the same people over time, it should be a lot easier to get good data on the impacts of lunar vs. micro gravity.

There are probably other benefits, and plenty of various nuances that I didn’t go over.  For instance, I think that coupled with a two-person architecture, like I explored in the past, you could visit a lot more sites, and do a lot more real exploration and prospecting than you could do with a much bigger crew.  But propellant depots also allow you (depending on their size) to launch larger missions as time goes by.  Even if you start with two-person crews with no landed cargo, such a system could easily expand eventually to 6-8 person crews or substantial surface cargo capabilities.  I also think that advances like orbital RLVs, WBC/ICES/ACES derived transfer stages, etc will only continue to add to the capability and flexibility of such an approach.

In short, I think this overall approach has a lot of benefits compared to more traditional architectures, and is worth further investigation.

What do you all think?

There’s been a lot of discussion, particularly at Space Cynics about ISS, its suitability for microgravity science, and the utility of microgravity research and development in general. Today, most people who have been following the program agree that the ISS has been a bit of a debacle, and most agree that the way ISS is run and the existing space transportation situation pretty much preclude any real commercially useful microgravity research from happening. However, Monte makes some useful points about the situation that while I’ve made similar points in the past, bear reemphasis. Here are Monte’s comments (with my emphasis):

(Derek Lyons) wrote:
>Which, in my book, makes the person who thinks that’s a condemnation
>of the Shuttle… an idiot. Because that was the goal of the Shuttle
>from Day One, to work with a space station.

The seemingly neat circularity emerged after the fact. With cheaper
and more frequent access, the station could have been built soon and
cheap enough, equipped and staffed adequately, to actually *do* the
kinds of research originally promised.

But with the successive delays and downscoping, that has never been
possible. Unfortunately, that has discredited the whole premise and we
get the “all we do is go around in circles in LEO” mindset, and a
vague sense that “they tried all that free-fall science and nothing
panned out” — when in fact, all but a few token bits of science have
been squeezed out by the demands of just getting it “complete” before
the oldest parts reached the end of safe service life.

(NB: I’m not claiming the most hyped promises — the giant protein
crystals, perfect ball bearings, breakthroughs in undersatnding
free-fall physiology etc — would have paid off; I’m saying there’s
never been a chance of finding out with the very limited equipment and
even more limited time available for them).

It’s as if I’d tried to build a house on a mountaintop using a
Lamborghini to carry materials and workmen. Surprisingly, the house
ends up a lot more expensive, less spacious and well-equipped than I’d
hoped… and I conclude “well, that proves a house on a moiuntaintop
is a dumb idea.”

While as Monte says, the fact that we haven’t even really had a chance to try doesn’t prove that microgravity research will ever produce real benefits, it does mean that there is a chance if things are done differently that we might get better results. There are plenty of challenges out there facing large-scale microgravity research and manufacturing, particularly due to the snail’s pace of progress when compared to terrestrial approaches that try to eliminate the need for microgravity. But I think one of the hopeful things that could come from the latest wave of commercial space endeavors is an environment much better suited towards real research and development. Between suborbital microgravity services (from existing players like Up Aerospace, and hopefuls like XCOR, Armadillo, us at Masten, etc) in the nearer term to commercial stations and free-flyers like what Bigelow is trying to do, things are starting to move in a direction where the rapid iterations that good science needs can become possible.

That doesn’t mean it will work, but it does mean that this time we’ll actually get to find out one way or the other.

In the quote they selected for the article, they mentioned my question of “will they be able to drum up enough demand to justify the flight rates they’re talking about.” Here were some of my thoughts that I shared with David Riga (the author of the New Scientist piece), that didn’t make the cut:

If he were just running an orbital hotel (he isn’t), I’d be very skeptical. Instead I’m somewhere between skeptical and guardedly optimistic. While there haven’t been large numbers of takers for flights on the Soyuz, what Bigelow’s offering is fundamentally different. Flight opportunities are frequent (which is critical for most microgravity research programs–imagine trying to run an R&D lab that you could only visit once or twice a year!), the situation is more customer friendly, training would likely be more streamlined (I hear that for Soyuz training the “passenger” is actually more of a third crew member than an honest-to-goodness passenger), etc.

It’ll be interesting to see if he can pull off his idea of forming an international astronaut corps for countries that don’t have their own space program. It wouldn’t have all the usual glory of having your own national launch system, but it also wouldn’t have the waste of it either. Countries like the UK could look at it as a smart and low-cost way of doing a manned space program–why reinvent the wheel when you can just buy a ticket and focus on doing something in space instead of blowing billions just getting there?

Also, the title of the New Scientist piece is somewhat misleading (though David may not have had anything to do with the title). There are some major hurdles for using Atlas V to fly people to Bigelow’s station–it’s just that most of the major risks don’t lie with “man-rating” the Atlas V (or whatever you want to call making reasonable adaptations for flying a capsule on an ELV). Continuing with some more thoughts that didn’t make the cut (yeah I wasn’t expecting David to use every word of my several page response…):

Most of the challenges fall into two areas: developing a market at the pricepoint Bigelow can offer with existing transportation systems (like a “man rated” Atlas V), and finding a capsule developer who can raise the money and technically execute on doing such a capsule. I think the technical risk for both parts is relatively low–this has been done before even if there are still some improvements needed over previous systems (Mercury, Gemini, Apollo, Soyuz, etc) to make it commercially viable. Most of the risk is on the marketing and financing side of things.

If Bigelow is able to start signing up high-visibility customers though, look to see that change. Once there looks like there’s going to be enough demand to justify a capsule project, I think it’ll be much easier to raise money for [developing] it.

Lastly, discussing whether I thought that the Atlas V was a good choice for Bigelow, I said:

I think at the moment they’re a pretty good choice. The good news is that with SpaceX also hopefully getting into the launch business soon, that’ll provide the competition Bigelow needs to keep prices low. Obviously, it would be great if there were high-flight-rate commercial RLVs instead, but those really need a proven market in order to justify the funds needed to pull them off. So short term, I think this may be Bigelow’s best bet. In the longer term, it’ll be up to LM to find ways
to keep themselves competitive.

To elaborate on this last point a bit, the price points Bigelow has been talking about (~$15M per person for a 1 month stay) and which a system based off of the existing Atlas V could likely deliver are probably too high for there to be a lot of space tourism demand. Fortunately, as Bigelow has mentioned a lot of times, he isn’t running a space hotel. In order to really start getting to the elastic portion of the demand curve, the price tag would probably need to be a bit lower–on the order of $2-5M per ticket (according to some reanalysis of the old Futron Space Tourism study that T/Space did a few years ago that I discussed in this old blog post). It may not actually be as impossible for LM to deliver numbers at least on the high-end of that scale as I used to think (they have some possible tricks up their sleeve if the demand for Atlas V flights was high enough to justify the investment), and if Bigelow can actually deliver on demand for 80+ people to his station in a given year it might also be enough to close the business case for a high-flight rate, small RLV. But neither of those options are likely to happen right away. So, while someone like Space Adventures could probably rent some of his facility for space tourists, at the price point they are talking about, I’d be surprised if they could fill up more than 1-2 of the 12 targeted flights per year with actual “space tourists”.

That leaves Bigelow’s “sovereign” and “prime” customers to make up the rest of the 10 flights worth of demand. Admittedly one should note that not all of the 12 flights per year are going to be people–I’d imagine that at least one will be consumables, cargo, reboost propellants, etc. And on some flights I imagine that some of the passenger seats might be exchanged for experiments, research hardware/raw materials, and other commercial cargo.

The good news is that if they’re really providing 12 missions per year, that’s a monthly flight. While that still isn’t phenomenally great for a microgravity research program (see Ken’s last post, and my last space post and these posts from the ACES conference two years back for why flight rate is important for such programs), it’s substantially better than the existing state of practice. As was stated in the first of those two ACES posts, when people know that there’s going to be a flight every month to the station, it’s a lot easier to slip last minute experiments or small hardware on-board at the last minute. Scientific research often lives or dies on iterations–on how fast you can experiment, analyze, reformulate, rehypothesize, and get to your next experimental step. What this means is that while 12 flights a year at $15M per seat isn’t perfect for orbital microgravity research, it might actually be good enough to start generating some real demand–ie the “tipping point” where orbital microgravity demand starts picking up might be a little higher than orbital tourism, and possibly high enough to fill up at least a chunk of those 10 remaining flights.

But like the space tourism demand, that demand is only going to be able to grow if Bigelow can provide enough demand for the rest of those flights. Which brings us back to the “sovereign” customers that Bigelow has mentioned on several occasions. The idea being that this would provide smaller countries a much cheaper way to get involved in manned space flight. At least one country I know of might be in an ideal position to take the lead on this venture: the UK.

As Duncan over at the Rocketeer blog has mentioned on several occasions, this might be a good way for the UK to get back into manned spaceflight as they have recently been discussing more seriously. It’s interesting to note that the premier suborbital tourism venture involves a US launch provider and a British operator, so the idea of the UK buying tickets to a US owned commercial station on US owned and operated launch vehicles could be framed as being the new way of doing things. As I mentioned above, by letting someone else spend the money on the destination and the transportation, the UK could focus on actually doing something useful with people in space, instead of blowing so much money on the first two categories that they have little left for actually accomplishing something. This would be a very forward-thinking thing for the UK to do. And if they took the lead in signing up for such a program, it is very feasible to believe that you would see other nations following their lead. I’m thinking of other Anglosphere countries like Canada, Australia, New Zealand, South Africa, and possibly even India. It wouldn’t take too many of them running small low-cost astronaut corps and doing their own research projects on Bigelow stations before you could start providing enough demand to see those kinds of flight rates. Or at least it doesn’t seem to unrealistic to imagine it.

So, at least on the surface it might be possible for Bigelow to pull this off–but he’s going to need to sign up some high profile customers sooner rather than later. In the medium and long term, if Bigelow is able to provide enough demand for that many Atlas V flights, LM is going to have a lot of competition. From SpaceX and from other corners. But that’s a problem that I’m sure we would all love to have…