Stratolaunch as Falcon9 Competition

The roll out of the Stratolaunch aircraft started a considerable amount of criticism on the sources that I read. Basically it has the same problem as the White Knight, superb aircraft with no viable rocket to mate up with. I wonder though if that is the reality.

The Stratolaunch aircraft is supposed to have a lift capacity of 500,000 pounds under that center wing. It would seem to be ideal for the three barrel launch vehicle that Gary Hudson was suggesting a few years back for air launch. Visualize a Falcon 1 heavy slung under that wing with all three Merlins the vacuum variant.  That’s just to create a visual. Now realizing that Musk isn’t involved, I go to the vehicle that I believe could exist somewhere Real Soon Now.

Paul Allen apparently went through three different big name booster companies before settling on the Pegasus. Except the Pegasus doesn’t make sense for such an aircraft. It would seem possible that somewhere there is a very quiet development effort going on. I can think of a few companies capable of developing the vehicle I am going to suggest without feeling the need to Branson about it.

When launching from over 34,000 feet, more than 3/4 of the back pressure losses from sea level are gone. This means you can have a higher expansion ratio nozzle, or lower chamber pressures, or some optimum combination of both. With lower pressure engines that still have good performance possible, pumps become simpler to develop, or even unnecessary with pressure fed by modern materials. Simpler is cheaper. Three barrels with one engine each with all large expansion ratio nozzles. Probably methane and LOX for the self pressurization aspects even at the cost of higher residual pressurant  mass than with helium. Very much an operational cost conscious design.

I start with a GLOW of 500,000 pound as maximum for the aircraft. Suggesting an exhaust velocity 3,300 m/s throughout the flight. 8,000 m/s from drop to orbit. Stage  mass of 8% at cut off.  Total mass ratio of 11.3. Mass ratio to outer stages drop 2.72. Mass ratio of core stage to orbit 4.15. Cross feed from outer stages to core until they burn out.

These are the numbers I came up with starting at the drop from the carrier aircraft in pounds.

GLOW                                           500,000

weight outer stages                     343,543

propellant outer stages               316,060

weight core stage at sep             156,456

propellant core stage                  118,798

mass in orbit                                  37,557

stage mass                                     12,516

payload mass                                25,140

It should be obvious that these peanut gallery numbers are speculation that I put together with a TI 30 at lunchtime. Real vehicles won’t hit these exact numbers as they are just what I got out of a calculator. You would need to round up or down or change the assumptions as you feel necessary to get something realistic. Look at he last number though, over 11 metric tons of LEO payload from three low pressure engines, two of which can be recovered after separation just as the Falcon9 first stage is recovered now. Actually simpler as the Stratolaunch will be from up range so that the outer boosters RTB (Return To Base) without needing a boost back burn. The Falcon9 is rated for more payload than this, but before shouting too loud, I suggest going back and looking at the actual loads orbited and find that every one of them to date is well under what I have speculated here.

Cost could beat the Falcon9 depending on assumptions. An aircraft to maintain instead of a launch pad. Two simple engines and small stages to refurbish before next flight against nine engines and a larger stage. An expended core stage comparable to the Falcon9 upper stage though simpler by design.

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Sending the Probes

Before embarking on settlement and exploitation missions, the distant targets need to be investigated. It would be sad to spend major bucks developing one NEO only later to learn that another one has better concentrations of whatever you are interested in as well as being in a more convenient orbit. It would also be unfortunate to focus on Mars for instance only to learn that another destination suits your purpose better, and vice-versa.

One solution is to send a lot of inexpensive probes to every destination that just might be of interest to you, or anybody that might be willing to buy the information from you. Cassini was impressive, at the Saturn system, told us nothing about about anywhere else. In order to exploit and settle the solar system, we need a wide body of information about everywhere.

Advances in electronics and communications have reached the point that a 10 kilogram vehicle of 2017 is far more capable than one of the massive missions of yesteryear. The trick is keeping them affordable, and transporting them to places of interest. I suggest that the answer to both could be a fairly small rotovator. A rotovator in an eccentric orbit to Lunar distance would be at just under escape velocity at perigee. It could pick up a probe with no significant propulsion from LEO and sling it to well above escape velocity with no onboard propellant used. The rotovator could recover lost momentum with high efficiency electric propulsion. In this way, the probe uses a multi-ton propulsion system that it leaves behind for future use.

A 3 km/sec rotovator is a bridge too far for a first generation system. A solution is to find less challenging work to learn on. A thorough investigation of the Van Allen belts might be an early challenge for the adolescent rotovator/probe system. A group of small probes is carried into LEO as a secondary payload. The rotovator with just a few hundred m/sec intercept velocity picks one up and slings it to an eccentric orbit through the belts. Reboost and repeat as often as feasible.

Next step is to raise the eccentricity of the rotovator a bit more and start sending probes to GEO and Lunar orbit. Repair vehicles and tugs to GEO could be a market as well as units dedicated to nudging dead sats out of GEO into a destructive reentry orbit. The ones to Lunar orbit could get low and expendable to map with a precision only dreamed of today. Other probes could hit the L points for various reasons.

When the rotovator/probe system is more mature the eccentricity is raised again to nearly escape for the distant probes mentioned earlier. One a week departing at almost 3 km/sec above escape could explore most of the solar system with just a little gravity assist. Fifty deep space probes a year should get the job done, or more rotovators could be orbited to up the tempo. One thing that would be explored here is the fast passages to Venus and Mars as this is a much hotter velocity that the propellant limited exploration vehicles to date.

The rotovator itself should mass about a ton. The solar panels and electric propulsion about two more. Total mass being under four tons and quite compact in launch configuration, it might ride share to orbit on an F9, Atlas, or Ariane.

The rotovator experience would be valuable in itself of course. One in Lunar orbit could land loads from Earth and pick up stationary loads from the surface without burning propellant. Others at Mars, Venus, and scattered through the solar system coe the transportation hubs only dreamed of t the present time.


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A Personal Space Program

Assuming that I reached the point of controlling enough resources to do a serious space effort, how would I do it? Note that the question is, “how would I do it?” Enough resources to me means that I either own a billion dollars in disposable wealth, or have a combination of personal wealth and targeted investments that I control.

The first thing I would do is invest most of the money in a relatively safe place while investigating what to do, how to do it, and who to do it with. There are hundreds of ideas per good idea, and hundreds of good ideas per idea that would be useful to whatever I came up with. First hire would be a librarian/researcher or several to search prior art on any avenue I happened to find interesting.

I would downplay information about my available resources as much as possible. I was at a conference in the early 2000s talking to somebody when he looked over and saw John Carmack. Instantly our discussion was over as he headed that way like a dog after a rabbit. There is a reason that many wealthy people stealth their net worth. I would have no problem being quite rude to people demanding that I follow their particular dream instead of creating my own. Many of the bad decisions I have made in business and life are because I assumed that some adviser knew what they were talking about.

I would start by having the librarians look for every potential revenue source that anybody has ever suggested. Everything from helium 3 mining, to tourism, to SPS, to interstellar probes, everything. Initial investment only lasts until it runs out, then revenue is required. Sorting the possible wheat from the probable chaff would start immediately and continue as long as the program lasted. Some seemingly lucrative concepts would be duds, while some stupid schemes would be winners. Keep a constant lookout for good and bad directions. Business steering is more important than technical steering.

Second would be research into potential suppliers, partners, and organizations with similar goals. The idea is that some things will need to be done in house while some thing are better outsourced. The criteria for dealing with an outsource would be integrity as well as technical competency. An outsource that has lived on phase one SBRs for decades with never a follow up is likely to be a bad one to deal with, not definitely, but likely. On the other hand, one that has been very productive but has a reputation for shady dealing could be even worse with them using a minor variant to compete against me and possibly destroying my portion of that market.

Third would be looking into technical solutions with  the cheapest methods possible. Obviously I would prioritize my own ideas, but would attempt to be open to other concepts. On this blog I have suggested several compensating nozzle ideas, several rocket pump concepts with novel engine layouts, and a bunch of ideas with tethers, airframes, and other stuff I have little or no real world experience with. Research into prior art would be critical to this step with many ideas either busted in concept or patented  by others, either of which would be a show stopper.

Moving to hardware, I would look for the least expensive ways possible to verify concepts. It may be that I would need to hire experienced people, or it may be that it would be better to partner with a group that is already up and running. An XCOR or Masten class connection would possibly be more cost effective than starting from scratch. Modest R&D money plus a percentage of ownership would prove or disprove a lot of concepts in a short period of time. It is my opinion that a compensating nozzle would be easy and fast while boosting payload by several percent and easing combustion chamber requirements. I also believe that a very high pressure engine is possible with some of the integrated pump concepts I have suggested over the years. The idea is to find out on the cheap without committing to risky tech ideas. Several airframe ideas could be checked out with the home built aircraft community. I supply materials including engines and they build the experimental aircraft that they own after I get my information.

After getting the information from the engine and airframe people a decision is made whether to build in house or buy launches. What destinations and business opportunities exist in LEO and beyond would influence the decision as well as costs and availability of transportation. Buy from ULA or SpaceX may or may not be a good business decision. It’s not a slam dunk either way unless internal capabilities are known. My opinions about engine and airframe design may give a major advantage, or they may be the ignorant fantasies of a dreamer. It is important to know first. Beal, Branson, and Allen come to mind at the moment as smart people that have spent large sums on questionable decisions.

If everything has been done properly to this point, expenditures  should have been under $10M. The invested money should have returned more interest than that during this initial phase. The librarian/researchers should have a suite of possibilities worth looking into. Now the heavy investing starts.

Wherever the goals may be in LEO and beyond, humans will eventually be involved. On the ground, a high RPM test rig determines ability to adapt under various arm lengths, RPMs, and restraints to prevent head turns that tumble the inner ear. A partial gravity primate test rig in LEO should be early on the list of things to build. It is important to know if health can be maintained at 0.16 or 0.38 gee without an intensive exercise program. This has been neglected for far too long. If a short arm and low gee section could maintain health, it would make no sense to make bigger and riskier centrifuge wheels, and even less to crap shoot microgravity conditions for long trips. A probe to the moon with a drill and radiation detectors to determine the regolith shielding depth required for various duration missions. The drill hits a depth of ten meters with radiation detectors every few centimeters. Several locations to characterize  dosage at various depths, sun/GCR angles, and materials.  This information would be useful on Mars and LEOs as well. A greenhouse in LEO for intensive study of plants for food, oxygen, and recycling is needed.

There are a number of possibilities for in space propulsion that could save fortunes compared to current options. Depots, tethers, beams, pellet streams, and high ISP options all need to be checked out before the next steps are taken.

By now, it should be obvious which are the best available options for launch to LEO. The best available way to keep people healthy. Methods of travel beyond LEO have been narrowed down to more economical methods than conventionally available. Probes to Luna or NEOs or other planets have found useful and profitable reasons to go. It would be interesting to see what would have appeared by this time.

It is my opinion that Lunar development would be early on the list. A farside radio telescope is on several wish lists. Boots in dust tourism and exploration. Mining for volatiles and minerals useful in space.  NEOs for many reasons. Check out a few competing SPS concepts. A rotovator slinging hundreds of small probes to every destination of interest. it could be interesting.


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Quantifying Public Support

We quite often have someone suggest that some program or destination should be pursued because it has public support. Or that some project should be started to increase public support. My questions are, “what is public support exactly?” and “how does it affect the goals I think important?”

There are varying levels of public support, most of which have very little to do with accomplishing anything important in space. One level is someone choosing to watch something space related on television instead of another Friends rerun. I fail to see how this level of support generates much in the way of useful work. How many of these does it take to equal the effect of one Musk?, millions?, thousands?, tens of millions?…I would suggest x10^8 or so. How many to equal a Goff, Greason, or Carmack? IMO, the spectator public has very little to do with progress in spaceflight except occasionally voting against shutting down some jobs program, and might even be considered a negative in some of those cases.

Perhaps a level up from the couch potato in public support is the talkers like me and some of the ones I argue or discuss things with from time to time. Some of the talkers are doers, but it is hard to tell which ones unless paying real attention.  Realization of x10^7 of us to equal the effect of one of the real players is a bit humbling to us near spectators. For most of us at this level, $ome lack of ability is usually involved, even if it could be worked around with more motivation. However, moral support is often neither.

In my opinion, public support is often vastly over rated. The public support for SLS/Orion is still likely ahead of that for Falcon9Heavy, and even further ahead of Vulcan, New Glenn, or any of our other favorite launchers or launchers to be. Public support though, doesn’t seem to have much effect on launcher manufacture or dropped LOX domes.

Before Falcon 9, and especially before Falcon 1, public support for SpaceX was close enough to zero to be lost in the noise. Before New Shepard, how much for Blue Origin? How much does public support affect ULA unless there are jobs or votes involved?

I’m good with somebody proving me wrong. I would like to think my effect is more than 1/x10^7 of a real player. I am not good though with more people just asserting that the spectators/public are super important for some reason.

To me, the public support that counts is when a customer plunks their money down. Whether it is a satellite launch or a hamburger, paying customers are the ultimate measure of useful public support.

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Random Thoughts/Rocket Legos: Masten Xephr as a Vulcan SRB Replacement?

I’m sick at home today, so had extra time to think about fun technical concepts, so here’s an interesting one to think about. Right now, ULA’s plans for Vulcan include using expendable Orbital ATK GEM 63XL sold strapon boosters to enable higher performance missions, as shown below.

Vulcan Centaur Exploded View (credit ULA)

Here’s my crazy thought–what about a future upgrade replacing the expendable solid-fueled strapon boosters with fully-reusable VTVL liquid-fueled boosters?

Here’s some thoughts/considerations:

  • The boosters usually stage pretty early in the flight, just like the side boosters on Falcon Heavy, meaning that the required dV for boostback and landing are fairly modest, probably enabling all landings to be RTLS land landings.
  • Historically people have estimated that the cost per booster is in the $5-10M range. With a fully reusable booster stage, a much lower number should be possible, meaning that heavier Vulcan flights would be a lot cheaper than otherwise.
  • The GEM63XL has as best I can tell ~450klbf of liftoff thrust. That’s right in the same size range as the Masten Xephr XS-1 concept1, which has ~7x 65klbf engines last I saw.
  • A LOX/Methane stage like Xephr would have ~20% higher Isp than a solid stage, and being pump fed, even with reusability is likely similar or better pmf, meaning there’s a good chance you could still provide the same impulse to the Vulcan stage while maintaining enough prop for RTLS maneuvers.
  • I’m a bigger fan of VTVL powered landing than SMART reuse, but for missions like this, the core booster would be going so fast at staging that recovering just the engines might not be a totally awful approach.
  • It might be possible to design the Xephr boosters to serve both ULA Vulcan strapon booster markets, as well as flying their own expendable or fully-reusable upper stage (for much smaller LEO payloads–maybe in the 1mT class). The strapon booster market would mean you’d want to have a small fleet of 8-10 of these boosters, and ULA would only be using them a few times a year, meaning that the rest of the time you could have them flying smaller payloads such as propellant (enabling lower cost ULA distribute launch), megaconstellation satellites, or cargo deliveries to space facilities.
  • The current Xephr concept already used parallel staging of the upper stage, which would be attached via struts much like strapons are attached onto a core stage. Would it be possible to design the struts to work for both applications?

    Masten’s XS-1 Concept Xephr (credit Masten)

There are a few challenges that would need to be addressed to make this work though:

  • Solids don’t have a lot of propellant on them compared to a liquid fueled first stage like Xephr. GEM63XL has a GLOW of ~117klb, in spite of having 450klbf of liftoff thrust. It might be possible to partially load the stage for Vulcan boost applications to provide more thrust to the main vehicle. Though this will require some optimization and analysis to see how best to balance things.
  • Another challenge is that Xephr is probably more squat than the planned GEM63XLs. Right now some of the pictures show the boosters evenly distributed around the stage, but others have them clustered tightly together on both sides. It would be relatively easy at this point to change the spacing on the boosters, but will become significantly more expensive to change down the road.
  • Another aspect of the fine aspect ratio of the solids relative to the Xephr stage is that it might force you to a higher aspect ratio booster than Masten would ideally like, in order to keep the attachment points the same. Though the LOX/Methane stage is lower density than a solid so it might still be tall enough, just wider. Once again, more analysis and optimization would need to be run.

All told, it’s an interesting idea that would be worth running some numbers on. None of the challenges are obvious show-stoppers, but the devil is in the details. This concept would make Vulcan more competitive down the road, and could potentially have a lot of additional synergies between the two companies. This also would provide a company like Masten with an existing anchor customer for a Xephr-class reusable first stage. Rockets aren’t Legos, but during the early design phase, there’s a lot more flexibility to easily accommodate crazy ideas like this.

Posted in Launch Vehicles, MSS, Random Thoughts, Rocket Legos, ULA | 7 Comments

Random Thoughts: RLVs and Megaconstellations

Last month I was out in Washington DC for a satellite industry conference (the 2017 Satellite Show). My startup has been working on a cool satellite servicing related project that I need to blog about soon, and we were out there to meet with potential customers, visit friends, and try to find new opportunities to pursue. While having dinner with one friend, who is a lot better connected with the satellite industry than I am, we got discussing an interesting thought about future market dynamics, that got me thinking. I’d like to share an abbreviated version of this thought, to see what people think.

Anyhow, by way of introducing the topic, right now there are several companies proposing massive fleets of LEO telecomms spacecraft. If you believe all the me-too filings with the FCC, there are nearly 20,000 new proposed spacecraft, all that would theoretically be launching within the next 10 years. That’s over an order of magnitude more spacecraft than are currently flying. Now, many of those are going to fail, but I think there’s a non-zero chance that we could see at least a few make it into successful operations. We had a similar wave in the late 90s, right as I was starting to get seriously interested in the industry, and in the end only a few of the proposed constellations of that time panned out (Iridium which had to go through bankruptcy but is now launching its second constellation, and Globalstar, and Orbcomm), but I do think there are some fundamental differences that give this round a better shot. There are a lot more affordable launch options coming up–not the least of which is SpaceX, technology especially on the electronics side has dramatically improved, there are shifts in how people consume telecomms products/services that make it easier for comms providers to reach customers, and some of the providers have raised very serious amounts of capital. That still doesn’t prove that SpaceX or OneWeb or Boeing will succeed, but it gives me some hope.

For the first round of megaconstellations, I’d give OneWeb the best shot of being first to market with a big LEO constellation (>100 satellites). By way of disclosure, I’m a bit biased since we’re actively talking with them and some of the others about some services we’re trying to provide, but I still think it’s not much of a stretch to see them as likely being first to market. They’re going after an ambitious but IMO realistic technical approach, that doesn’t have all the bells and whistles SpaceX is trying to cram into things. They’ve raised $1.7B of the ~$3.5B they need to make to market. If I’m not mistaken, they’ve raised enough to cover the development and production of their spacecraft, and most of what they still need to raise is just for the launch of the main fleet. They also have a lot of people who have been working on this idea for years, and who know their way around this industry. No guarantees, and no guarantees they’ll be successful in the long run, but if I were a betting man, I wouldn’t be surprised if they actually made it into operations.

But their biggest competitor is SpaceX. And while OneWeb may have the first mover advantage, SpaceX has an important advantage for second generation systems–they also own their own in-house low-cost launch system. You don’t have to fawn over every tweet Elon types to believe that they’re likely one of the cheapest launch providers in the world right now, and that their launch costs are probably significantly lower than anyone else’s launch price1. This gives them an inherent advantage, especially for a second generation. Even if other megaconstellation developers fly on them–they’re going to be paying the full price, while SpaceX only has to charge themselves their internal launch costs.

Is this an insurmountable challenge for OneWeb, Boeing, Kaskilo, and the others? I don’t think so. But it does suggest that in the long-run they may need to find a way to get a similar advantage. What that suggests to me is that for the second generation of LEO megaconstellations, the ones most likely to stay competitive with SpaceX will be the ones that find a way to duplicate their in-house launch cost advantage–by pairing-up and vertically integrating with their own low-cost launch provider (preferably an RLV developer). By doing so they can negate one of SpaceX’s biggest advantages in a way that might give Elon a serious run for his money.

So if this hunch is right, what are the options? Basically you need to do something that gets your launch costs below SpaceX’s published launch prices, even with reuse starting to have at least a modest price impact. I can think of a few approaches:

  1. Approach Blue Origin about a merger. While Blue Origin is seen as the most likely RLV competitor to SpaceX, this may be a challenging deal. You’re basically trying to merge with a company run by one of the richest people in the world, so it would likely be more of a “please Jeff, buy us out and let us keep at least a part of the resulting company”. It’s possible, but seems like a bit of a meh deal for a megaconstellation developer. Especially if they were able to get a successful first generation system up and are trying to stay competitive for the future.
  2. Buy out one of the small launch vehicle developers (VirginOrbit, RocketLabs, Ventions, Generation Orbit, Vector Space), and try to get them to scale up a bit and get into reuse. This one seems a little more plausible. You’d be taking a team that hopefully by the point where you’re acquiring them, they’re starting to fly regular space missions, and then doing what Elon did, and trying to convert an expendable vehicle into a more and more reusable vehicle. You don’t necessarily have to go to the full scale Elon did–if you’re just trying to have a way of launching your own satellites, you don’t necessarily have to go after an EELV class vehicle. In fact a ~0.5-2mT to LEO semi-reusable vehicle might be competitive enough with SpaceX to at least be cheaper costwise than paying their launch price, and would still allow you to launch several LEO megaconstellation birds per flight. One challenge is that at least the bigger of this group (Virgin Orbit and RocketLabs) have already raised a significant amount of money, and have pretty high valuations–you’d be paying pretty dearly for one of them.
  3. Roll your own RLV company. If you’re a successful 1st generation megaconstellation developer, you’ll hopefully have some non-trivial profits coming out of your operations going forward. These constellations are hoping to be chasing multi-billion dollar market opportunities. Which means that you could eventually spool up your own in-house launcher capability. But you’d be starting from scratch, trying to hire and build a team. It’s definitely possible given enough money, but seems like it would likely be a slow and painful process.
  4. Buy someone like Masten. I listed this one last, because as a shareholder of Masten, I’m obviously not an unbiased source2. But there’s a lot to be said for buying a company that has significant rocket development and operations experience. Sure, Masten has mostly been focused on low-altitude EDL work till now, but a lot of that has been due to being too undercapitalized to make a serious go at full suborbital flight. They have significant rocket development and flight operations experience. They haven’t done multiple VC rounds at unrealistically high valuations. And their focus has been on developing fully-reusable, gas-and-go launch vehicles. Not expendable vehicles with reusability powder sprinkled on them. With something the size of their Xephr XS-1 concept vehicle (or potentially a little smaller), if they could pull off a fully-reusable vehicle like they think they could, that could potentially be very competitive with SpaceX. Definitely cheaper than their launch price, maybe even creeping up on their launch cost.

Notice I didn’t say “go start another expendable small launch vehicle company” like far too many people are doing (and somehow raising money to do). I think you’re going to have to go in for at least partial reuse, if not full reuse to have a shot at getting close enough to stay competitive. I think there’s a lot to be said for looking at one of the smaller launcher companies that doesn’t yet have VC-inflated valuations (Masten, Generation Orbit, and maybe Ventions or Vector Space). A lot more of the money can go into scaling up and developing a competitive system, and while most of those companies are small, they all have at least some critical mass to them.

And if you had a small fully reusable launch vehicle, there are also a bunch of other markets you could serve above and beyond launching and replenishing your own constellation. Stuff like propellant launch for companies like ULA who want to do Distributed Launch, launching cargo or people to commercial LEO facilities (that might not be able to afford COTS-scale vehicles, or who might be interested in more frequent up/downmass opptys), space tourism, or launching materials for building large LEO, MEO, or GEO spacecraft and space facilities.

Anyhow, it’s food for thought, but while LEO megaconstellation developers start getting traction, I think it would be well worth it for them to start thinking about how to pair up with a promising launch vehicle developer that can help them stay competitive with SpaceX. Unless they really want to have SpaceX eat their lunch on the second generation megaconstellations.

Posted in Blue Origin, Business, Launch Vehicles, MSS, Random Thoughts, RLV Markets, Space Transportation, SpaceX | 12 Comments

Fairing Hat Trick

It would appear that the first stage operational reusability is happening for multiple companies in the near future. The next step seems to be fairings and second stages coming back for more employment. It seems to me that there may be a possibility to use one to assist the other if there is enough payload margin. I am suggesting that the fairing be kept with the second stage all the way into LEO, or possibly even into GTO.

The payload fairings on most vehicles seem to be more expensive and robust that I had been aware of even a few weeks ago. I am going to suggest incorporating a heat shield into the fairing and using it to protect the second stage through reentry. It would appear that the mass of fairing and second stage would have a fluffy enough reentry profile that the heat shielding material would be a fairly minor mass hit compared to those on vehicles with higher density. The main mass hit would be that of carrying the fairing through the whole mission rather than the normal jettison at low enough dynamic pressure.

fairing                                                                                         At payload separation, two arms on the second stage lift the one piece fairing off of the payload exposing it to space. That is cartoon 1 on the left with the arms in green. The arms flip the fairing around and pull it up over the engine and tanks as in cartoon 2. At reentry the stage is fully enclosed in the fairing with the engine mass forward in the pointy end as in cartoon 3. If it can be done this way, the second stage would see very little thermal stress during reentry and has the possibility of gas-n-go seriously enhanced.

Bonus points with the arms would be if they could be used for deploying solar panels and antennas for the spacecraft before deployment saving a bit of risk and complexity. More bonus points if the arms could also be used to deploy parachutes or other recovery gear at the lower altitudes.


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Laundry in Microgravity

The lack of laundry facilities in orbit was brought up recently and it occurred to me that  this lack seems to be more for lack of trying than real difficulty. The lack of trying that I suspect could be because it is more trouble than it is worth to wash clothes on the ISS when it is a relatively minor mass and volume is to just throw away the dirty and ship up more from time to time. Eventually with enough human activity in LEO and BEO though, the choices will be wash, wear dirty until worn out, make more on board, or ship increasingly large quantities of disposable clothing from Earth. I think option one will be desirable at some point.

The problems with washing clothes in microgravity as I understand it are more to do with the chemicals normally used in detergents than with mechanical problems. The chemicals from the detergents and most soaps are very unwelcome in a closed environment as any environmental contamination is a major issue. It’s not like the air conditioner is going to vent problems outside the laundry room.

To me, the likely solution will be more mechanical with plain water than the soaps and softeners we use here on the ground. Something along the lines of pressure cleaners allied with old style wringer washing methods.

laundryIn this cartoon, he dirty laundry is fed into the rollers on the left. The rollers seal the entrance and feed the clothing into porous chain that travels through the cleaning area where it is hit from both sides by staggered nozzles that are calibrated to have enough pressure to knock dirt loose from the clothing but not enough to damage it. The clothing exits the chain through a second set of rollers that squeezes  out most of the excess water and seals the exit from the rest of the ship.

During this the fluids in the wash area are continuously recycled through a liquid air separator/dirt filter/pump so that the same water is used indefinitely. This is represented by the oval in the lower section of the box. Second function of the filter/pump/separator is to maintain a lower pressure inside the machine than in the rest of the station so that there can be no contamination escape to the living area.

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Random Thoughts: First Pass Analysis of a White Dragon/Xeus Lunar Sortie Mission

After yesterday’s SpaceX announcement of having booked two customers for a Apollo-8 style mission around the Moon and back, using Falcon Heavy and Dragon V2, I got thinking about ways to take the next step in lunar tourism–surface missions. Now, this “White Dragon” mission around the Moon makes a lot of sense for SpaceX even though Elon doesn’t care that much about the Moon:

  1. Hardware-wise, there really might not need to be much new work beyond what they’re already doing for Falcon Heavy and Dragon V2. The flight is short enough relative to a worst-case ISS delivery that with 2 passengers instead of 7, the ECLSS is probably already adequate. The heat shield, due to minimum gauge issues with PICA-X, is way overbuilt for LEO return, and thus is likely more than adequate for lunar return.3 The Falcon Heavy should have the throw-mass to do the mission. So they can do this without likely requiring dramatic hardware development beyond what they need for normal FH and crewed Dragon V2 flights.
  2. It’s revenue–even if it costs say $170M/flight (take a ~$140M cost for a four-person ISS delivery, subtract 60M for the Falcon 9 and add 90M for the Falcon Heavy), they can still get takers at a price of ~$85M each. Heck, even if they’re selling it through Space Adventures for $100M each (with the $15M delta being Space Adventure’s cut), this is still a good deal for SpaceX. They only have to convince two people, and they get double the revenue of a Falcon Heavy flight. That’s not quite as good as selling a several flight campaign for Iridium, but it’s not too shabby, especially if Space Adventures or someone like them is bringing the passengers.
  3. There’s a good chance it could turn into a steady stream of revenue. As I’ve previously discussed here, one of the main limitations on space tourism has been availability of spare Soyuz seats, not the price. And when you add the novelty of a lunar mission, I wouldn’t be surprised if they could get a steady White Dragon mission every year or every other year at worst. Even if the price doesn’t come down much over time.
  4. It gets them experience they want for future deep-space operations. Testing reentry heatshield wear, ECLSS behavior on long missions, how their electronics hold up outside the magnetosphere, etc.

So for all those reasons, it makes sense for Elon to say yes to White Dragon missions, even if he doesn’t care at all about the Moon. If someone wants to give you money like that, and it doesn’t cost you much to service them, why the heck not?

But as soon as you start talking about lunar landing missions, the situation changes. Now you’re talking significantly more complicated missions that are going to take non-trivial amounts of new hardware, that will unlikely be directly relevant to Mars missions. Barring someone dropping a bunch of money in Elon’s lap, I’m not sure it would make sense for SpaceX to do the mission by themselves. But, it might be an intriguing joint mission for SpaceX and ULA, assuming for sake of argument that Elon would be willing to work with his closest competitor, and that Boeing and LM wouldn’t torpedo something that could be seen as a direct competitor to SLS/Orion.

So, assume away the political challenges for a second. Could you realistically make a lunar landing mission work with a combination of SpaceX and ULA hardware? After running the numbers, I’d say tentatively yes.

Here’s what the SpaceX stack would look like:

  • Falcon Heavy
  • Large LOX/LH2 tanker (~39.4mT of prop, ~7.2mT dry)
  • Dragon V2 on top

The ULA stack would look like:

  • Vulcan/ACES 546, with the ACES having a Xeus landing kit (~1mT)
  • Small short-duration two-person crew cabin (estimated ~2mT)

Falcon Heavy would launch first, placing the crew and tanker in orbit. Vulcan/ACES would then launch shortly thereafter, with ACES performing a rendezvous with the SpaceX stack, transferring ~39.4mT of prop over (basically filling the ~70mT ACES stage). The Dragon would then separate from the tanker, and connect to the ACES/Xeus stage. The ACES Xeus stage would do a TLI burn for the stack, followed by an insertion into LLO. Dragon would then be left in orbit while the astronauts are flown down to the lunar surface by the Xeus stage, hang out for a while, and then they get flown back up to LLO by the same Xeus stage. The Xeus stage would then dock with Dragon and perform the LOI burn, sending the whole stack back to earth.

Using these assumptions, it looks like the concept closes (here’s the first-pass analysis spreadsheet: WhiteDragon-XeusCalcs), but without as much margin as you would want, and without enough propellant to propulsively capture Xeus back into LEO.

Here are some ways that the concept could be improved:

  1. Be more aggressive on the lander cabin design–2mT is actually half the dry mass of a Dragon Capsule, in spite of not needing anywhere near the capabilities–no need for a trunk or a reentry shield, no need for RCS engines (ACES and Dragon V2 both have plenty of maneuverability). So you might be able to whittle that down a bit.
  2. Use chilled propellants–between the Vulcan/ACES 546 leftover propellant and the Falcon Heavy tanker propellants, there’s actually more propellant than will fit into a stock ACES stage at normal boiling point densities. Chilling the propellant would both surpress boiloff losses, and would also allow you to cram a bit more propellant into the stage. This is already something SpaceX does for Falcon 9, so it isn’t that crazy.
  3. Stage in EML2 and have the Dragon V2 perform the earth return burn leaving Xeus at EML-2. The question is how much propellant is needed for rendezvous, reentry, and landing. By my BOTE calcs, assuming a 320s Isp on the regular Dracos, you should be able to get ~620m/s of delta-V out of Dragon V2, and you’d only need ~150m/s for the earth return/powered swingby maneuver. But you’d now be talking about a much, much longer mission.
  4. Jettison the lander cabin and/or Xeus kit prior to the earth return burn.
  5. Have the lander cabin actually be a separate lander/ascent stage. Have the ACES stage not have a Xeus kit, but do an uncrasher maneuver where the crew cabin stage separates right before landing. the ACES stage returns to lunar orbit w/o the ascent stage, and reconnects with the Dragon capsule. The ascent stage lands, the crew hangs out for a bit, and then launches again back up to the waiting Dragon and ACES stages. The crew cabin/ascent stage is left in LLO before ACES takes Dragon back to Earth.
  6. Down the road adding refueling in LLO or EML2 or on the lunar surface would make the whole thing tons easier–you’d need another launcher, but that would all of the sudden give you the margin needed to do much more ambitious missions if you didn’t have to haul the prop all the way from LEO and back.

There are probably other variations on the theme. But the interesting thing is that this concept comes close to closing using Falcon Heavy, a stock Dragon V2, with the main pieces of new hardware being a propellant tanker section for Falcon Heavy4, the Xeus kit for ACES, the fuel transfer hardware, and the crew cabin.

If you assume $150M for the Vulcan/ACES 546 flight ($90M for the bare Vulcan/ACES plus six strapons at $10M/ea), $170M for the FH + Dragon V2, $20M for the tanker/transfer hardware, and $30M each for the Xeus kit and the crew cabin, you get about $400M/mission, or about $200M/person (plus markup if your brokering it through Space Adventures). Call it an even $250M/person ticket price. That’s about 1/3 of what Golden Spike was targeting…

Anyhow, rockets aren’t legos, who knows if Elon and ULA can play nice with each other, I have no idea how ULA would get its parents to go along with a scheme that enables lunar landings without needing SLS/Orion. But the concept comes really close to closing, so I thought I’d put it out there.

Posted in Commercial Crew, Launch Vehicles, Lunar Exploration and Development, Propellant Depots, Random Thoughts, Space Exploration, Space Transportation, SpaceX, ULA, YHABFT | 51 Comments

Refueling for the Secondary Mission

It is fairly obvious that there are many benefits to having refueling capabilities in space. Perhaps not to the monster rocket fanatics with blinders and a few others, but to most of us it approaches no-brainer territory. The problem is getting to the first egg. The first bird we would accept as a chicken came from an egg, but that egg did not have to be laid by a bird we would accept as a chicken. Mules do not have mules for parents. The first refueling capability doesn’t have to have depots in the business plan, perhaps a buddy tank for starters.

The problem with getting refueling capability in space is often called a classic chicken and egg problem. Without a depot there is no refueling capability or reason to build vehicles to use it, and without the vehicles to use it there is no reason to build a depot. Dual launch architectures try to get around this by designing missions around a propellant launch and a mission launch. So far, this hasn’t worked well either as the mission planners try really hard to avoid boxing themselves into a corner where if either launch  fails, the mission fails.

One possibility hinted at in comments a while back is to have the primary mission fully capable of success if the primary launcher works properly. Then have enhanced secondary capability if the propellant launch succeeds and can top off the tanks in the primary. It took me a while to wrap my thoughts around the concept, after which I started working it over to see what I could think of. I can’t give due credit to the original thinker because I didn’t really grasp it until days later, just that it was somewhere in the 40 depot posts by Jon Goff and hundreds of comments associated with them. The originator can chastise me in comments  for not digging back for is name.

So this is my take on the idea. A vehicle arrives in LEO with payload for LEO. It hits the refueling vehicle either before or after placing its’ primary in the correct orbit. It off loads any excess propellant it managed to bring up if it is going to deorbit, or if it simply has excess for the secondary planned mission(s). Alternately it accepts enough more propellant to accomplish other missions that are non-critical to the primary mission.

The secondary missions suggested were along the lines of deorbiting various dead satellites. Surveying satellites with minor issues with the intent to design possible repair missions. Rendezvous with satellites in useless orbits and boosting them to the proper orbits. Creating the capability of the upper stage herding dead GEO sats after a GTO burn for the primary customer. Testing servicing options that would be too expensive for a dedicated launch.

The whole point would be to have some capabilities in place and in use for the cost of one launch that did not have to satisfy any customers other than the company that launched it. It would be replenished with excess propellant in vehicles that didn’t need all they hauled up. It would refuel various company vehicles that were scheduled to do extra work for revenue. The refueling wouldn’t have to be a maximum top off, just a calculated amount for individual missions. By using the capability in house, the problem of selling to and satisfying outside customers goes away. By not putting the capability in the critical path, the primary customers should have very few concerns about endangering their ROI.

It would seem that a capability could be started in the two digit millions. It could be very crude with perhaps LOX only to start, or LOX/Kero, or hypergolics, just as long as it fit that particular companies’ business plan.

Later on it might be possible to put this in the critical path of missions because a solid experience base and track record had been built up. Then after that it should be much simpler to get true multi-propellant depots up and running with whatever the market expresses a need for.

Posted in Uncategorized | 17 Comments