Reusable Falcon Heavy payload (upper stage staging velocity)

Jon and I were discussing the recent Falcon Heavy payload numbers.

Expendable performance to GTO is supposed to be 22 tons (metric, same for the rest of this post). Given how aggressive that is, and given the history of Falcon 9’s performance, I would expect that to be to 1800m/s-to-go (i.e. you need 1800m/s more delta-v to get to actual geosynchronous orbit). The delta-v between that and LEO is approximately 2.5km/s, though that depends on the details of exactly which LEO orbit (but I think this is a good number; provide a better number if you know of one).

Assume the propellant in the upper stage is about 110t, and the dry mass is 5t (this is in range of other people’s estimates and figures from SpaceX, though I’ve seen down to 4t dry mass). With a 22t payload, that gives a full mass of 137t, empty of 27t. Given Merlin Vac’s Isp of 348 (which is staged-combustion territory, although it is gas generator), you have a bit better than 3.4km/s exhaust velocity.

Delta-v of the upper stage is thus slightly more than:
3.4km/s*ln(137t/27t) = 5.5km/s.

Given the 2.5km/s required to reach GTO from LEO, that means that the upper stage has already provided 3km/s of delta-v already by the time the stack reaches LEO.

What is the LEO velocity? Given the standard gravitational parameter of the Earth mu = 3.986E14m^3/s^2 and we’ll pick an altitude of 150km, LEO is:
sqrt(3.986E14m^3/(s^2*(r_Earth+150km))) = 7814m/s.

But we’re concerned with the speed with respect to the ground, so we have to minus the contribution from the Earth’s rotation. Given 28 degrees lattitude (I think it’s actually launching from Boca Chica, but hey), that’s:
cos(28 degrees)*2*pi*r_Earth/day = a bit more than 400m/s.

So the relative speed is around 7.4km/s, let’s round to 7.5km/s.

So by the time the upper stage has been burning through 3km/s, the stack is at 7.5km/s velocity with respect to the ground. 3km/s less than that is 4.5km/s (minus a small amount of gravity loss, which is small by the time you’re at the upper stage).

So the core stage for the expendable Falcon Heavy is going at 4.5km/s relative to the atmosphere at stage sep from the upper stage.

With the reusable variants, the upper stage will be pushing a lighter load, so the upper stage has a higher delta-v and will be doing more of the work, and so the staging velocity (relative to the atmosphere) will be even less. So we’re talking about 4.5km/s, worst case. For a 15 ton payload to 1800m/s to go, you’re talking about ~3.6km/s staging velocity. That’s a much easier reentry problem than the 6km/s I’ve seen bandied about, and it could even be handled largely by propulsion.

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Fundamental cost of putting stuff in orbit: theoretical minimum vs RLV

What is the minimum energy of orbit, and how does that compare to the energy in a chemical rocket’s propellant?

Accessing a 150km LEO orbit requires first the energy to get to 150km. That’s roughly (in Energy/mass, or J/kg, aka m^2/s^2, the unit I’ll mostly use here): 150km*9.8m/s^2.

Orbital velocity at 150 km altitude is just v=sqrt(mu/a), where the distance from the center of the Earth a = r_Earth + 150km. Mu is the “standard gravitational parameter” of Earth, or ~3.986*10^14 m^3/s^2.

(BTW, I’ll write numbers like 3.986*10^14 in a more compact notation: 3.986E14.)

So v= sqrt(3.986E14m^3/s^2/(r_Earth+150km)) = 7814m/s ( here is the google calculation: https://www.google.com/webhp?q=sqrt(3.986E14m^3/s^2/(r_Earth%2B150km)) ).

But we can minus the speed from the rotation of the Earth: v= sqrt(3.986E14m^3/s^2/(r_Earth+150km)) – 2*pi*r_Earth/day

Now we need to make this in terms of energy in order to add that potential energy from being 150km high:
E_specific (energy/mass) = .5*(sqrt(3.986E14m^3/s^2/(r_Earth+150km)) – 2*pi*r_Earth/day) + 150km*9.8m/s^2

Which is roughly: 28,480,000 m^2/s^2 or 28.5MJ/kg. That’s 7.9kWh/kg or just under $1 per kg to LEO at typical 10-12 cents per kWh.
And in terms of delta-v, it’s: v = sqrt(2*E) = 7550m/s or so.

That’s zero aero or gravity drag, launching due East on the equator. Imagine a 150km tall tower with a 100% efficient electromagnetic launch mechanism on the top, including the energy required to lift stuff up that tower and assuming no energy loss from the sled, no mass for the encapsulating of the payload, and 100% efficiency for electromagnetic launch. None of these are realistic assumptions.

Let’s compare with chemical launch. Assume a hypothetical stoichiometric methane/oxygen rocket engine operating at 3.7km/s exhaust velocity. This is very aggressive (especially at sea level), would probably melt the engine due to operating stoichiometrically, but it may actually be possible.

A stoich methane/oxygen mix, with methane having 55.5MJ/kg specific energy and the mix having 11.1MJ/kg, would have a theoretical exhaust velocity, if you totally convert chemical energy to jet energy, of 4.712km/s, so 3.7km/s isn’t physically impossible in the least (would be feasible in vacuum, but would require incredibly high pressures at sea level).
Anyway, let’s assume a mass ratio of, say, 25 for each stage. Let’s assume a 100 ton payload. The first stage weighs 120 tons dry (25 times that wet), and the next stage 10 tons dry (etc). That gets us 9km/s delta-v, which we’ll say is good enough, launching on the equator due East to 150km altitude.

Work: 3.7*ln((25*120+(25*10+100))/((25*10+100)+120)+3.7*ln((25*10+100)/(100+10)

We assume the dry mass magically can be recovered at no mass penalty (I will address this in another post…).

Mass of the propellant is: 120*24 + 10*24 = 3120 tons. Or 31.2 kg of propellant per kg to orbit. At 11.1MJ/kg, that’s 346MJ/kg of chemical energy in the form of methane. Natural gas is about $0.30 per therm in bulk. A therm is about 105MJ. So the cost of chemical energy to put stuff in orbit via chemical rocket like I described is actually ALSO $1/kg, and with arguably more realistic (though also aggressive) assumptions.

Moral of the story: It’s not, and never ever has been, about the cost of energy to get to orbit. Such arguments are flawed.

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SpaceX Amateur Business Case Study

There have been several times in recent weeks that people either in person or on the internet have speculated about SpaceX’s finances and business model. In some cases the speculations have been that SpaceX is pricing their Falcon 9 below cost to try and drive ULA and other competitors out of business. I’ve seen other analyses on the pro-SpaceX side that seem to think that $6M F9R flights to orbit are right around the corner. I finally got curious enough that I wanted to run some of my own numbers using publicly available information to see what I could learn. I was a bit worried at first that if my analysis didn’t come out looking anything short of amazing for SpaceX that I’d get burned at the stake as a heretic, but I decided to publish this analysis anyway, including my spreadsheet I came up with so others can play with it and draw their own conclusions. Also, to save space I’m going to put all my disclaimers into this footnote1.

The four main questions I wanted to try to answer were:

  1. How realistic/sustainable is the current $61.2M price for an expendable Falcon 9?
  2. How realistic is their goal of $40M for a partially-reusable Falcon 9?
  3. How realistic is their goal of eventual $6-7M Falcon 9 flights if they could recover/reuse both stages?
  4. How much has SpaceX had to rely on spending pre-payments from future launches?

This was a fairly brief, 3hr exercise, so consider at best a really, really crude SWAG, but I gained some interesting insights I had never noticed before. Before I get into answering my two questions, and discussing those interesting insights, I’d like to first discuss the methodology I used, and provide a copy of the spreadsheet in case you want to start poking around.

Methodology
The point of this exercise wasn’t to create a precise cashflow history of SpaceX, but to create a simplified model that could give some insights into some of the questions I previously mentioned. I wanted to stick with publicly available sources, and wanted to keep things simple and high-level. So I gathered key pieces of data including headcount at various times, list prices for their vehicles, timing of launches, and data on the value of government development contracts they’ve received 2. I then made several core cost assumptions:

  • I assumed that each employee cost SpaceX an average of $150k/yr burdened. This is lower than the traditional $200-250k/yr number you hear for bigger industry player, but is consistent with numbers I’ve seen for aerospace startup companies. This number includes not just direct salary, but also employment taxes, unemployment insurance/worker’s comp, fringe benefits (health insurance and other benefits), and other direct costs of employing people (computers, software seats3, etc). I had originally gone for $120k/yr for this number, but found that the numbers jibed better with historical data points we had if I used the higher $150k/person/yr number.
  • I assumed that “overhead” cost 50% of the direct labor costs. Overhead normally includes the salaries of non-engineering labor (executive, marketing, business, etc), but since I’ve just used a lump rate based on the headcount, this overhead number just includes facilities, infrastructure, tools and machinery, and R&D costs that weren’t for producing flight hardware. So Merlin test engines that didn’t fly would fit under this. As would the pads, the factories, the drone ships, Grasshopper, any Raptor development, etc. This is ridiculously high-level, but it would take a lot of work to get anything more precise. But this seems pretty reasonable since the labor cost included fringe benefits, and all of the indirect labor.
  • I assumed that on average for Falcon 1, Falcon 9, and Dragon, that the non-labor cost of goods sold was 25% of the item’s list price. Ie, if SpaceX says an expendable Falcon 9 costs $60M, I assumed that non-labor COGS was ~$15M. This covers raw materials, consumables, range fees, shipping costs, non-labor marginal testing costs, and all the components and sub-assemblies SpaceX still purchases for the launch4. This number was based on my assumption that SpaceX was probably targeting list prices that they expected to be able to make at least a 10% profit margin on, and that ~2/3 of the cost was labor and fixed costs. It was also based on my limited experience at Altius on space hardware  projects. The analysis didn’t seem wildly sensitive to this number, but it’s also one of the ones I’m least confident in.

I don’t think any of those are wildly controversial, though you can try fiddling with the numbers as you see fit using the spreadsheet I provided.

I then made some more or less dubious simplifying assumptions (many documented in comment boxes in the spreadsheet):

  • Instead of trying to figure out exactly when SpaceX got paid for what milestones for each contract, I typically took the contract value and duration, and evenly spread the value of the contract over the years in question. In reality payments may have been more lumpy, more front-loaded or more back-loaded. If someone really wants to take the time to dig through public records to try and time the payments more accurate, be my guest (and send me a copy of the updated spreadsheet and I’ll put it in an update).
  • I inflated the value of old contracts and revenues into 2016 dollars using Wolfram Alpha, to make costs and revenues easier to compare with 2016 numbers. I’m not sure what inflation calculator they used or if it’s one that is uncontroversial. I also realized that on the cost side I didn’t inflate the labor costs to 2016 dollars. So that may be an update worth doing down the road to be internally consistent. Non-labor COGS is inflated though because it’s based on the inflated list prices. Most importantly, I’m not 100% sure this was a useful way to do things. But that’s what I did.
  • For commercial Falcon 1 and Falcon 9 flights, I assumed the actual revenue for the flight was 10% above the list price on average for “added services.” As I’ve heard from some people who’ve spoken with SpaceX in the past, the list price covers a pretty basic service, and that many items people care about cost extra. One NASA mission (I can’t remember if it was Jason or DISCOVR) for instance was listed as costing $97M even though the list price was only ~$60M. I don’t think there’s anything wrong with this, but I wanted to account for it. Once again, if you disagree with my 10% estimate, feel free to tweak it up or down. I didn’t include this added service 10% for CRS flights, since I assumed those were baked into the price.
  • Probably the biggest and most explicitly incorrect assumption I made was that SpaceX only got paid for flights upon completion, and that all of the revenue (and non-labor COGS) for that flight happened in the year that the flight occured. In reality, in order to get a manifest slot you almost always have to pay a non-refundable deposit, and there are many milestones along the way, that typically front-load a lot of the cost of a launch so that by the time you get to the actual launch, you’ve already paid most of the money for the flight, with the actual flight itself only the last of several milestones. This is pretty common in industry as I understand it. The reasons I didn’t include some sort of modeling of prepayments was for a few reasons: a) I don’t think there’s enough public info to accurately time prepayments for commercial flights even if I wanted to, and b) one of the main questions I wanted to answer was how much SpaceX was using spending front-loaded pre-payments to finance cashflow. Fortunately, we should be able to estimate how much of the prepayment money they’ve spent based on the difference between cumulative revenues + investments – costs. Basically if they’ve spent more money than they have received from completed flights, R&D contracts, and investment, it seems like the only real place that money could come from would be spending pre-sales.
  • For CRS flights, I assumed that the Falcon 9 + Dragon cost $1.6B/12flts = $133M/flt in dollars of the year that the flight occurred. I assumed that the price of the Dragon and added services was this $133M number (inflated to $2016) minus the inflated Falcon 9 list price for that year.
  • I assumed SpaceX got paid list price even for flights that failed. My guess is this isn’t precisely true, but probably closeish.
  • For years when I didn’t have an explicit headcount, or one I could remember for the earliest years, I interpolated from years on either side.
  • For years leading up to the first Falcon 1 flights, I assumed that Elon invested money to counter any difference between the revenues and costs, since there weren’t many preorders they could take milestone money from to finance cashflow.
  • There was ~$100M of non-Elon investment in SpaceX from various groups like Founders Fund and DFJ in the 2008-2012 timeframe. We had timing of the 2008 money, but not for the remaining $80M, so I evenly distributed it (and inflated it to 2016 dollars).
  • I only went up through 2015 in the historical data, so I don’t include any revenues or data for Dragon V2 flights, Falcon Heavy flights, or reusable Falcon 9 flights in the historical section. Even in the what-if sections, I explicitly leave out Dragon V2 flights5 and Falcon Heavy flights to try and focus on the specific questions I wanted to answer, and to keep this model from rapidly ballooning into something too complex to get useful information out of.

So all told, this is a flawed, but hopefully useful model. And one you can tweak to your hearts content to see if you come to different conclusions than I.

How Well Does the Model Do?
We don’t have a lot of data points to compare with, but there are two data points worth looking at:

  1. The model suggests that not counting DARPA and USAF contract R&D money, Elon had to put in ~$103M of his own money to get Falcon 1 to the point where it was flying. That’s around $85M in then-year dollars, so in the right ballpark for the ~$90M Falcon I development budget you hear quoted. It’s not perfect, but close enough to suggest we’re in the general ballpark.
  2. The cumulative cost through the first flights of Falcon 9/Dragon in 2010 are estimated at ~$800M inflated. The canonical number was $390M for Falcon 1 + Falcon 9v1.0 development, which would imply that Dragon was around $350M or so once you separated out operational costs and such. This also seems close-ish.

I’m sure that with more time and a more granular approach you could probably get the numbers closer, but this suggests we have a model that’s at least in the right ballpark.

Answers to The Four Questions
So, if you assume that my model isn’t entirely useless, we can now take a look at my three questions from earlier. This is what the “what if” columns on the right are for. The short version is that I think:

  1. While I think you can make the case that SpaceX isn’t yet to a flightrate where they are making profit at the current $61.2M list price, my model suggests they’d only need ~13 Falcon 9 flights with 3 of those being CRS flights in 2016 in order to breakeven at that price point. With the amount of people and infrastructure they have, 13 flights per year (with 3 being CRS flights) doesn’t seem unreasonable, even if they don’t make it all the way there this year. So this confirms my intuition that their $61.2M number for Falcon 9 isn’t so much them trying to sell at a loss to push out their competitors, but more them not having reached the flight rate that they’re theoretically capable of with their current team and infrastructure.
  2. Based on this model, I also don’t think getting down to $40M/yr for a semi-reusable Falcon 9 is totally unrealistic. There’s a lot of squishiness in my model about how I account for reusability, but it seems like we’re probably only talking about ~15-18 flights with ~3 of those being Dragon flights in order to make that at least somewhat realistic, assuming the downsize to ~4000 people after the commercial crew development is over. Which seems doable. If they keep their full 6000 people, they’d need nearly 30 flights per year to break even at $40M/flt, which seems optimistically high, but I don’t think they need the full 6000 people once the commercial crew development and certification is completed. This more or less confirms my intuition that a modest price decrease with reuse seems realistic.
  3. Dramatic drops in price seem pretty optimistic though. Even if you assume that the non-labor COGS drops by 90% per flight with reuse, and that they can get back down to 2500 people to service everything, it still seems like you’d need >50 flts per year to make those prices work, and I don’t consider that remotely realistic yet with the current market. If they kept their current team size, they’d need over 100-150 flights per year to make the $7M/flt number work… I don’t think that’s likely to happen. That said, even a 30% drop from their current prices is pretty amazing.
  4. There does seem to be some merit to the belief that SpaceX has been living off of prepayments. If you ignore the $1B fidelity investment last year (ie assume that it was set aside explicitly for the satellite business, and not used to finance cashflow), SpaceX has currently spent around ~$1.2B of prepayments (down a little from a high of around ~$1.3B in 2014). If you assume that they priced Falcon 9 with only a modest 10% profit margin6, that means that around $1B of that prepayment money that they’ve already spent is money they’ll need to carry out the missions on their manifest. With ~40ish flights on their manifest, they have a backlog worth ~$3B, so that represents a lot of their backlog that they’ve already spent. They’ve probably done some of the work for those flights, but does anyone really think they’ve done ~1/3 of the work needed for those 40 flights? Probably not. That said, is this some fatal problem? Probably not. The Google/Fidelity investment is about the same size as this amount, so even if something were to happen they’re probably safe now. And with the commercial crew contracts, they actually had more completed revenue than costs, and that’s likely going to get better this year if they can get their flight rate up. Lastly, so long as their manifest continues to either grow or at least stay steady, that will also help with cashflow. Unless they have another launch failure and 6 month standdown within the next year or two, I think they’re probably safe. Or at least as safe as any other commercial operator in this industry.

Other Observations

There were also several other interesting observations that stuck out to me:

    SpaceX has only recently reached the point where their revenue from actual flights has surpassed their revenue from DARPA and NASA R&D contracts. They’re currently at $1.7B from flights vs $1.5B for R&D contracts. And most of their flight revenue to-date has come from CRS missions.But while SpaceX has benefited a lot from their public-private partnership with NASA, it looks like over the next several years more and more of their business will be coming from commercial and non-NASA customers.A lot of their current team-size is likely driven not by Falcon 9 and Dragon fabrication and flight operations, but development work for Commercial Crew. With how NASA chose to run the Commercial Crew program, more as a traditional contract development with deep NASA oversight, maybe this isn’t that surprising.If SpaceX suffers another launch failure in the next 1-2 years, I think they could probably survive as a company, but expect that would significantly delay their ability to field their LEO commsat constellation–ie they’d have to spend a lot of that Fidelity/Google investment to cover cashflow while they work through the return to flight.I wouldn’t be surprised if SpaceX downsized after commercial crew certification is over. It would make achieving their cost targets more realistic, and they probably won’t need as big of a production staff if reuse really pans out in the way they expect.Based on my model’s prediction of their cost structure, and how much of their prepayments they’ve already eaten through, I’m skeptical that they’re moving anywhere near as fast with Raptor and MCT as most of their fans seem to think they are.

Conclusions
All told, I think this was an interesting exercise, even if it turns out that some of my assumptions were off by a bit. My big takeaways are that SpaceX’s current price numbers seem realistic, and their $40M price target with reuse is also probably also achievable eventually. Their financial situation seems less precarious now than it has been at any point in their history, though even one more launch failure anytime soon would hurt quite a bit. I also really don’t think they have a clear path forward to the more optimistic numbers they’ve thrown out, even with full stage reuse, but $40M for a Falcon 9 is still pretty amazing. I genuinely hope ULA and/or Blue Origin can continue to step up their game enough to stay competitive with SpaceX–it would be awesome to have two or three US providers able to launch rockets reliably at those kind of prices–that would go a long way towards enabling the kind of space future we’d all like to see.

Anyhow, go nuts with the spreadsheet, and if anyone has a ton of time on their hands and wants to try and time the revenue and estimate prepayments and all that better than I have, I’d be interested in seeing what you come up with, and may even post the results if they’re interesting enough.

[Update 1: A commenter pointed out that this site (https://www.sec.gov/cgi-bin/browse-edgar?company=space+exploration+technologies&owner=exclude&action=getcompany) provides data on the timing and size of previous SpaceX investment rounds. Between this and government data on contract payment timing, we could probably increase the fidelity of the spreadsheet by quite a bit. If anyone wants to do that, let me know. If not I’ll see if I can find the time to do that in the coming days.

Also, while this impacts revenue going forward, not historical revenue, SpaceX did win a contract for matching funds from the USAF for upper stage engine development. This will help lower the number of flights they would need to break even by at least one or two. Continuing to win big government development contracts like this will help SpaceX going forward.]

Posted in Business, Commercial Crew, Commercial Space, COTS, Launch Vehicles, SpaceX | 44 Comments

Lunar Orbital Facility Location Options

For travel throughout cislunar space, I’ve long been an advocate of having depots on both ends of the journey. The LEO depot provides a refueling stop at the first practical point after leaving the ground, and also a spot for bringing vehicles back from lunar space for refueling for their next trip out. The lunar orbit depot plays a similar role for flights to/from the lunar surface, as well potentially, as being a staging location for departures into interplanetary space. By launching from a lunar facility near the top of earth’s gravity well, it’s both possible to use low-thrust trajectories in and out of cislunar space, as well as to do an earth swingby with a departure burn at apogee for high-thrust departures taking maximum advantage of the Oberth effect.

One important question however has been where to place the lunar orbital facility.

Lunar Orbital Facility Orbit Options
A recent FISO telecon presentation by Ryan Whitley and Roland Martinez of NASA JSC describes and discusses several of these staging orbit options. I’ll be reposting snapshots of a few of their slides to introduce the orbits, but here you can find their full presentation:

http://spirit.as.utexas.edu/%7Efiso/telecon/Whitley_4-13-16/Whitley_4-13-16.pdf

They discuss most of the commonly cited options including Low Lunar Orbit, Frozen Orbits, L2 Halo Orbits, Distant Retrograde Orbits, and a more recently discovered option, Near Rectilinear Orbits.

This slide shows some of the smaller lunar orbit options and descriptions:

SmallerCislunarOrbitsAnd this slide shows some of the larger lunar orbit options, with descriptions:

LargerCislunarOrbits

And this slide shows all of the orbits relative to each other to give you a better idea of what they look like:

AllLunarOrbitsSummary

Comparison of Options
While Whitley and Martinez in their FISO telecon focus on evaluating the various staging orbits from the standpoint of NASA missions using the Orion capsule, they still provide a lot of useful information for evaluating options for the location of a lunar orbital facility/depot. To me, some of the considerations for locating a lunar orbital facility are:

  • How frequently do you have opportunities to travel from a LEO facility to the lunar facility, and how frequently you can travel the other direction?1
  • How much delta-V does it take to go between the facility and LEO and the facility and the lunar surface?
  • How long is the transit between the location and the lunar surface?
  • How useful is the orbit for supporting deep space missions?
  • How hard is it to reach various lunar surface destinations from the lunar orbital facility location?
  • What is the thermal environment like in the orbit?
  • And how much of the lunar surface to destination delta-V can be provided by some sort of propellantless lunar launch scheme2?

Based on these considerations, I’d like to focus the rest of this post on the pros and cons of the two options I consider most interesting–L2 Halo Orbits and Near Rectilinear Orbits.

Pros and Cons of EML-2 Halo Orbits
EML-2 orbits have been my favorite option ever since learning about the low delta-V cost of reaching them via powered lunar swingbys. They have a lot going for them, including:

  • One of the lowest delta-V stopping points in the lunar vicinity, requiring only ~3.43km/s of delta-V from LEO.
  • Easy access to/from a LEO facility on every LEO-lunar or lunar-LEO window.
  • Any-time access to/from anywhere on the lunar surface.
  • Low stationkeeping delta-V3
  • Benign and cold thermal environment4
  • Continuous communications with Earth, and most of the farside of the Moon.
  • Good staging point for both deep-space and lunar missions.
  • Could become a starting location for a lunar space elevator.

But EML-2 does have a few drawbacks:

  • Long LEO-EML2 and EML2-LEO transit times5 for the low delta-V powered-swingby option.
  • Long EML2 to lunar surface (and vice versa) travel times6
  • It wasn’t clear that a propellantless lunar launch option located at either pole could launch easily to EML2. An elliptical orbit from such a launcher would have its line of apsides pass through the launch location, which would be orthogonal to the Moon-EML2 line. You could launch into a polar LLO, and then do multiple burns from there to EML2, but the propellantless launch option would only provide the first leg of the trip (surface to LLO).

The long trip times mean that the vehicles taking people between LEO and EML2 and between EML2 and the Moon will require much more extensive life support and accommodations than would be needed if the trip were shorter. That will drive up the dry mass of those systems, and by extension the propellant and overall cost of moving people to and from EML2.

Pros, Cons, and Questions Regarding Near Rectilinear Orbits
Starting several months ago, some of my astrogator friends started telling me about NASA’s interest in Near Rectilinear Orbits for exploration missions. After all the talk about Distant Retrograde Orbits, this sounded a bit like the “flavor of the week” syndrome, but the FISO presentation helps explain some of the allure of such orbits:

  • Only slightly higher delta-V to/from LEO to NROs compared to LEO to EML27.
  • Because the NRO orbit’s perilune is only 2000km from the Moon’s surface, once per 6-8 day orbit, the orbit lines up so that the travel time between NROs and the lunar surface drops to 0.5 days.
  • Powered swingby trajectories between LEO and NROs take approximately 5 days each direction, instead of 9-11 for EML2.
  • Slight lower delta-V between NROs and the lunar surface compared to EML2.
  • The NRO is close enough to an elliptical polar orbit that it might be possible for a polar base to use propellantless launch techniques to fling payloads nearly into NRO, with possibly only minor adjustments and raising the perilune with a burn near apolune half an orbit later8

The benefits of shorter transit times are pretty important, but there are still a couple of relative drawbacks and open questions:

  • While it’s possible to get from LEO to a given NRO orbit during every lunar injection window, the NRO facility will be at different points in its orbit during each window, which may make a first-orbit rendezvous either infeasible or it might cost additional delta-V. I’d want to get this resolved, because while this isn’t an issue for one-off, ground-launched missions like the NASA folks were thinking of, this would be a real issue for reusable spaceship flights between a LEO and NRO facility.
  • Likewise, departures from the NRO may not be in the optimal part of the orbit for the Earth return maneuver when the timing is right to return to the plane of the LEO facility. This isn’t a problem if you’re doing a direct return, but once again is a big pain in the neck for reuse of space hardware. Once again this is something I’d want to analyze more before settling on an NRO orbit.
  • Additionally, the NRO facility has LOS with one lunar pole about 86% of the time (while heading out and coming back from apolune), but only sees the other facility for a brief period near perilune. If you’re planning on using propellantless launch methods to send stuff from a polar lunar settlement to the NRO facility, it’s going to be in an NRO with apilune on the opposite side of the moon from your lunar settlement, meaning you’ll only be in contact briefly for maybe 1 day out of a week.
  • Because the perilune is only 2000km, the heating environment is going to be warmer than EML2, with slightly higher boiloff, but this is probably only a minor difference–it should still be tons easier to keep cryo boiloff low in an NRO than in LEO.

Conclusions?
While NRO orbits have some really interesting characteristics, I’d really want answers to those first two concerns before I’d pick it for the location of a lunar orbital facility. If you can’t get to it on a regular basis from a given LEO depot without having to do complicated trajectories, or paying big penalties in flight duration or delta-V, then that would likely outweigh the benefits. If on the other hand, it’s not a big deal to adjust the trajectory on the way to and from the NRO facility to enable rendezvous with the facility regardless of where it is within its orbit when the LEO to lunar launch window opens, then it could be a really interesting location for a lunar transportation node. I’ll have to see if I can get some of my astrogator friends to weigh in on those questions. Until then I’m probably still more of a fan of EML-2, in spite of the annoyingly long transit times.

[Update 1: After speaking with an astrogator friend who’s been looking at NROs to support lunar missions, he thinks it might be possible to put an NRO facility in an orbit whose period is synchronized with the average time between launch windows from the LEO facility. If that works, that would mean the NRO facility would be in approximately the same part of its orbit during each trip to/from the Earth. There are questions of if you can make an NRO orbit with a long enough period (~9 days) to make that work, and if the NRO facility could be made to line up both for arrivals and departures from/to Earth, but hopefully he’ll have more opportunity to dig into that further later this year.]

Posted in Lunar Exploration and Development, Propellant Depots, Space Development, Space Transportation | 15 Comments

New (?) ideas for utilizing space for business: hypergravity for athletic training

(Note, I had previously written this along with the isotope separation, but wanted to give that idea a chance for discussion first.)

Another possible use for hypergravity is for training humans.

A big 2-gee facility on Earth would be expensive to build and maintain and would necessarily be small enough that you’d get large Coriolis effects. You’d be limited in size. But in orbit, you could build a large training facility that top athletes could train in, much like athletes train at high altitude. The athletes would develop denser bones, stronger muscles, and you could also reduce the oxygen concentration to get the benefits of high altitude training for lung capacity, etc. Soldiers, especially special forces, could train for months in such a facility as well.

Considering that the top 100 athletes make over $3.2 billion per year, you’ve got to think about the next 101-200 top athletes… Would they be willing to invest, say, $1-2 million so they could get in the top 100? If this proves to be a decisive advantage and is cheap enough (say $50,000 per person per week?), you could have entire teams training in large equatorial LEO (where the radiation levels are quite low, with shielding for the rest) rotating hypergravity training facilities which could also serve as orbital hotels at the lower gravity levels.

And what is a few hundred (or even thousand) supersoldiers worth per soldier? (I leave aside the idea of using the station as launch-point for special forces soldiers… There are plenty of military applications of space already.)

Each market could be multiple billion per year, and it’d intrinsically involve a real advantage to human spaceflight.

Another thing: Space tourism and settlement and even the NASA astronaut corp are for space nuts. This is one of the very few reasons why non-space-nuts would want to fly in orbit (for more than just point-to-point), and it could potentially be tens of thousands of people (athletes, soldiers, fitness nuts) in very large facilities. It’s not just because “space is neat.”

Posted in Uncategorized | 12 Comments

How Relevant is New Shepard to Orbital Launch?

With Blue Origin’s successful launches and recoveries of New Shepard starting just about six months ago, there have been many people questioning how relevant it is to future orbital launch vehicles. Some of this seems to be honest curiosity about how much more Blue Origin needs to learn before it can join SpaceX, ULA, and OrbitalATK in having an orbit-capable launch vehicle, and some quite frankly seems to be unsportsmanlike attempts by SpaceX fans trying to downplay Blue Origin’s reusable launch accomplishments1. Regardless of the motives of the question though, it’s still a legitimate and interesting technical question, and one worth discussing. A lot of what I’m about to discuss is a rehash of an article I wrote almost a decade ago2 about sRLV performance requirements that seems to have been forgotten by many of those discussing these issues.

How Much Delta-V does an Existing New Shepard Produce?
A lot of the discussion I’ve seen about the question of New Shepard’s relevance to orbital launch is based on what I think are erroneous assumptions about the Delta-V capability of the New Shephard vehicle, based on naive analysis. You’ve probably read at least one article where someone stated something along the lines of “While their New Shepard landing was really neat, orbital launch requires X times more energy than suborbital launch”, where X is usually a large number between 25 and 81. The problem is that most of this math is really, really naive.

Most people who haven’t worked with rockets, but who know physics, will use kinetic energy vs. potential energy to solve for the required rocket velocity to reach 100km. 1/2mv^2 = mgh, m’s cancel out, and you solve for v and get ~1400m/s. If you compare this to the velocity needed for orbit (~7800m/s horizontal velocity), that works out to 5.5x more velocity and 31x more energy to reach orbit. The problem is that 1400m/s isn’t the delta-V capacity of New Shepard, and in fact if the New Shepard only had 1400m/s of delta-V capacity, it would have a hard time getting to 25km altitude, let alone 100km.

Why is that? Landing propulsion, drag losses, and gravity losses3. These are due to earth having an atmosphere, propulsion systems having non-infinite thrust to weight ratio, and needing to slow down so your rocket doesn’t go splat.

So let’s take a look at each of these in turn (in order of ease of estimating them):

  • Gravity Losses: This is the easiest term to calculate, because New Shepard flies vertically. Every second that the engine is firing straight down, you’re losing 9.807m/s of delta-V to gravity losses. According to Wikipedia, the ascent burn is ~110s, and based on the video of the most recent landing, I counted approximately 17s of landing burn, yielding a total gravity loss of ~1245m/s.
  • Landing Losses: The next easiest to estimate is the landing losses. I’m just going to go off of a comment Blue Origin made that if the engine ignition at 3600ft had failed, that six seconds later, the stage would’ve hit the ground. I’m going to assume that 3600ft is engine start altitude, and that startup takes 2 seconds, so that the landing velocity that has to be killed is 3600ft/8s converted to metric (~137m/s). I’m sure you could get a higher fidelity number by some other means, but this is just an estimate.
  • Drag Losses: The hardest to estimate is the drag losses. Usually to do this right, you’d want to create a numerical simulation of the whole flight with drag force varying by velocity and altitude, engine thrust and Isp varying with altitude, and the vehicle mass changing as propellant is consumed. You can do a reasonable hack at a 1DOF flight analysis using Excel, if you have enough information, but a lot of the information is guesswork anyway, so I took a shortcut hack. I found an online reference to drag estimates for historical launch vehicles. I took the two vehicles from the list without strapons (Atlas I and Saturn V), and extrapolated the drag loss delta-V by assuming it scaled linearly with frontal area and inversely with liftoff mass. This should make sense because the drag force is linearly proportional to frontal area4, and the drag acceleration is inversely proportional to the mass5. The drag loss delta-V is really just the integral of the drag acceleration with respect to time. Using a 3.66m frontal diameter for New Shepard, and a ~80klb takeoff weight, I’m getting ~528m/s of drag losses. That number is probably only accurate to with in +/- 25% due to all the simplifying assumptions we made, but without doing a full-blown trajectory analysis that’s about the best we can do at the moment. Note this is 4-5x the drag losses of a typical orbital launch in large part due to the very low ballistic coefficient6 of New Shepard compared to an orbital vehicle7. New Shepard has almost the same frontal area of a Falcon 9/Dragon launch while having a takeoff mass almost 15x lower.

If you take those numbers and add them to the ~1400m/s we had just to provide the required potential energy increase, you get a total New Shepard stage delta-V of ~3300m/s8. And that 3300m/s is with a 8000lb capsule as the payload on top. Compared to the ~9000m/s a typical launch vehicle needs to make orbit heading due east, once you’ve included gravity and drag losses, and that doesn’t sound quite so shabby anymore. For orbit you still need 7.4x more energy, but that doesn’t sound anywhere near as cool as 25-81x.

New Shepard Derived Upper Stage
Two other considerations are important when thinking about developing an expendable upper stage based on the New Shepard vehicle: New Shepard does not use a vacuum optimized engine, and New Shepard carries a lot of mass in its reuse hardware.

Because New Shepard is a single-engine vehicle that does powered landing, the engine has to be able to stably throttle down to ~20% of it’s liftoff thrust. This implies that the engine has a very low expansion ratio compared to an upper stage. My best estimates I’ve seen for BE-3 performance is actually only a bit better than the RD-180 Isp-wise: 310s SL and 360s Vac. Which interesting is really similar to the performance of the RL-10A-5 engines that were made for the DC-X, which also had to do low-altitude hover and land. The BE-3U upper stage engine that you would use on an expendable orbital upper stage however, will have a much higher expansion ratio, because you don’t need to do low-altitude, low-thrust operations. I haven’t seen great estimates for the BE-3U engine performance yet, but my guess is probably in the 440s range, possibly higher. Lower than RL-10 because of not being a closed-cycle engine, but dramatically better than the vacuum and mission-averaged Isp you’d see on BE-3 used suborbitally. If you assume that the dry mass of the New Shepard stage is ~30klb plus the 8klb payload9, swapping in the BE-3U for the BE-3, and operating purely in vacuum gets the stage up to ~4100m/s delta-V, which would require a first stage staging Mach Number of ~10.8, which IIRC is only a bit higher than the staging velocity used by F9R with barge landings.

If you assume the reuse hardware (the steering fins on top and bottom, the landing legs and hydraulics, etc) are 30% of the stage dry mass, getting rid of those and going with the BE-3U upper stage engine gets the stage up to ~4840m/s, which would require the first stage to stage at around Mach 8.6. If you assume the reuse hardware is 40% of the stage dry weight, you get ~5160m/s, requiring a Mach 7.7 staging velocity. Both of which are right around the high end of the range for what you could achieve with a ground boost-back recovered first stage.

And all of that is without stretching the tanks any to take advantage of the much higher vacuum thrust of a BE-3U, or the much lower needed T/W ratio for an upper stage (this stage would have a 2:1 T/W ratio instead of the ~1:3 T/W ratio on the last Centaur flight).

Long-story short, it looks like New Shepard is very relevant for becoming the expendable upper stage of a TSTO RLV, just like Blue Origin has been saying.

[Update 1: I ran the numbers, and with the same pmf as the existing New Shepard sans reuse equipment (80%), and same 8000lb payload, but with tanks scaled up to have the stage T/W ratio close to 1:1, the upper stage would have ~5200-5600m/s of delta-V, requiring a staging velocity of only Mach 6.4-7.6, which is just above the sweet spot for a boostback RTLS first stage.]

[Update 2: Chris pointed out that my description of gravity losses was a bit of an oversimplification that overcounts the gravity loss effects a bit, and that the landing dV (~300m/s including gravity losses) was with just the stage and not the capsule, thus knocking ~80m/s off of my estimate. Also, the numbers from the FAA Experimental permit were a little different from what was reported in the first version of this post–I thought the 30klb dry mass included the capsule, but it didn’t include it. I’ve updated the numbers throughout to reflect that. Now those FAA numbers are conservative numbers from their filing almost 2yrs before the first flight, but it does give us bounding numbers to work with. With those more conservative numbers, a New Shepard stage minus reuse hardware and with a BE-3U is still right in the range needed for an expendable upper stage for an 8000lb payload. Could they still improve their mass fraction or stretch their tanks to better take advantage of the higher thrust of the BE-3U? Of course, and I expect they will, but my point was that they’ve already demonstrated good-enough-for-orbital-launch performance.]

Posted in Blue Origin, Launch Vehicles | 18 Comments

New (?) ideas for utilizing space for business: hypergravity for isotopic enrichment

One night, as I was putting my daughter to bed and waiting for her to fall asleep, I tried to think of some new markets for space utilization.

We often hear about attempts to find industrial uses for microgravity for growing crystals, for purification of electronic materials (which is an actual thing with ACME Advanced Materials: http://www.a2-m.com/ ), maybe growth of certain metal foams, etc. However, in space, you’re in both a hard vacuum and not physically resting on anything, so you can spin up something, and it will simply keep on spinning (stably, if you spin it around the correct axis) nearly indefinitely without any additional energy input and no wear on bearings or anything. So in fact, you can get basically any gravity level you want, including HYPERgravity, nearly for free.

What are the applications of this?

The most obvious one I can think of that has the biggest market potential is isotopic enrichment of Uranium-235 for nuclear fission fuel. The world demand for electricity is about 10^20 Joules electric, and the price of Uranium fuel is about half a cent per kWh. About 40% of that is the cost of separation, with a Separative Work Unit costing around $100. So enrichment cost about 5*10^-10 dollars per Joule of electricity. That gives a world market for up to $50 billion for separation if we used just nuclear. If 10% of our market is nuclear, then $5 billion. Given 10^14J/kg of fissionable fuel and cost of 5*10^-10 $/J, then you have $50,000/kg of Uranium. Knock that down to 20% due to thermal to electrical conversion (power plants are usually better than that), and we’re at $10,000/kg. If you can get launch costs down to $50/kg, then it might be worth doing this (because you’re launching natural isotope ratios of Uranium to make the math easier). But interestingly, near-pure U235 is something that probably WOULD be economically worthwhile to export from Mars or Moon or asteroids (processed in orbit).

One can imagine other uses for isotopic separation, like lithium-6-enriched metal alloys. Lithium 6 is about 15% lighter than natural lithium. The best conductivity-to-mass-ratio wires (other than superconducting or microscopic graphene or nanotubes, etc) at room temperature is Lithium-6, nearly 4 times as good as copper. But that’s a much smaller market.

EDIT: I want to add some more realistic figures for cost, etc. There is currently perceived to be a glut of separation capacity, so the SWU price is still just $82 or so. But there’s also kind of a near-monopoly (quadropoly or something?) among separation providers, and the US is still using crappy gaseous diffusion plants which are super inefficient. So there may be a good argument for doing it anyway as a form of avoiding a sort of cartel arrangement. Also, since natural uranium is so poor in U235, it may actually make sense to pre-enrich the uranium before launch so that you don’t have to launch as much of it. Suppose we’re trying to make 95% U235-enriched Uranium (quite highly enriched) and want our “tails” to contain just 0.1% U235 (vs 0.7% naturally). We want to maximize the number of SWUs we do for a given launched mass. I’ve found that occurs at about 25%-U235 pre-enriched. 5.23 SWUs per kilogram of uranium. According to this calculator: http://www.wise-uranium.org/nfcue.html
(I could have used the full expression for SWUs and massaged it with calculus to give the actual maximum, but I’m getting lazy.)
Multiplying that by the cost per SWU (about $82), we get about $430 per kilogram. In other words, the market value of the work we can do separating that Uranium, if our orbital isotope enrichment goes well,
is about $430/kg. So we probably need launch prices to be down around $100-200/kg for this to really work. But that’s not unreasonable, and there’s also some value in having an independent capability to do this.
….Then again, the elephant in the room here is that we’re talking about launching tons of already-highly-enriched uranium (enough to make a crude fission bomb) and recovering VERY highly enriched uranium. Enriched so much that we’d better be careful about how much we have together at one time. Kind of goes without saying that there’d be political opposition to such a scheme! But still, it would be another space market.

(And I redid the numbers for more power-plant-grade 4.5% low enriched uranium given natural 0.711% feed and 0.1% tail… It’s about $119-worth-of-work/kg launched, so not actually as bad as I thought, and isn’t super highly enriched and so politically is more feasible, since you’re not just shipping bomb-grade material around.)

…and all this is pretty irrelevant if you start breeding your fuel from natural uranium and thorium, which probably makes sense in the long term.

Posted in Uncategorized | 15 Comments

ESIL-8 Elements of Lunar Commerce Presentation

I was invited to give a talk on lunar commerce at a Emerging Space Industry Leaders workshop last week hosted by ULA at their Centennial, Colorado campus, and put on by my friends at Advanced Space LLC and the FAA Center of Excellence for Commercial Space Transportation. This workshop was primarily attended by a group of CU Boulder students and young professionals from the area, along with a few folks from ULA, Advanced Space, and myself, and was discussing commercial opportunities leveraging lunar resources. When I mentioned on Twitter that I was going to be talking at the workshop, several people wanted to hear more about what I presented about, so I figured a blog post or two were in order. In this post I’ll provide my presentation and some notes to go with it, as a lot of the slides are mostly pictures that I spoke to. If I get time, I’ll follow-up with a few short blog posts about some of the new ideas I had either preparing for or participating in this workshop.

First here’s a pdf copy of presentation: ElementsOfACislunarEconomy_1Apr2016

Electrical Analogy of Commerce (slides 3-5):
I started with an electrical analogy to frame the conversation. When you hear people talking about lunar resources, it’s often put in terms of “What could we get from the moon that’s so valuable that it’s worth going all the way there to get it?” As I was thinking about this problem, I realized that historically most trade started out with only the most expensive of goods. In the middle ages, we went to China for silks, rare spices, things like that. Gold and spices were two of the main allures for exploring the Americas, and one of the main things that put California initially on the map for much of America was the gold rush. In a way it makes sense though. If transportation networks are immature, extremely expensive, and extremely dangerous, only the most expensive goods are going to be worth transporting. But over time as transportation networks mature and technology improves, the cost and hassle of moving goods around drops dramatically, and you now start seeing dramatic shifts in commerce. As the price of goods required to drive commerce drops the amount and value of commerce actually dramatically increases. China makes far more off of exporting clothing, Walmart goods, and electronic devices today than it ever did (even inflation adjusted) from exporting luxury goods like silks and spices in the middle ages, even though the average inflation-adjusted value of the average export has decreased dramatically.

My point with respect to lunar resources is that the cost of getting goods to and from the Moon, and shipped throughout cislunar space drops, the scope and value of cislunar commerce is going to skyrocket, and most of the money likely won’t come from shipping the most uber value-dense materials (propellants, PGMs, etc), even if that’s what most are focusing on today.

To segue into the next section, talking about elements I’ve identified that we need to drive down the cost of cislunar commerce, I pointed out that while historically the cost per round-trip ticket to the moon1 has always been in the $500M-1B range, what would happen if that price could be brought down to $20M like tickets to the ISS have been in the past? What about $10M or $1M? As the price of travel to and from the Moon, and throughout Cislunar space goes down, it becomes easier and easier to experiment with new businesses, and for things like tourism and other economic activities that are further removed from mining and resource extraction.

Lowering the Resistance to Cislunar Commerce (slides 6-15)
So how do we get down to the magic $1M/person round-trip ticket? I’m not sure I know entirely how to get there, but there are several elements that seem like they’re critical. In many cases these revolve around an idea a colleague told me about from Amazon’s business model–he called it “looking for zeros.” Basically the idea is can you find a trick that allows you to take a typically required expense column in your business model and zero it out? Amazon apparently found a clever way to zero out inventory holding costs for itself by having suppliers store goods in Amazon’s factories, but only buying them when the customer places an order2.

Here were some of the key ideas I brought up that could help drive the cost of cislunar commerce down to interesting levels:

    1. Reusable Earth-to-Orbit and In-Space Transportation (slide 7): This one is pretty obvious and may feel like flogging a dead horse, but has a few less obvious points worth mentioning. First, earth-to-orbit reusability can be a two-edge sword, because while lower launch costs can dramatically lower the cost of harvesting lunar and/or NEO resources, launch from earth surface is also the most direct competitor to lunar and NEO-derived resources. The closer you get to the source for a resource (Earth, Moon, or NEOs) the more competitive that source is going to be as the supplier. Lunar and NEO mining advocates often point out that extra-terrestrial resources look really good at existing launch prices, but the question will be how awesome they look as the prices come down. I’m not sure, but it’ll be a fun process to watch. Second, you really want both complete earth-to-orbit reuse and in-space reuse, not just one or the other. I bring this up in part because ULA talks about refueling and reusing ACES in-space but downplays recovering ACES to Earth for earth-to-orbit reuse. Refueling of upper stages does make a lot of sense and opens up some very interesting possibilities when you start moving reusable in-space assets around. But if a payload is being launched from Earth’s surface, like say a satellite, it’s already going to be attached to an upper stage, and in most cases it makes more sense to refuel that stage the payload is already attached to rather than transferring the payload to a previously launched stage. So over time you’re going to end up with a glut of stages on orbit if you don’t also figure out how to recover and reuse upper stages for Earth-to-Orbit launch. I could3 go on, but those two sub-points will suffice for now.
    2. Knowing How Much Gravity People Need (slide 8): I’ve flogged this topic many times on this blog, particularly in this thread, but you may be wondering what this has to do with lowering the cost of cislunar commerce. One of the observations made many years ago in a Microcosm-led study4 on lowering the cost of lunar settlement was that one of the biggest costs of human bases on the Moon is the assumption that you have to swap crews out every few months. Most baseline plans presented over the years have assumed stays of 3-6 months or less per crew rotation, in some ways analogous to the ISS. Having to pay the tax of shipping everyone home every three months adds up quickly, even if you’re getting the return fuel on the Moon. Being able to extend tours to 1-5year tours of duty would dramatically lower the transportation costs associated with building up a lunar base, and a key prerequisite to making that happen is going to be knowing if humans can adapt well enough to 1/6g for that to be safe. If you assumed lunar gravity was just as bad as microgravity, you’d have a hard time getting approvals for much more than 1yr tours of duty, even if you made the other changes Microcosm suggested. But if it turns out that 1/6g is much closer to 1g healthiness-wise, longer stays would be practical. Especially in early days when transportation costs are the highest, allowing initial crew to stay longer I think will be critical to lowering the cost of getting a permanent toehold on the Moon. Imagine what colonizing the west would’ve been like if you had to send all your pioneers back East every 3-6 months! There’s also an intriguing market I realized could come out of all of this, but that’s a blog post for another day.
    3. Depots/Distributed Launch (slide 9): This one I’ve also flogged a lot on this blog. But in addition to being a key enabler for lower-cost transportation, and for fully-reusable in-space vehicles, Distributed Launch and Depots will likely be a key market for lunar resources as well. And yes, those pictures are both original Altius artwork. If we had the kind of backing of a Bigelow or a SpaceX, we’d be primarily focused on bringing depots and distributed launch to market. As it is, we have to bootstrap and take a much longer, more circuitous route, but I wanted it to be clear that at least someone is trying to work this problem.
    4. Atmospheric Gathering (slide 10): Back when Bernard, Dallas, and I presented our propellant depot paper at AIAA SPACE 2009, the paper session we were in included a paper about orbital atmospheric gathering. The idea is to create a spacecraft that could fly in a lowish orbit, scoop-up some fraction of the particles it collides with, capture, compress, and sort those particles, and spit some of them out the back fast enough to overcome the drag. If you could make this crazy idea work, you could harvest atmospheric gases without having to launch them from Earth, potentially saving tons of money in the long-run. The idea has been around at least since the PROFAC concept was proposed 60yrs ago, though that concept required a nuclear reactor flying around at 100km altitude, which is a little bit too crazy even for me. I won’t go into the technical challenges for atmospheric gathering in this post, but I think I’ve finally hit on a solution to one of the hardest, so I’m starting to pay more attention to the concept. If such a technology can be made to work, it might be able to provide a cheaper source of at least LOX in low earth orbit, basically zeroing or nearly-zeroing out the cost of launching that LOX. Like RLVs, this is a two-edge sword, as this both lowers the cost of getting to/from the Moon, but would also compete with lunar propellants.
    5. Aerobraking/Aerocapture (slide 11): This is another hobby horse of mine, especially with the work we started doing supporting MSNW on their Magnetoshell Aerocapture technology development a few years ago. Zeroing out most of the propellant cost of braking into LEO is a huge cost savings for reusable in-space vehicles. If you want to reuse things in-space, you have to actually stop in orbit, not just letting most of the stuff burn up while your crew returns in a tiny capsule. And stopping in LEO on the way back from the Moon takes just as much delta-V as doing a trans-lunar injection in the first place. Doing this propulsively with LOX/LH2 cuts your payload from the Moon in half, doubling the cost/kg of propellant or materials delivered to LEO. If you can do this via aerocapture/aerobraking, especially with something that can do it in 1-2 passes, and doesn’t weigh a large fraction of your spacecraft dry mass, the cost of bringing stuff back from the Moon or elsewhere cuts in half almost immediately. It also leads to my next hobby horse: real spaceships.
    6. Real Spaceships (slide 12): While this has been in my mind for years, I don’t know if I’ve ever really gotten into this on Selenian Boondocks like I’ve wanted to. If you look at most space architectures over the past 50-60 years (outside of science fiction), they’ve always assumed that you carry a reentry capsule with you, and toss almost everything away along the way. I think the Apollo engineers called this the disintegrating totem pole approach. Even approaches that have used aerobraking/aerocapture have had to look like big reentry vehicles. But between solar electric propulsion and/or technologies like magnetoshell aerocapture, you may now be able to have vehicles that look nothing like an aerodynamic reentry shape that can shuttle repeatedly between Earth and other deep space destinations (the Moon, Mars, NEOs, Venus, etc). Some of these may be exploration vehicles, so may be passenger cyclers, so may be cargo haulers. But I think real spaceships are going to be an important part of lowering the cost of at least passenger travel throughout cislunar space. Right now reentry vehicles tend to have very high launched mass per person. But what if you could leave most of the long-duration life support and accommodations mass on a cycler instead of the vehicle you have to haul to/from earth orbit? What if your earth-to-orbit passenger launcher had people packed in more like an aircraft, then you transferred (via another aircraft-packing-density vehicle) to a cycler that had your train or ocean liner like accommodations for the several day trip out to the Moon. You could leave the most massive elements looping around in cycler orbits and only have to accelerate/decelerate5 much lighter transfer pods, zeroing out a lot of the costs inherent with moving people around. If you design the cyclers to be modular, you can build them up over time, starting with rather modest vehicles, and growing them bigger and bigger as flight demand increases. I should probably save more for future blog posts.
    7. In-Situ Resource Utilization (slide 13): You’re not going to get cislunar transportation costs low without using lunar resources for at least propellant. Enough said.
    8. Human/Robotic Teams (slide 14): While I don’t think anyone these days is dumb enough to suggest trying to setup a lunar base without using robots to help the people, there are plenty of people silly enough to suggest having robots do all of the work before the people get there. I’m still very skeptical of the ability of robots to affordably handle the complex tasks of setting up a lunar propellant mining, processing, and shipping operation without at least a few people there. And even if it is somehow possible, I’m skeptical that it’s going to be cheaper and faster than a mix of robots and people working together6. I just think that robots make crappy people and people make crappy robots. The optimal mix is likely going to be many robotic minions7 per person, but having at least a few mechanically/electrically inclined people and a well-stocked machine shop is going to make things go amazingly smoother than trying to do this with just robots, IMO.
    9. Propellantless Lunar Launch and/or Landing (slide 15): I still need to finish my “Slings and Arrows of Outrageous Lunar Transportation Schemes” series, but finding a way to find a zero with landing and/or launching objects from the lunar surface is going to be important in driving down cislunar transportation costs. While there are some great reusable-rocket lunar lander ideas out there, like the Masten/ULA XEUS vehicle, finding a way to eventually get around the rocket equation for getting stuff up and down at the Moon is going to be a must if the Moon wants to be competitive in the long-term. Right now two of the biggest advantages NEOs have over the Moon is that prospecting can theoretically be done using small, low-cost micro- and maybe even nanosatellites, and that return delta-V can often be a lot lower8. Finding a way to at least get raw materials off the Moon without using rockets can negate that second benefit. Finding ways to land things safely on the Moon without propellant can dramatically lower the cost of setting up infrastructure. Eventually getting to safe ways to land and launch people without using propellant is the real holy grail, and is probably required if you ever want to get round-trip ticket prices down to $1M or less. That’s all nice you may be saying, but is that even remotely possible? I think so. But more on that when I actually get back to that blog series.

Can all of those pieces working together really get the cost of a round-trip ticket below $20M? $10M? $1M? I’m not sure, but I think so. Hopefully over the next several years on Selenian Boondocks I can find more time to pursue these various threads in more detail9.

Lunar Resources (slides 16-17)
I won’t go into detail on every item on this slide, but do have a few points I tried to make:

  • I explicitly didn’t mention Helium-3. I think this is way oversold as a primary resource worth extracting on the Moon. The one fusion-power company that I think is credibly pushing using Helium-3 fusion (Helion Energy–a spinoff from MSNW) has a method they think can let them breed the Helium-3 from Deuterium. That said, during the discussion, it came up that there are existing, non-fusion energy terrestrial markets for Helium-3 and they never have enough of it. I don’t know how much demand there really is, but if you’re already strip-mining the lunar surface for other reasons, you might be able to sell a little He-3 on the side… maybe.
  • With all of the recent interest and development in metal 3d printing, the fact that there are meteoric nickel/iron particles in the lunar regolith that may be magnetically separatable could lead to an interesting 3d printing feedstock, if someone isn’t already looking into how to extract, purify, and print with those materials already.
  • I still think suitability for tourism and related industries is a seriously underappreciated resource for the Moon, especially as costs come down. The Moon has the “resource” of “location, location, location” going for it–it is really the only planetary destination off-earth that can be visited and returned from in less than a month. While a small number of rich adventurers have historically done very long vacations like African Safaris, the ability to go, have fun, and come back in a reasonable period of time is going to make a big difference in my opinion. One of the biggest deterrents to current orbital tourism on ISS has been not the cost, but the necessity to drop everything for 6 months of training in Russia. Most rich people are also busy people, and even with the most unrealistically amazing propulsion concepts on the books today, you’re probably talking at least a few months round-trip to go to Mars. For the foreseeable future, Mars will get settlers, while the Moon will get visitors10.

Cis-Lunar Markets (slides 18-23)
Paul Breed made the point yesterday that “When Guttenberg invented the printing press, he had no idea that Shakespeare would come along.” Ie that it’s often almost impossible to truly identify the true end-uses of new innovations. That said, while being a rather speculative endeavor, there are at least some concepts for markets of cislunar commerce that I think are worth discussing. By markets of cislunar commerce, I mean a market that involves leveraging in some way at least one lunar resource, instead of being entirely sourced from Earth. As each of these markets could be a blog post (or blog series of their own), I’m going to keep things high level so this blog post doesn’t end up too much longer than it already is:

  • On-orbit Manufactured Spacecraft (slide 19): The vast majority of economic activity in space to-date has involved “photon handling” of one sort or another–i.e. telecommunications, earth observation, and navigation. While all of the spacecraft used for these applications have so far been built on the ground, there are several groups who have identified the potential of on-orbit assembled spacecraft that are too big to be launched in once piece from the ground. Of all the things we could manufacture profitably in space, spacecraft seem like one of the most likely options. One of the more interesting ideas I’ve had is a spacecraft with enough power and aperture area11 to enable replacing rural cellphone towers. I’m not a telecomms expert, but AIUI, if you can throw a big enough aperture at it, you can receive even the faint signal from a terrestrial cellphone, and if you can throw enough aperture and power at it, you can send a spotbeam down with similar received power at the cellphone to what you’d receive from the cell tower. It always seemed to me that a big part of why satellite telephony took off was that cellphones got small a lot faster, and if you could have an existing cellphone switch from local cells to orbital ones when outside of the city, it seems like it would make things a lot easier than having tens or hundreds of thousands of rural cellphone towers throughout the world. If you can get the cost of materials and propellant from the Moon below the cost of launching them from Earth, this could be a big market for lunar resources. While that maybe hard to beat in LEO, for big GEO platforms, the Moon might have more of a fighting chance of beating even 2nd or 3rd generation RLVs.
  • Space Solar Power (slide 20): I won’t dismiss space solar power out of hand, but I’m pretty skeptical it will be able to compete with advances in nuclear fission or fusion as time goes on. People talk about powering remote bases and such, but those are precisely the places where you’d rather have an intermodal cargo container sized advanced nuclear plant rather than a large rectenna. The areas where space solar power are least unlikely to happen12 are areas where advanced nuclear would have a hard time, such as supersonic electric aircraft like I discussed in a previous blog post. There are a lot of details to be investigated to see if even these applications make sense, but they seem more likely than traditional baseload space solar power concepts. Especially if you can find a way to collocate them with and leverage the apertures you were using for telecommunications–the biggest benefit over batteries will be for transoceanic flights, which is precisely when a telecomm satellite has the least customers to service.
  • Propellant (slide 21): I’ve already talked about this a lot in this blog post. But it does really seem like things could change dramatically if distributed launch13 becomes an accepted launch operation. You might see a lot more direct GSO insertion missions instead of having the spacecraft use chemical or electric propulsion for orbit-raising from GTO to GEO. Not having to pack so much performance into every flight would allow more margins for engine-out or underperformance, or for launch vehicle reuse. The challenge is going to be if lunar resources can compete with RLVs and atmospheric gathering for the LEO market, because that’s probably where the biggest demand will be.
  • Settlement/Tourism (slide 22): One of the bigger lunar market will be supporting settlement and tourism throughout Cis-lunar space and beyond. I have a blog post I want to write tomorrow about a new (at least for me) angle that could potentially help drive at least LEO settlement. Similar considerations to the other two markets will apply though–the closer the resources are to the Moon, the more likely the Moon can be the best source for providing those resources. This is why lunar tourism is such an interesting market for lunar development, IMO.
  • Cyclers (slide 23): As I discussed previously under “real spaceships”, I think cyclers are going to be critical for any large-scale transportation of people to destinations like Mars. The idea of launching and landing and then relaunching all of the mass needed for Mars transit every time seems really, really silly to me. A modular, upgradeable, in-space only cycler system where for a given trip most of what you launch each time is just the people and goods they’re taking with them seems to make far more sense to me. If such an approach is taken, lunar materials could once again play a key role.

Anyhow, that’s a really long-winded version of my presentation, but it captures a lot of my thinking that I haven’t had a chance to fully discuss here on Selenian Boondocks yet, so I figured I’d share.

Posted in Altius Space Machines, Business, Commercial Space, ISRU, Launch Vehicles, Lunar Commerce, Lunar Exploration and Development, MHD Aerobraking and TPS, NASA, NEOs, Propellant Depots, Space Development, Space Settlement, Space Transportation, SpaceX, Technology, ULA, Variable Gravity | 36 Comments

Sea Launch Sold

I read just yesterday that Sea Launch has been sold. Then I get an email last night that this post from August 2014 inspired the purchase that solidified when SpaceX was able to recover on land the first try after banging the barge repeatedly. I wonder how much modification will be required to use the Falcon9 from the ocean platform.

Repost from 27 August 2014

Sea Launch has the sea going craft to launch large rockets at sea. They are also, according to rumors, not making quite as much money as the investors would prefer. It seems possible that they might be at least semi-motivated to sell off the under performing launch assets.

What if the real intention of SpaceX is to acquire those assets at bargain prices for use in house. Launch a few hundred miles at sea from Vandenburg for a feet dry landing there, with the actual launch location dictated by the desired launch azimuth. The first stage would never have an IIP intersecting property on land, while the second stage would have an IIP that moved fast enough to minimize theoretical injury and property damage probabilities. A day out to launch and a day back. Twice a week seems possible.

From Brownsville the trip would be even shorter. A quick run to a point that gave the right launch  azimuth and distance from the cape for a Falcon recovery there. Possibly a day trip with the launch frequency that implies if the business develops.

 

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Max Diameter Compensating Nozzle

One of the items that seems to be missing from the current crop of LVs is any hint of compensating Nozzles. So a nozzle normally flies that is over expanded at sea level, optimum for a few seconds at some intermediate altitude, and under expanded through most of the flight. The Isp hit from under expansion at altitude reduces the velocity attained by that booster, which is well known to hurt mass ratios even more. Perhaps worse is the thrust loss from over expansion at lift off. At lift off, every pound of lost thrust is perhaps 0.85 pounds less GLOW possible. I think compensating nozzles are, if obviously not essential, definitely a serious performance and thus profit enhancer.

One concept I believe to be original allows a single expansion nozzle for several chambers that is the full diameter of the launch vehicle. If an aerospike is a reversed bell nozzle in concept, then this one is partially re-reversing the aerospike while retaining the atmospheric wall through the lower altitude portions of the flight.

circumference nozzle exitIn this concept, the multiple engines are in a circle as far out as possible under the lower propellant tank. The expansion nozzles all are connected on the outer perimeter as well as completely enclosed in the center. When the ambient air is higher pressure than the  exhaust in the center volume, the flap valves hang open to let in the air. As air pressure decreases with altitude, the exhaust pressure gradually pushes the flaps closed. At high altitude the flaps are closed and sealed such that the multiple engines have a single expansion nozzle 12 feet or more in diameter giving the maximum possible expansion ratio.

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