Propellant Depot Heads Up

It probably won’t happen too soon, but I give a little heads up on this Altius Space Machines blog post about some depot orbital dynamics work I’m working with a friend on. Hope I have time to talk about it soon.

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Jonathan Goff

Jonathan Goff

President/CEO at Altius Space Machines
Jonathan Goff is a space technologist, inventor, and serial space entrepreneur who created the Selenian Boondocks blog. Jon was a co-founder of Masten Space Systems, and is the founder and CEO of Altius Space Machines, a space robotics startup in Broomfield, CO. His family includes his wife, Tiffany, and five boys: Jarom (deceased), Jonathan, James, Peter, and Andrew. Jon has a BS in Manufacturing Engineering (1999) and an MS in Mechanical Engineering (2007) from Brigham Young University, and served an LDS proselytizing mission in Olongapo, Philippines from 2000-2002.
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29 Responses to Propellant Depot Heads Up

  1. A_M_Swallow says:

    One thing to watch out for when designing a propellant depot – the Project Morpheus lunar lander uses liquid methane and LOX for propellant.

  2. AM,
    So? Once you’ve done LOX on-orbit, you know everything you need to know in order to do Methane, if customers really actually want to use it. My personal guess is still that most large customers will end up using LOX/LH2 for transfer stages, and something storable (NTO/MMH or maybe eventually NOFBX) for stationkeeping and satellite refueling. The only place I see a likely clear win for Methane as a fuel depot fluid is at Mars.

    ~Jon

  3. A_M_Swallow says:

    Some designs of depots can only use the same propellants as the supply vehicles.

  4. JohnHunt says:

    I understand that there are some challenging issues with the storage of liquid hydrogen. I read someone’s post and they listed abot 4 or 5 problems. Brittleness of very cold metals was one. Boiloff was another. I think that the lack of gravity to push the LH to the outlet was another. I think that there was something about the contraction of valves as well. Someone else posted that those problems have been solved in the last twenty years. Are there any outstanding issues that you know about?

    Also, is there enough solar energy to be able to electrolyze water on demand into useful quantities of fuel? Or would it take so long that you might as well just not include electrolysis with the fuel depot? Put another way, water from the Earth and Moon is stable and can easily be stored. Is there a place for a large water depot in LEO?

  5. JohnHunt says:

    Oh, and what do you think about the NASA announcement of $200 – $300 million for a LEO fuel depot?

  6. John,
    A lot of those have been discussed in my paper I did with the ULA and Boeing guys back in 2009, as well as some more recent papers. You can find that here: http://ulalaunch.com/site/docs/publications/PropellantDepots2009.pdf

    Summary:

    1-Hydrogen Embrittlement–There are plenty of materials used for propellant tanks that are ok as far as hydrogen embrittlement is concerned.
    2-Boiloff–The key is to limit heat flux into the tank as much as possible passively. LEO depots and even EML1/EML2 depots require stationkeeping burns to maintain their orbital position. If you can get the boiloff rates lower than the stationkeeping propellant consumption, you no longer have to completely cloes the Zero Boiloff problem.
    3-Settling–there are a lot of options out there for propellant settling. Propulsive and spin settling like what LM/ULA has favored. Zero-G propellant acquisition like Boeing prefers, Magnetic settling like U of Memphis likes, etc.
    4-Thermal expansion/contraction–this is a solved problem as far as I’m concerned. LH2 is used in industry every day, and while the solutions may not be perfect, they’re likely good enough.
    5-Electrolyzing water–This is power intensive enough that the only case it really makes solid sense is if you’re at or near a location where you can get ISRU water. Like on the Moon for instance. In LEO you’re better off shipping the LOX/LH2 and dealing with storage issues than trying to get enough power to do electrolysis.

    Also regarding your follow-on question, I think the study contract they’ve put out (which is much smaller than the actual hardware contract) is interesting, and a step in the right direction. Altius would love to be involved, but we’re too bandwidth constrained right now to put in our own contract. Hopefully when they release the actual hardware contract we can be a teaming partner on that with whoever wins.

    ~Jon

  7. Warren Platts says:

    “5-Electrolyzing water–This is power intensive enough that the only case it really makes solid sense is if you’re at or near a location where you can get ISRU water. Like on the Moon for instance. In LEO you’re better off shipping the LOX/LH2 and dealing with storage issues than trying to get enough power to do electrolysis.”

    I see Spudis and Lavoie’s paper calls for water cracking in orbital depots in both LEO and LLO or L1. You say you’re better off sending LOX/LH2 to LEO, but what about an L1/L2 station? Seems to me it’s possibly an unneeded duplication of effort since you would need a water cracking plant on the Lunar surface anyway.

  8. Warren,
    Admittedly, I haven’t done the trades, and the trades are likely subject to change as assumptions change. In the past it has seemed like getting enough power to crack water at a reasonable rate was going to require a *lot* of solar power acreage. Something that at least to me seems to be easier to do on the lunar surface than in space…but that may just be a personal bias.

    ~Jon

  9. Doug Jones says:

    I’d think that free space is far better for solar power than the lunar surface- no dust, no pesky nights, far lower structural requirements…

  10. Paul says:

    Whereas on the surface of the moon, you need a nuke. (The only way to be sure.)

    I wonder if, after this gas-station RfP, NASA will issue a RfP for mining water from non-terrestrial water?

  11. gbaikie says:

    What about beaming microwave power from earth to EML1 or lunar surface?

    I think one advantage of L-1 or L-2 in terms of using solar energy is it would be cheaper to ship from earth to L-1/2 than the Moon.
    If making any kind of solar panels on the Moon, then advantage goes to generating power on the Moon.

    I think in nearest term, one should focus on fuel depot rather than making water into LH2&LOX. Maybe you split some water into LH2&LOX- but also having some electrical power avail for other things which could be of more value.
    A fuel depot might be about “real estate”- and be a real space station, or base/town.

    Could there be added value being near a fuel depot, rather than in some other spot somewhere in space?
    One thing about “real estate” is someone is in control of the property [however that is defined] – they could to exclude some unwanted activity. Or have the right to have billboards [some people might not want that:)].
    What happens if someone wants drag space junk somewhere near the depot- maybe this good or maybe this bad, but one should have someone have a right to do this or right to prevent this from happening near someone which could affect them.
    A fuel depot might better as multiple entities rather a sole entity.
    So a community. A company which tows things, the company stores rocket fuel, and company that produces electrical power.
    And any rules that govern each of those entities can extended to apply to others- and therefore have a foundation of future laws.

  12. Paul Roberts says:

    >>What about beaming microwave power from earth to EML1 or lunar surface?

    Beaming power from GEO or MEO down to Earth has to deal with significant issues of beam spreading over the distances involved, (~22,000 miles for GEO). Spreading at LLO or EML-1 at ~200,000-250,000 miles would be nuts.

    You also have the problem that while a reciever at EML 1 would remain relatively stationary, the Earth will rotate under it meaning that power delivery to the reciever will not be constant.

    It’s not a credible option.
    Far easier to generate power on orbit.

    >>What happens if someone wants drag space junk somewhere near the depot- maybe this good or maybe this bad, but one should have someone have a right to do this or right to prevent this from happening near someone which could affect them.

    OK, this rambles a bit, but the only place where dragging space junk to any kind of depot makes any sense is in GEO and GEO “junk” is actually not very common. Most “junk ” is in LEO and LEO orbits are so numerous and the cost of moving items from any one orbital inclination to any other is so high, that no-one is going to be towing LEO junk anywhere. In GEO what you have is the possibility of placing a depot just below or above the commercial zone and then using a refuelable tug to move valuable comsats around. These comsats certainly don’t count as standard orbital “junk”, but, if they have failed, may count as salvage.

    Paul

  13. Paul says:

    gbaikie,
    “If making any kind of solar panels on the Moon, then advantage goes to generating power on the Moon.”

    Either you’re talking about a major fabrication plant, or very crappy solar panels. The first is a long way in the future, the other is a lot of work by a very limited very expensive workforce for not much net advantage over just shipping panels from Earth (or landing a reactor).

    I like the idea of beamed power though. I think that is the best way to develop SSPS; moon and Mars missions. Lower power requirements, hideously expensive alternatives (and hardly any environmentalists on site). Once the R&D’s paid off, it becomes cost effective for high-demand remote sites on Earth, like mining companies, military bases, post-disaster recovery, etc. Eventually you’re just another option on the table.

    “Could there be added value being near a fuel depot, rather than in some other spot somewhere in space?”

    Tele-op repair/refurbishment. a) You know that the fuel-station will get regular deliveries, if you can send up relatively small, low-mass parts alongside them, lowering your launch price. b) you know that either the fuel-customers are coming to you, or a refuelling tug is going out to them.

    Once you’re doing repair, you can add recovery. Buy the rights to dead satellites (guaranteeing to at least de-orbit.) Hire the tug to bring them back. If possible, tele-op a repair, refuel, and sell it on. If not, use it for parts. Deorbit anything you can’t use.

  14. gbaikie says:

    “Beaming power from GEO or MEO down to Earth has to deal with significant issues of beam spreading over the distances involved, (~22,000 miles for GEO). Spreading at LLO or EML-1 at ~200,000-250,000 miles would be nuts.”

    Perhaps it would be nuts.
    But sending energy from earth one wouldn’t need to be very efficient- if you could received 1/20th of the power sent it might be economical.

    “You also have the problem that while a reciever at EML 1 would remain relatively stationary, the Earth will rotate under it meaning that power delivery to the reciever will not be constant.”

    If if the cost of whatever system is generating the microwave energy on earth wasn’t very expensive, you could a have number of locations on earth beaming power. It seems main problem is somehow focusing the microwave so one has it concentrated enough at such great distance.

  15. gbaikie says:

    “The antenna, three-quarters the size of a football field, sent a 500-kilowatt strong, 90-minute long radar stream 231,800 miles to the Moon. The radar illuminated the rough-hewn lunar surface over an area measuring about 400 by 250 miles.”

    And:
    “In recent years, Earth-based radars have done a good job of mapping the south polar regions of the Moon. In 1997, Goldstone antennas scanned the area and produced maps with 75 meter resolution. In 2005, a team led by Don Campbell of Cornell University improved that figure to 20 meters using the giant Arecibo radar in Puerto Rico and the Green Bank Telescope in West Virginia (D. B. Campbell et al, Nature, 443, 835-837, 2006). The JPL survey reported in this story also achieved 20 meter resolution.”

    When they say illuminated 400 by 250 miles- does that mean an area scanned [therefore why it’s taking 90 minutes] or is a circular disk illuminating an oval shape which 400 by 250 miles which is held pointing at one location for 90 minutes.
    Would the reason one has 75 or 20 meter resolution be because of
    beam spreading?
    And if so doesn’t that indicate that perhaps if using something like Interferometry in sending a signal one could reduce beam spreading.

  16. gbaikie says:

    “Near-Earth asteroid 2005 YU55 will pass within 0.85 lunar distances from the Earth on November 8, 2011.”

    “Using the Goldstone radar operating in a relatively new “chirp” mode, the November 2011 radar opportunity could result in a shape model reconstruction with a resolution of as fine as 4 meters.”
    http://thewatchers.adorraeli.com/2011/03/13/asteroid-2005-yu55-to-approach-earth-on-nov-8th-2011/

  17. gbaikie says:

    I would suggest the following:
    Make 3 radio telescopes which can send a radar signal and have place at different longitudes and at a distance in which all three can “see” the same moon. Use existing radio telescopes but modify them to send a radar signal. Try to have the 3 of them in a straight line.
    Have all three radar signals from the radio telescope aimed at the surface of the Moon. And have a large radio telescope detect the return signal. Analysis that return signal.
    You might pick an Apollo landing site so it’s in the microwaved area.
    Also you try crossing the signals- aim three signals at L-1 and measure the return signal from the Moon. And try other distances from the Moon as the point all three telescopes are aiming at.

  18. gbaikie says:

    “Either you’re talking about a major fabrication plant, or very crappy solar panels”
    I was thinking of very crappy solar panels.

    “the other is a lot of work by a very limited very expensive workforce for not much net advantage over just shipping panels from Earth (or landing a reactor).”
    Yes, question how much net advantage if any. It could not be economical.

    “I like the idea of beamed power though. I think that is the best way to develop SSPS; moon and Mars missions. Lower power requirements, hideously expensive alternatives (and hardly any environmentalists on site). Once the R&D’s paid off, it becomes cost effective for high-demand remote sites on Earth, like mining companies, military bases, post-disaster recovery, etc. Eventually you’re just another option on the table.”

    I agree that the best way of getting to the point beaming energy to earth, would be to first beam energy from earth to space.
    At the moment electrical energy on earth is hundreds of times cheaper than in space.
    So, in terms of getting to point of beaming energy from space to Earth, the most important and first thing needed is for there to a market in space for electrical power.
    I am not particularly picky where in space there is a market for electrical energy, nor do care much, on how much it costs per kW/h.
    What care most about is having enough electrical power available- a 1 kW would be nice but a 1 mW power “supply” would be better.
    And what is most important how much kw/h any buyer can buy in a given period of time. So if one buy say 1000 kw/h in a period of one year time- that much better than what we got now. If a buyer can buy 1 million kW/h in a period of a year that’s “a thousand times” better. And of course being able to buy 1000 kW/h in a month’s time is better than if in 1 year’s time.

  19. Paul Roberts says:

    @gbaikie

    While generating power on Earth is a small fraction of what it would cost in orbit, you have to take a look at what it would cost to build the antenna in orbit. If the dispersal is such that you can receive more power directly as solar (with the newer ~25-30% efficient cells) than as beamed power, then it makes far more sense to generate your own power in orbit.

    Also, even if you have several stations on Earth beaming up to a station, their efficiency is lower unless the reciever is directly overhead caused by the angle between them. At the very least you will have tripled your energy producing costs and increased the size of the reciever to account for the angle losses. In actuality, the size of the power plants will have to be larger than you would need for direct beaming and you will probably need more than three of them to provide adequate coverage. Take a look at the equator. An awful lot of it is covered by water. Building power plants off the plane of the equator to find solid land will cost again you in terms of efficiency. All of a suddden, it’s not so cheap to produce on Earth anymore.

    Paul

  20. gbaikie says:

    “While generating power on Earth is a small fraction of what it would cost in orbit, you have to take a look at what it would cost to build the antenna in orbit. If the dispersal is such that you can receive more power directly as solar (with the newer ~25-30% efficient cells) than as beamed power, then it makes far more sense to generate your own power in orbit. ”

    Yeah that is good point. I don’t know enough about it, just more questions:) Another question is how much energy could the antenna receive per square meter.
    We could assume for the moment the amount power send from earth is not limited- except that powerful beams could be dangerous for anything in the beam area- powerful enough microwave is consider a potential weapon and besides injuring humans can destroy electronics. And finally affect any other microwave signal [commonly used in communication] not in the direct path.
    Let’s start with a known. A 70 meter diameter radio telescope has beamed 500 kW. 70 diameter is radius squared times pi= 3848 sq meters which only .1299 kW [1299 watts] per square meter- a signal about as strong as sunlight itself. It seems one would need to increase the signal per square meter by about 100 times this- just to get somewhere in the ballpark. The military has tested weapons which is much higher this this per sq meter. As a guess as high as 100 times per square meter, but I doubt much higher or as high as 1000 times this signal strength per square meter. Though perhaps anything in range of 10 kW per square meter could do things like bring airplanes crashing to the ground, destroy satellites, etc.
    Anyhow we could say one need get say, 1 kW per sq at the L-1 point. Then question is how mass per square meter is the rectenna
    as compared to solar panels. If it’s the same mass or more, the idea gets “difficult” as in intenable.

  21. gbaikie says:

    “Also, even if you have several stations on Earth beaming up to a station, their efficiency is lower unless the reciever is directly overhead caused by the angle between them. At the very least you will have tripled your energy producing costs and increased the size of the reciever to account for the angle losses.”

    I doubt even with heavy cloud cover it would lose a 2/3 of the signal- it’s transparent to to atmosphere and can “see” thru clouds. You wouldn’t want to beam near the horizon. Perhaps a 45 degree angle, maybe as low as 30. I think how much airspace you would allowed to use, could be bigger factor- coupled with any possible disruption in other communication- lower towards the horizon the larger this effect could be.

  22. Vladislaw says:

    I have absolutely no clue on microwave beaming, other than surface reading of articles. What about if you used sats in GEO as relays. Beam to them and they relay the power to the more distant receivers? Or is so much lost in the swaps that it is just cheaper to do produce energy locally.

  23. gbaikie says:

    “In actuality, the size of the power plants will have to be larger than you would need for direct beaming and you will probably need more than three of them to provide adequate coverage. Take a look at the equator. An awful lot of it is covered by water. Building power plants off the plane of the equator to find solid land will cost again you in terms of efficiency. All of a suddden, it’s not so cheap to produce on Earth anymore.”

    Oh, I meant 3 to test a signal reflected back from the moon. If you want constant power, you need a lot more than 3. Something on the order of a dozen. Though if beaming from nearer the either of earth’s poles, maybe you could use around 3 or 6.
    I didn’t calculate it, but as far using 3 station they could be spread out by hundreds miles or in range of a 1000 or two miles. On the equator since earth is about 25000 miles in circumference, at thousand mile separation it’s only 3000 miles of that 25,000 distance- 1/8th. If testing radar on the moon, the less powerful the signal and less focused the beam the closer they should be to each other. And one can use less signal strength if whatever receiver of bouncing signal is larger. So should consider the nature of existing radio telescope network- and also “amateur” ham radio network before making any plans in this regard.

  24. gbaikie says:

    “I have absolutely no clue on microwave beaming, other than surface reading of articles. What about if you used sats in GEO as relays. Beam to them and they relay the power to the more distant receivers? Or is so much lost in the swaps that it is just cheaper to do produce energy locally.”

    Well it’s easy to bounce a signal. In terms of space to space, you have “an infinte” wave band. In regards to earth you limited to wave spectrum to what wave length is transparent to the Earth atmosphere- the mass of earth atmosphere is equal to around 30 meters of liquid air -which is fairly transparent to some wave lengths- it will block x-ray and harmful ultraviolet emitted by the sun.
    In the infrared or visible wavelength the atmosphere at noon blocks about 30% of this “signal” known as sunlight.
    So since you have wide selection of wave band in space, you could pick one which reflective to certain materials. So you might start with idea what’s cheapest thing which can cover a large area in space and pick a wavelength that is reflective to it.
    Cheap in terms of somehow shipping it up there.

  25. gbaikie says:

    A similar topic, is you could increase the energy produced by a solar panel in Earth/Moon L-1 by beaming a wavelength which that solar panel is most efficient in converting to electrical power- using LED lasers which capable controlling the wave length they emit. So you could double or tripe the power of a solar power panel [or more].

  26. gbaikie says:

    Oh you try it out on any satellite which has degraded solar panel and needs more electrical power to operate well.
    One problem is the solar panel need to be facing in your direction, so you only can do it 1/2 of the time the satellite in is orbit- unless you put a mirror in say Earth/Sun L-1, or 3 mirrors in a higher orbit than GEO

  27. Nels says:

    JohnHunt >>> Also, is there enough solar energy to be able to electrolyze water on demand into useful quantities of fuel? Or would it take so long that you might as well just not include electrolysis with the fuel depot? Put another way, water from the Earth and Moon is stable and can easily be stored. Is there a place for a large water depot in LEO?

    Spudis & Lavoie figure about a tonne of propellant (O/F = 6) produced annually, plus residual oxygen, for each kilowatt of electricity (though when they quote power requirements, they seem to be averaged over an orbit, not peak power). That corresponds to an efficiency of 65%, which doesn’t seem to outrageous. So, we’re talking roughly ISS-sized solar arrays to produce dozens of tonnes per year. Not small, but not obviously outrageous. But it does mean that, lacking in situ manufacturing of PV panels, all propellant to be supplied in LEO should be cracked in LEO, so the significant PV panel mass doesn’t need to be shipped any further out of earth’s gravity well then needed. Likewise, propellant to be supplied at a Lagrangian staging point should be produced there rather than on the moon.

    Please note, everybody, that the names of generic chemicals — methane, helium, water, graphite, etc. — are *not* capitalized.

  28. Nels says:

    P.S. I surrounded tags the last paragraph of the preceding message with a matching pair of HTML-style “rant tags (i.e., “” and “” without the extraneous spaces), thinking that they would not be processed and would visible so as to indicate my less-than-serious tone.

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