NASA picks SSL to develop key fuel depot technology

SSL, a Maxar Technologies company (formerly MacDonald, Dettwiler and Associates Ltd.) a leading provider of innovative satellites and spacecraft systems, was selected by NASA for two separate public-private partnerships to develop two vital “Tipping Point” spacecraft technologies.

Maxar has over $2 billion in revenue and 6500 employees. SSL builds advanced robotic and servicing systems for nuclear, military, agriculture and infrastructure application. SSL robotics technologies are proven on the Space Shuttle, the International Space Station and the Mars lander and rovers.

SSL works with NASA and DARPA with robotic assembly in space and robotic servicing of satellites.

NASA’s Tipping Point awards are designed to foster the development of commercial space capabilities and benefit future NASA missions. A technology is considered by NASA to be at a tipping point if an investment in a demonstration is likely to result in a high likelihood of infusion into a commercial space application, and significant improvement in the ability to successfully bring the technology to market.

The company will develop two technologies aim to expand the capabilities and resiliency of spacecraft through in-orbit refueling for electric propulsion and enabling space transportation with highly efficient, high-power solar electric propulsion. These innovations demonstrate SSL’s ongoing commitment to, and expanding role in, the development of next-generation space infrastructure.

* In-Space Xenon Transfer for Satellite, Servicing and Exploration Vehicle Replenishment and Life Extension will unlock new possibilities for on-orbit servicing and refueling by demonstrating that fuel transfer can be performed reliably in space.

* High Efficiency 6kW Dual Mode Electric Propulsion Engine for Broad Mission Applications technology will leverage SSL’s long history of innovation in electric propulsion to develop a highly flexible, dual-mode power processing unit capable of providing variable voltage, increasing overall mission efficiency and providing greater power, flexibility, and velocity for future missions.

“SSL is a leader in electric propulsion and robotics for space missions and is uniquely positioned to help U.S. government agencies achieve their goals with confidence,” said Richard White, president of SSL Government Systems. “Powerful and cost-effective propulsion systems and reuse of assets already on-orbit will ultimately help build a better world and propel humanity’s exploration of space.”

90 thoughts on “NASA picks SSL to develop key fuel depot technology”

  1. It sure would be nice to see NASA get serious about on-orbit cryogenic propellant transfer. Electric propellant is all well and good for satellite servicing, but it’s not going to get you tens of tonnes of payload to the lunar or martian surface. Of course, that’s exactly why they’re [i]not[/i] pursuing it. Anything that would undermine SLS isn’t going to be tolerated.

    Reply
  2. It sure would be nice to see NASA get serious about on-orbit cryogenic propellant transfer. Electric propellant is all well and good for satellite servicing but it’s not going to get you tens of tonnes of payload to the lunar or martian surface.Of course that’s exactly why they’re [i]not[/i] pursuing it. Anything that would undermine SLS isn’t going to be tolerated.

    Reply
  3. Not really my area but I suspect that 90% of the tech developed to transfer xenon propellant would be directly applicable to transferring other fluids.

    Reply
  4. That’s most likely exactly it. There are already trade studies done for optimal locations per architecture setup, even getting down to the detail of “lunar surface gas station fueled by ISRU” vs. lunar orbital depot vs. GEO depot vs. L2 depot and all the delta-V’s inbetween, which would degrade the desire for SLS.

    Reply
  5. Not really my area but I suspect that 90{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of the tech developed to transfer xenon propellant would be directly applicable to transferring other fluids.

    Reply
  6. That’s most likely exactly it. There are already trade studies done for optimal locations per architecture setup even getting down to the detail of lunar surface gas station fueled by ISRU”” vs. lunar orbital depot vs. GEO depot vs. L2 depot and all the delta-V’s inbetween”””” which would degrade the desire for SLS.”””

    Reply
  7. The big differences: 1) Lifetime of the propellant on-orbit. Xenon can be stored for years. Cryogenics can currently be stored for hours. The technology needs to be matured to get that up to at least weeks. 2) Volume transferred. For servicing birds with electric thrusters, you’re talking about transferring a few kg. The PPE for the LOP is talking about a couple of tonnes. But you’d have to transfer tens of tonnes to do on-orbit cryogenic refueling. 3) I’m on thin ice on this one, but your mating systems, connectors, and piping are going to be a lot easier at 165 K for Xenon than they are at 90 K for LOX, 111 K for LCH4, or 20 K for LH2.

    Reply
  8. The big differences:1) Lifetime of the propellant on-orbit. Xenon can be stored for years. Cryogenics can currently be stored for hours. The technology needs to be matured to get that up to at least weeks.2) Volume transferred. For servicing birds with electric thrusters you’re talking about transferring a few kg. The PPE for the LOP is talking about a couple of tonnes. But you’d have to transfer tens of tonnes to do on-orbit cryogenic refueling.3) I’m on thin ice on this one but your mating systems connectors and piping are going to be a lot easier at 165 K for Xenon than they are at 90 K for LOX 111 K for LCH4 or 20 K for LH2.

    Reply
  9. For the storage part, I would guess that a good solar shade should be enough to minimize methane and LOX evaporation, since space is pretty cold in the shadows. You’d still need the right tank materials, but we have experience with LNG and LOX tanks down here on Earth. The inner lining and overall structure would likely be similar, but you may want lighter structural and insulation materials and some extra layers on the outside. The experience from ISS and heatshields may be applicable. It should be possible to store and transfer LOX and methane at nearly the same temperature, with some insulation between them, since oxygen’s boiling point and methane’s melting point are both near 90K. Unfortunately, methane’s melting point is just a bit higher, and you don’t want the methane to freeze or the oxygen to boil, so you’d need to keep the oxygen at a slightly lower temperature. Maybe it’s possible to mix in a small fraction of some other gas (hydrogen? propane?) to get these temperatures to overlap. Either way, one could probably design a single system for a common temperature range, which saves some on engineering. Hydrogen is quite a bit harder on all counts, which is part of why SpaceX chose methalox.

    Reply
  10. For the storage part I would guess that a good solar shade should be enough to minimize methane and LOX evaporation since space is pretty cold in the shadows. You’d still need the right tank materials but we have experience with LNG and LOX tanks down here on Earth. The inner lining and overall structure would likely be similar but you may want lighter structural and insulation materials and some extra layers on the outside. The experience from ISS and heatshields may be applicable.It should be possible to store and transfer LOX and methane at nearly the same temperature with some insulation between them since oxygen’s boiling point and methane’s melting point are both near 90K. Unfortunately methane’s melting point is just a bit higher and you don’t want the methane to freeze or the oxygen to boil so you’d need to keep the oxygen at a slightly lower temperature. Maybe it’s possible to mix in a small fraction of some other gas (hydrogen? propane?) to get these temperatures to overlap. Either way one could probably design a single system for a common temperature range which saves some on engineering.Hydrogen is quite a bit harder on all counts which is part of why SpaceX chose methalox.

    Reply
  11. I don’t think there are any insurmountable problems with cryogenic refueling, but there’s a huge amount of technology readiness work that needs to be done. One example: You’d like to be able to reuse the same cryo couplers that you fill/drain the vehicle on the pad once you’re in space, but the T-0 breakaways don’t currently allow that. Here (http://www.altius-space.com/cryo-coupler-sbir-phase-ii-win/ ) is a company that’s working on developing a common cryo coupler. Other things: Orbital rendezvous for prop depots isn’t exactly straightforward, because you have to make the prop depot orbital elements compatible with the BEO departure orbit. There’s some work that’s being done in this area, but it’s quite likely that a long-dwell depot won’t be possible first time out of the chute. Then there’s the whole issue of allowing heat into the system through the docking and coupling mechanisms, as well as managing power to the depot without warming it up. You’ve got issues surrounding ground radiation if you want to do refueling on the Moon, along with making the whole system safe in the presence of lunar dust. Finally, note that, while methane is awesome if you’re launching it from Earth, it’s not possible to manufacture it on the lunar surface without a source of carbon. So there are lots of logistical problems associated with developing either a mixed methane/hydrogen propellant economy, or in delivering a carbon source to the Moon. Bottom line: As with everything else that has to do with space, getting the technology to be ready is about two orders of magnitude more work than developing the conceptual architecture. That’s why it would be nice to see NASA get serious about it. But I’m not holding my breath.

    Reply
  12. I don’t think there are any insurmountable problems with cryogenic refueling but there’s a huge amount of technology readiness work that needs to be done.One example: You’d like to be able to reuse the same cryo couplers that you fill/drain the vehicle on the pad once you’re in space but the T-0 breakaways don’t currently allow that. Here (http://www.altius-space.com/cryo-coupler-sbir-phase-ii-win/ ) is a company that’s working on developing a common cryo coupler.Other things: Orbital rendezvous for prop depots isn’t exactly straightforward because you have to make the prop depot orbital elements compatible with the BEO departure orbit. There’s some work that’s being done in this area but it’s quite likely that a long-dwell depot won’t be possible first time out of the chute.Then there’s the whole issue of allowing heat into the system through the docking and coupling mechanisms as well as managing power to the depot without warming it up. You’ve got issues surrounding ground radiation if you want to do refueling on the Moon along with making the whole system safe in the presence of lunar dust.Finally note that while methane is awesome if you’re launching it from Earth it’s not possible to manufacture it on the lunar surface without a source of carbon. So there are lots of logistical problems associated with developing either a mixed methane/hydrogen propellant economy or in delivering a carbon source to the Moon.Bottom line: As with everything else that has to do with space getting the technology to be ready is about two orders of magnitude more work than developing the conceptual architecture. That’s why it would be nice to see NASA get serious about it. But I’m not holding my breath.

    Reply
  13. If you were trying to post a link there, you’ll need to break it up to pass Vuukle’s filters. Something like: example com /path/to/resource Re methalox on the moon, at least on the conceptual level, the easiest path is to bring carbon from Earth. The carbon is only 15% of the methalox mass, so that still lets you multiply your fuel supply by ~6.7 times with the same mass budget. Basically, once you have LOX production on the Moon, it’s not too hard to upgrade for making hydrolox. It’s mostly the same equipment. And once you have hydrolox production, you’re just one reactor short of methalox production. You need to react the hydrogen with carbon to make methane; the rest of the equipment is the same. If you want to get more fancy, you can react the carbon with water first, to get syngas, and then run that through Sabatier. That should also work better with asteroidal carbon. But it’s more complicated, so can be done later. Handling the carbon shouldn’t be too different from handling regolith, which isn’t straightforward, but you’d need to do that anyway to make LOX or hydrolox. In theory, by my calculations, a single fully refueled BFS should be able to land all the equipment necessary to start methalox production, plus enough carbon for the return trip. But it might take a while to make enough methalox to send it back.

    Reply
  14. Increasing the methane pressure would push its melting point higher, but you could compensate by increasing the oxygen pressure some more. So yes, that should work. Good point.

    Reply
  15. If you were trying to post a link there you’ll need to break it up to pass Vuukle’s filters. Something like: example com /path/to/resourceRe methalox on the moon at least on the conceptual level the easiest path is to bring carbon from Earth. The carbon is only 15{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of the methalox mass so that still lets you multiply your fuel supply by ~6.7 times with the same mass budget. Basically once you have LOX production on the Moon it’s not too hard to upgrade for making hydrolox. It’s mostly the same equipment. And once you have hydrolox production you’re just one reactor short of methalox production. You need to react the hydrogen with carbon to make methane; the rest of the equipment is the same.If you want to get more fancy you can react the carbon with water first to get syngas and then run that through Sabatier. That should also work better with asteroidal carbon. But it’s more complicated so can be done later.Handling the carbon shouldn’t be too different from handling regolith which isn’t straightforward but you’d need to do that anyway to make LOX or hydrolox. In theory by my calculations a single fully refueled BFS should be able to land all the equipment necessary to start methalox production plus enough carbon for the return trip. But it might take a while to make enough methalox to send it back.

    Reply
  16. Increasing the methane pressure would push its melting point higher but you could compensate by increasing the oxygen pressure some more. So yes that should work. Good point.

    Reply
  17. 75% are carbonaceous (I’m guessing a typo). But one of the links below suggests that most of that carbon would vaporize on impact. Whatever is left would be bombarded by the solar wind, which I think should produce various volatiles (methane etc). Some of carbon may react with oxides in the regolith to form CO/CO2 and other carbon compounds. But depending on the various rates etc, some of the carbon may survive. And I’d expect the volatiles to collect in cold traps, similar to water. AFAIK, there weren’t that many efforts to look for carbon deposits on the Moon, since by standard assumptions it’s not that interesting. Lunar ISRU is only recently gaining interest, let alone methalox production. For structural materials, the high-performance ones (carbon fiber, CNTs, etc) are still difficult to make. So aside from scientific curiosity, the focus has been on water and metals. However, a google search for “carbon on the moon” does reveal some evidence for carbon: asi org /adb/m/08/08/lunar-carbon html nature com /articles/ngeo2530 (paywall) mnn com /earth-matters/space/stories/carbon-rich-graphite-discovered-on-the-moon hou usra edu /meetings/lpsc2016/pdf/1415 pdf According to the last pdf, impact carbon is up to 400 ppm.

    Reply
  18. 75{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} are carbonaceous (I’m guessing a typo). But one of the links below suggests that most of that carbon would vaporize on impact. Whatever is left would be bombarded by the solar wind which I think should produce various volatiles (methane etc). Some of carbon may react with oxides in the regolith to form CO/CO2 and other carbon compounds. But depending on the various rates etc some of the carbon may survive. And I’d expect the volatiles to collect in cold traps similar to water.AFAIK there weren’t that many efforts to look for carbon deposits on the Moon since by standard assumptions it’s not that interesting. Lunar ISRU is only recently gaining interest let alone methalox production. For structural materials the high-performance ones (carbon fiber CNTs etc) are still difficult to make. So aside from scientific curiosity the focus has been on water and metals.However a google search for carbon on the moon”” does reveal some evidence for carbon:asi org /adb/m/08/08/lunar-carbon htmlnature com /articles/ngeo2530 (paywall)mnn com /earth-matters/space/stories/carbon-rich-graphite-discovered-on-the-moonhou usra edu /meetings/lpsc2016/pdf/1415 pdfAccording to the last pdf”””” impact carbon is up to 400 ppm.”””

    Reply
  19. 75% are carbonaceous (I’m guessing a typo). But one of the links below suggests that most of that carbon would vaporize on impact. Whatever is left would be bombarded by the solar wind, which I think should produce various volatiles (methane etc). Some of carbon may react with oxides in the regolith to form CO/CO2 and other carbon compounds. But depending on the various rates etc, some of the carbon may survive. And I’d expect the volatiles to collect in cold traps, similar to water. AFAIK, there weren’t that many efforts to look for carbon deposits on the Moon, since by standard assumptions it’s not that interesting. Lunar ISRU is only recently gaining interest, let alone methalox production. For structural materials, the high-performance ones (carbon fiber, CNTs, etc) are still difficult to make. So aside from scientific curiosity, the focus has been on water and metals. However, a google search for “carbon on the moon” does reveal some evidence for carbon: asi org /adb/m/08/08/lunar-carbon html nature com /articles/ngeo2530 (paywall) mnn com /earth-matters/space/stories/carbon-rich-graphite-discovered-on-the-moon hou usra edu /meetings/lpsc2016/pdf/1415 pdf According to the last pdf, impact carbon is up to 400 ppm.

    Reply
  20. 75{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} are carbonaceous (I’m guessing a typo). But one of the links below suggests that most of that carbon would vaporize on impact. Whatever is left would be bombarded by the solar wind which I think should produce various volatiles (methane etc). Some of carbon may react with oxides in the regolith to form CO/CO2 and other carbon compounds. But depending on the various rates etc some of the carbon may survive. And I’d expect the volatiles to collect in cold traps similar to water.AFAIK there weren’t that many efforts to look for carbon deposits on the Moon since by standard assumptions it’s not that interesting. Lunar ISRU is only recently gaining interest let alone methalox production. For structural materials the high-performance ones (carbon fiber CNTs etc) are still difficult to make. So aside from scientific curiosity the focus has been on water and metals.However a google search for carbon on the moon”” does reveal some evidence for carbon:asi org /adb/m/08/08/lunar-carbon htmlnature com /articles/ngeo2530 (paywall)mnn com /earth-matters/space/stories/carbon-rich-graphite-discovered-on-the-moonhou usra edu /meetings/lpsc2016/pdf/1415 pdfAccording to the last pdf”””” impact carbon is up to 400 ppm.”””

    Reply
  21. 75% are carbonaceous (I’m guessing a typo). But one of the links below suggests that most of that carbon would vaporize on impact. Whatever is left would be bombarded by the solar wind, which I think should produce various volatiles (methane etc). Some of carbon may react with oxides in the regolith to form CO/CO2 and other carbon compounds. But depending on the various rates etc, some of the carbon may survive. And I’d expect the volatiles to collect in cold traps, similar to water.

    AFAIK, there weren’t that many efforts to look for carbon deposits on the Moon, since by standard assumptions it’s not that interesting. Lunar ISRU is only recently gaining interest, let alone methalox production. For structural materials, the high-performance ones (carbon fiber, CNTs, etc) are still difficult to make. So aside from scientific curiosity, the focus has been on water and metals.

    However, a google search for “carbon on the moon” does reveal some evidence for carbon:
    asi org /adb/m/08/08/lunar-carbon html
    nature com /articles/ngeo2530 (paywall)
    mnn com /earth-matters/space/stories/carbon-rich-graphite-discovered-on-the-moon
    hou usra edu /meetings/lpsc2016/pdf/1415 pdf

    According to the last pdf, impact carbon is up to 400 ppm.

    Reply
  22. If you were trying to post a link there, you’ll need to break it up to pass Vuukle’s filters. Something like: example com /path/to/resource Re methalox on the moon, at least on the conceptual level, the easiest path is to bring carbon from Earth. The carbon is only 15% of the methalox mass, so that still lets you multiply your fuel supply by ~6.7 times with the same mass budget. Basically, once you have LOX production on the Moon, it’s not too hard to upgrade for making hydrolox. It’s mostly the same equipment. And once you have hydrolox production, you’re just one reactor short of methalox production. You need to react the hydrogen with carbon to make methane; the rest of the equipment is the same. If you want to get more fancy, you can react the carbon with water first, to get syngas, and then run that through Sabatier. That should also work better with asteroidal carbon. But it’s more complicated, so can be done later. Handling the carbon shouldn’t be too different from handling regolith, which isn’t straightforward, but you’d need to do that anyway to make LOX or hydrolox. In theory, by my calculations, a single fully refueled BFS should be able to land all the equipment necessary to start methalox production, plus enough carbon for the return trip. But it might take a while to make enough methalox to send it back.

    Reply
  23. If you were trying to post a link there you’ll need to break it up to pass Vuukle’s filters. Something like: example com /path/to/resourceRe methalox on the moon at least on the conceptual level the easiest path is to bring carbon from Earth. The carbon is only 15{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of the methalox mass so that still lets you multiply your fuel supply by ~6.7 times with the same mass budget. Basically once you have LOX production on the Moon it’s not too hard to upgrade for making hydrolox. It’s mostly the same equipment. And once you have hydrolox production you’re just one reactor short of methalox production. You need to react the hydrogen with carbon to make methane; the rest of the equipment is the same.If you want to get more fancy you can react the carbon with water first to get syngas and then run that through Sabatier. That should also work better with asteroidal carbon. But it’s more complicated so can be done later.Handling the carbon shouldn’t be too different from handling regolith which isn’t straightforward but you’d need to do that anyway to make LOX or hydrolox. In theory by my calculations a single fully refueled BFS should be able to land all the equipment necessary to start methalox production plus enough carbon for the return trip. But it might take a while to make enough methalox to send it back.

    Reply
  24. Increasing the methane pressure would push its melting point higher, but you could compensate by increasing the oxygen pressure some more. So yes, that should work. Good point.

    Reply
  25. Increasing the methane pressure would push its melting point higher but you could compensate by increasing the oxygen pressure some more. So yes that should work. Good point.

    Reply
  26. I don’t think there are any insurmountable problems with cryogenic refueling, but there’s a huge amount of technology readiness work that needs to be done. One example: You’d like to be able to reuse the same cryo couplers that you fill/drain the vehicle on the pad once you’re in space, but the T-0 breakaways don’t currently allow that. Here (http://www.altius-space.com/cryo-coupler-sbir-phase-ii-win/ ) is a company that’s working on developing a common cryo coupler. Other things: Orbital rendezvous for prop depots isn’t exactly straightforward, because you have to make the prop depot orbital elements compatible with the BEO departure orbit. There’s some work that’s being done in this area, but it’s quite likely that a long-dwell depot won’t be possible first time out of the chute. Then there’s the whole issue of allowing heat into the system through the docking and coupling mechanisms, as well as managing power to the depot without warming it up. You’ve got issues surrounding ground radiation if you want to do refueling on the Moon, along with making the whole system safe in the presence of lunar dust. Finally, note that, while methane is awesome if you’re launching it from Earth, it’s not possible to manufacture it on the lunar surface without a source of carbon. So there are lots of logistical problems associated with developing either a mixed methane/hydrogen propellant economy, or in delivering a carbon source to the Moon. Bottom line: As with everything else that has to do with space, getting the technology to be ready is about two orders of magnitude more work than developing the conceptual architecture. That’s why it would be nice to see NASA get serious about it. But I’m not holding my breath.

    Reply
  27. I don’t think there are any insurmountable problems with cryogenic refueling but there’s a huge amount of technology readiness work that needs to be done.One example: You’d like to be able to reuse the same cryo couplers that you fill/drain the vehicle on the pad once you’re in space but the T-0 breakaways don’t currently allow that. Here (http://www.altius-space.com/cryo-coupler-sbir-phase-ii-win/ ) is a company that’s working on developing a common cryo coupler.Other things: Orbital rendezvous for prop depots isn’t exactly straightforward because you have to make the prop depot orbital elements compatible with the BEO departure orbit. There’s some work that’s being done in this area but it’s quite likely that a long-dwell depot won’t be possible first time out of the chute.Then there’s the whole issue of allowing heat into the system through the docking and coupling mechanisms as well as managing power to the depot without warming it up. You’ve got issues surrounding ground radiation if you want to do refueling on the Moon along with making the whole system safe in the presence of lunar dust.Finally note that while methane is awesome if you’re launching it from Earth it’s not possible to manufacture it on the lunar surface without a source of carbon. So there are lots of logistical problems associated with developing either a mixed methane/hydrogen propellant economy or in delivering a carbon source to the Moon.Bottom line: As with everything else that has to do with space getting the technology to be ready is about two orders of magnitude more work than developing the conceptual architecture. That’s why it would be nice to see NASA get serious about it. But I’m not holding my breath.

    Reply
  28. For the storage part, I would guess that a good solar shade should be enough to minimize methane and LOX evaporation, since space is pretty cold in the shadows. You’d still need the right tank materials, but we have experience with LNG and LOX tanks down here on Earth. The inner lining and overall structure would likely be similar, but you may want lighter structural and insulation materials and some extra layers on the outside. The experience from ISS and heatshields may be applicable. It should be possible to store and transfer LOX and methane at nearly the same temperature, with some insulation between them, since oxygen’s boiling point and methane’s melting point are both near 90K. Unfortunately, methane’s melting point is just a bit higher, and you don’t want the methane to freeze or the oxygen to boil, so you’d need to keep the oxygen at a slightly lower temperature. Maybe it’s possible to mix in a small fraction of some other gas (hydrogen? propane?) to get these temperatures to overlap. Either way, one could probably design a single system for a common temperature range, which saves some on engineering. Hydrogen is quite a bit harder on all counts, which is part of why SpaceX chose methalox.

    Reply
  29. For the storage part I would guess that a good solar shade should be enough to minimize methane and LOX evaporation since space is pretty cold in the shadows. You’d still need the right tank materials but we have experience with LNG and LOX tanks down here on Earth. The inner lining and overall structure would likely be similar but you may want lighter structural and insulation materials and some extra layers on the outside. The experience from ISS and heatshields may be applicable.It should be possible to store and transfer LOX and methane at nearly the same temperature with some insulation between them since oxygen’s boiling point and methane’s melting point are both near 90K. Unfortunately methane’s melting point is just a bit higher and you don’t want the methane to freeze or the oxygen to boil so you’d need to keep the oxygen at a slightly lower temperature. Maybe it’s possible to mix in a small fraction of some other gas (hydrogen? propane?) to get these temperatures to overlap. Either way one could probably design a single system for a common temperature range which saves some on engineering.Hydrogen is quite a bit harder on all counts which is part of why SpaceX chose methalox.

    Reply
  30. If you were trying to post a link there, you’ll need to break it up to pass Vuukle’s filters. Something like: example com /path/to/resource

    Re methalox on the moon, at least on the conceptual level, the easiest path is to bring carbon from Earth. The carbon is only 15% of the methalox mass, so that still lets you multiply your fuel supply by ~6.7 times with the same mass budget.

    Basically, once you have LOX production on the Moon, it’s not too hard to upgrade for making hydrolox. It’s mostly the same equipment. And once you have hydrolox production, you’re just one reactor short of methalox production. You need to react the hydrogen with carbon to make methane; the rest of the equipment is the same.

    If you want to get more fancy, you can react the carbon with water first, to get syngas, and then run that through Sabatier. That should also work better with asteroidal carbon. But it’s more complicated, so can be done later.

    Handling the carbon shouldn’t be too different from handling regolith, which isn’t straightforward, but you’d need to do that anyway to make LOX or hydrolox. In theory, by my calculations, a single fully refueled BFS should be able to land all the equipment necessary to start methalox production, plus enough carbon for the return trip. But it might take a while to make enough methalox to send it back.

    Reply
  31. Increasing the methane pressure would push its melting point higher, but you could compensate by increasing the oxygen pressure some more. So yes, that should work. Good point.

    Reply
  32. The big differences: 1) Lifetime of the propellant on-orbit. Xenon can be stored for years. Cryogenics can currently be stored for hours. The technology needs to be matured to get that up to at least weeks. 2) Volume transferred. For servicing birds with electric thrusters, you’re talking about transferring a few kg. The PPE for the LOP is talking about a couple of tonnes. But you’d have to transfer tens of tonnes to do on-orbit cryogenic refueling. 3) I’m on thin ice on this one, but your mating systems, connectors, and piping are going to be a lot easier at 165 K for Xenon than they are at 90 K for LOX, 111 K for LCH4, or 20 K for LH2.

    Reply
  33. The big differences:1) Lifetime of the propellant on-orbit. Xenon can be stored for years. Cryogenics can currently be stored for hours. The technology needs to be matured to get that up to at least weeks.2) Volume transferred. For servicing birds with electric thrusters you’re talking about transferring a few kg. The PPE for the LOP is talking about a couple of tonnes. But you’d have to transfer tens of tonnes to do on-orbit cryogenic refueling.3) I’m on thin ice on this one but your mating systems connectors and piping are going to be a lot easier at 165 K for Xenon than they are at 90 K for LOX 111 K for LCH4 or 20 K for LH2.

    Reply
  34. I don’t think there are any insurmountable problems with cryogenic refueling, but there’s a huge amount of technology readiness work that needs to be done.

    One example: You’d like to be able to reuse the same cryo couplers that you fill/drain the vehicle on the pad once you’re in space, but the T-0 breakaways don’t currently allow that. Here (http://www.altius-space.com/cryo-coupler-sbir-phase-ii-win/ ) is a company that’s working on developing a common cryo coupler.

    Other things: Orbital rendezvous for prop depots isn’t exactly straightforward, because you have to make the prop depot orbital elements compatible with the BEO departure orbit. There’s some work that’s being done in this area, but it’s quite likely that a long-dwell depot won’t be possible first time out of the chute.

    Then there’s the whole issue of allowing heat into the system through the docking and coupling mechanisms, as well as managing power to the depot without warming it up. You’ve got issues surrounding ground radiation if you want to do refueling on the Moon, along with making the whole system safe in the presence of lunar dust.

    Finally, note that, while methane is awesome if you’re launching it from Earth, it’s not possible to manufacture it on the lunar surface without a source of carbon. So there are lots of logistical problems associated with developing either a mixed methane/hydrogen propellant economy, or in delivering a carbon source to the Moon.

    Bottom line: As with everything else that has to do with space, getting the technology to be ready is about two orders of magnitude more work than developing the conceptual architecture. That’s why it would be nice to see NASA get serious about it. But I’m not holding my breath.

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  35. Not really my area but I suspect that 90% of the tech developed to transfer xenon propellant would be directly applicable to transferring other fluids.

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  36. Not really my area but I suspect that 90{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of the tech developed to transfer xenon propellant would be directly applicable to transferring other fluids.

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  37. That’s most likely exactly it. There are already trade studies done for optimal locations per architecture setup, even getting down to the detail of “lunar surface gas station fueled by ISRU” vs. lunar orbital depot vs. GEO depot vs. L2 depot and all the delta-V’s inbetween, which would degrade the desire for SLS.

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  38. That’s most likely exactly it. There are already trade studies done for optimal locations per architecture setup even getting down to the detail of lunar surface gas station fueled by ISRU”” vs. lunar orbital depot vs. GEO depot vs. L2 depot and all the delta-V’s inbetween”””” which would degrade the desire for SLS.”””

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  39. For the storage part, I would guess that a good solar shade should be enough to minimize methane and LOX evaporation, since space is pretty cold in the shadows. You’d still need the right tank materials, but we have experience with LNG and LOX tanks down here on Earth. The inner lining and overall structure would likely be similar, but you may want lighter structural and insulation materials and some extra layers on the outside. The experience from ISS and heatshields may be applicable.

    It should be possible to store and transfer LOX and methane at nearly the same temperature, with some insulation between them, since oxygen’s boiling point and methane’s melting point are both near 90K. Unfortunately, methane’s melting point is just a bit higher, and you don’t want the methane to freeze or the oxygen to boil, so you’d need to keep the oxygen at a slightly lower temperature. Maybe it’s possible to mix in a small fraction of some other gas (hydrogen? propane?) to get these temperatures to overlap. Either way, one could probably design a single system for a common temperature range, which saves some on engineering.

    Hydrogen is quite a bit harder on all counts, which is part of why SpaceX chose methalox.

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  40. It sure would be nice to see NASA get serious about on-orbit cryogenic propellant transfer. Electric propellant is all well and good for satellite servicing, but it’s not going to get you tens of tonnes of payload to the lunar or martian surface. Of course, that’s exactly why they’re [i]not[/i] pursuing it. Anything that would undermine SLS isn’t going to be tolerated.

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  41. It sure would be nice to see NASA get serious about on-orbit cryogenic propellant transfer. Electric propellant is all well and good for satellite servicing but it’s not going to get you tens of tonnes of payload to the lunar or martian surface.Of course that’s exactly why they’re [i]not[/i] pursuing it. Anything that would undermine SLS isn’t going to be tolerated.

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  42. The big differences:

    1) Lifetime of the propellant on-orbit. Xenon can be stored for years. Cryogenics can currently be stored for hours. The technology needs to be matured to get that up to at least weeks.

    2) Volume transferred. For servicing birds with electric thrusters, you’re talking about transferring a few kg. The PPE for the LOP is talking about a couple of tonnes. But you’d have to transfer tens of tonnes to do on-orbit cryogenic refueling.

    3) I’m on thin ice on this one, but your mating systems, connectors, and piping are going to be a lot easier at 165 K for Xenon than they are at 90 K for LOX, 111 K for LCH4, or 20 K for LH2.

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  43. That’s most likely exactly it. There are already trade studies done for optimal locations per architecture setup, even getting down to the detail of “lunar surface gas station fueled by ISRU” vs. lunar orbital depot vs. GEO depot vs. L2 depot and all the delta-V’s inbetween, which would degrade the desire for SLS.

    Reply
  44. It sure would be nice to see NASA get serious about on-orbit cryogenic propellant transfer. Electric propellant is all well and good for satellite servicing, but it’s not going to get you tens of tonnes of payload to the lunar or martian surface.

    Of course, that’s exactly why they’re [i]not[/i] pursuing it. Anything that would undermine SLS isn’t going to be tolerated.

    Reply

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