2) The Dagon capsule looks a lot like it could be developed into a manned spacecraft. But the version that will demonstrate initial cargo capacity will probably be a much less capable vehicle than existing manned spacecraft. For meeting NASA’s demonstration COTS cargo goals a launcher with 70% reliability going up and a reentry capsule with 80% going down, no life support in transit, and no launch abort system is perfectly adequate.

3) However, by the standards of existing manned spacecraft, this is grossly inadequate. The Russians are happy to sell seats on their venerable Soyuz. This has a historical reliability of about 97% going up, 98% going down, and a launch abort system that could allow the crew to survive a launch failure more often than not. Actual reentry reliability is probably better than that: the only fatalities were very early in the program, although there have been close calls since.

4) Reliable and safe life support isn’t a trivial problem. Just ask the crews of Apollo 1 and 13 and Soyuz 11.

5) Dragon could evolve into a cost effective manned spacecraft. Unfortunately, the most economical way to do this is to spend a decade or two as a profitable unmanned cargo vehicle finding and eliminating failure modes in the capsule and launcher. This is not a good quick solution to the gap in US manned spaceflight capability after the Shuttle retires.

6) If I was running NASA and Congress gave me an extra billion dollars earmarked for shortening the gap between Shuttle retirement and a useful operational US manned orbital spacecraft, I would not spend it on a manned Dragon capsule on an as yet unflown Falcon 9 built by a team that has yet to get Falcon 1 to orbit. Instead I would concentrate on an interim Orion spacecraft with only enough propellant and tankage to reliably get to ISS, flying on a Delta IV-H. “Man-rating” for the interim launcher would concentrate on detecting faults where a manned capsule would want to abort immediately but an unmanned payload would stay with the launcher and hope for the best.

7) I don’t think Congress will give NASA anything like a billion dollars to achieve that goal. Congress would rather have US astronauts flying in US spacecraft rather than Russian ones a few years sooner, but they probably won’t pay a billion dollars for the pleasure.

But again, I think that even if you think that COTS is much more likely to fail than Ares-I/Orion, I think the math still points to putting more funding into COTS. COTS is a high risk, low-cost, high reward option (where a little extra money can go a long way). Ares-I/Orion is a moderate risk, high cost, low reward option (where even a ton of money only goes a short way).

~Jon

I think you could make a much more persuasive argument for more COTS funding if one of the contenders had actually built and flown something.

The Soyuz, Progress, and ATV all dock through the small Russian port, and any cargo in them has to go through that port.

True, but HTV and both of the US COTS approaches use the CBM, which should allow for the maximum size internal cargo.

Also, the Space Shuttle carries really big unpressurized things, of course.

Yeah, it was the unpressurized cargo that I was wondering about. I don’t know if Progress, ATV, or HTV have the capability to fly the remaining needed unpressurized cargo or not. Or if those would have to fly on COTS.

If I understand correctly, you can’t just boost a space station module up on an Atlas V, because you need to manuever the module to within grappling distance and delta-V of the Canadarm, you need to provide structure around the module during launch, and you need to dissassociate from the module, without bonking the ISS.

But none of the COTS vehicles are designed to deliver space station modules either. I’m not sure what your point is there.

I know that Dragon has an unpressurized option. How big an object can they get up there?

Not a space station module, I can tell you that. However I don’t have the exact numbers. What I was trying to find out was if any of the existing or nearterm cargo haulers could deliver unpressurized cargo big enough to handle the largest remaining pieces. Ie are Dragon and Cygnus really delivering entirely new and critical capability? Or is NASA focusing its funding on a largely redundant cargo role instead of the more critical manned transport in order to avoid attracting extra funding that could be thrown down the Ares-I/Orion hole?

~Jon

The Soyuz, Progress, and ATV all dock through the small Russian port, and any cargo in them has to go through that port.

The Space Shuttle uses the larger American port, so larger pressurized cargo can go through that. Also, the Space Shuttle carries really big unpressurized things, of course.

If I understand correctly, you can’t just boost a space station module up on an Atlas V, because you need to manuever the module to within grappling distance and delta-V of the Canadarm, you need to provide structure around the module during launch, and you need to dissassociate from the module, without bonking the ISS.

I know that Dragon has an unpressurized option. How big an object can they get up there?