Crew and Cargo

Dan Schrimpsher pointed out in comments to my monculture post one of the interesting ideas that has gained a little too much traction lately at NASA–the importance of not having cargo and crew on the same vehicle. Apparently, most people now believe that one of the big reasons why Shuttle is so expensive is that it tries to be both a delivery truck and a passenger van. While there is some real grain of truth in that idea, I think it is missing a subtle point that I’ll try to explain below.

The technical problem I see with the shuttle isn’t that it combines crew and cargo per se. The technical problem that I see with the Shuttle is that it tries to be an earth-to-orbit crew transport, while simultaneously trying to be a heavy lift cargo vehicle while simultaneously trying to be a science lab, while simultaneously trying to be a space motel, not that it has both crew and cargo onboard. Most other manned vehicles to date have also carried some cargo. Soyuz carries several hundred pounds of cargo, Apollo did too. I’m not sure about Gemini, but imagine it had the capability. The ability to bring some cargo with crew is important, a Toyota without a trunk would be a relatively useless vehicle.

In fact, to me, a cargo delivery ship is begging to have at least two or three crew members on board to make the whole thing simpler–automated deployment of satellites without any people there to help is a major expense in the design of satellites for example. Cargo jets do fairly well mixing cargo and a little bit of crew, while passenger jets do well with lots of passengers and a little bit of cargo. I think it’s when you try to combine large amounts of crew, huge amounts of cargo, and long-term habitation facilities into a vehicle that it starts getting bloated.

Another part of this belief in a separation between cargo and crew is the belief that a crewed vehicle needs a higher safety level than a vehicle that is just for hauling cargo. I’m not sure how true this really is. How much happier would the people underwriting satellite launch insurance be if they knew that even in a bad situation the satellite will probably land intact and just be launched again? Guess what, when insurers are happier, eventually they start charging lower premiums. Who really would want to fly their expensive satellite on a vehicle whose designers wouldn’t trust flying themselves on? There isn’t much of alternative now, but that speaks more to the immaturity and lack of alternatives in the current launch industry than anything else. Whatever you’re flying, the ability to do an intact abort with the full cargo and crew complement (and the vehicle too if possible) is really important to actually making a profit in this field.

There are some additional nuances to be mentioned, but I think that I’ve said enough to make my point here.

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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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4 Responses to Crew and Cargo

  1. Kelly Starks says:

    Hi, I was in the shuttle program for several years and NASA for 15, and the costs had nothing really to do with any of the factors you and others assume. Shuttle was just a rushed job and a massive labor hog to service. In tests in the DC-X program they found fairly obvious design changes (repositioning equipment and adding access hatches, making all the rockets use the same fuel, hardened hull skins, etc) drop servicing costs for a shuttle sized craft about $300,000,000 per launch. Eliminate the $50,000,000 ET drop tank and do some bureaucratic house cleaning in addition to the above design mods, and your cost per launch drops by a factor of 10-20 or more.

  2. Kelly Starks says:

    PS Big agree with your point that the crew vrs cargo argument is dumb. We need passenger AND cargo launchers that give you significantly better survival rates then a WW-II B-17 trying to bomb Berlin without fighter escort. I mean our not being up to DC-10 levels of relyability is understandable – but can’t we get up to DC-3 levels??

  3. Jon Goff says:

    Kelly,

    Yes I was oversimplifying things a bit, but I think that the causes you are mentioning were directly related to decisions made early in the STS program. For instance, the decision that the vehicle needed to be able to carry 65klb to LEO and that it be able to do a once around landing. This pushed the size of the orbiter far larger than had originally been intended, and also required a much higher L/D design. Both of these made a fully reusable TSTO very expensive. When they decided to go with an ET drop tank, it made the orbiter a lot smaller volume wise, but a lot denser on reentry. With the much higher ballistic coefficient and the high required L/D for the once-around requirement, the TPS system required using ceramic tiles instead of lower-maintenance TPS solutions. The booster rockets must have seemed like a better idea at the time than what would have now been a massive first stage. And the work platforms and extra access panels were cut due to weight overruns. Lastly, the RCS engines which were originally going to be GOX/GH2 were switched to hypergolic based thrusters that were considered lower cost and technical risk.

    In addition to that you faced a lot of the same pressures that are going on right now with shuttle retirement. In order to maintain political support, NASA wanted to keep as many former Apollo engineers busy as possible, so requiring the use of the VAB for shuttle work was just an added bonus.

    All that said, if they had gone with a more reasonable design, say one with 10-15klb of cargo, and less long duration habitation facilities, I think the reduced size of the system would have allowed for a reasonably doable reusable first stage. With this being NASA I doubt it would have been truly CATS, but it would’ve been a lot better.

    As for the reliability comment, yeah even 98% reliability is (or should darn well be) unacceptably poor for manned or unmanned launches.

  4. Kelly Starks says:

    I thought the denser orbiter was needed for the higher entry speeds the cross range needed?

    In any sence none of what you listed (lack of a flyback first stage, ET, cross range, size) had any real input on the huge costs per flight. Well except for the fragile TPS, but the current design wasn’t the only way to do it, and it was required more for the aluminum hull (which was dumb) then any real lack of alternatives.

    For grins I worked up a back of the envelop “refit” concept for shuttle where the orbiters get stretched about 10 m, refitted with RD-180s and internal fuel tanks and launched as a two orbiter “biamese” config. I.E. you get a fly back first stage, but it’s just a duplicate orbiter pulling tug duty that day. So there is no cost to develop a second class of stage.

    Glad we agree about reliability. It’s really getting scary how casually folks rattle off the “well space flight is intrinsically dangerous” line. Hell armed combat and airliners are intrinsically dangerous – but we don’t tolerate anything like these loss rates in eiather field for normal ops. Its bad when shuttle astrounauts would be safer with the Marines taking Faluga, then flying cargo to the ISS!

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