At 03:46 AM 1/6/2003 -0500, you wrote:
We are going to launch them eyes-out-- their back is on the top bulkhead in the nosecone. This is probably going to be a controversial point in our design, but there is some good reasoning to it.You're going to land someone eyes-down?Dan
Reentry acceleration is briefly around 5G, and we are planning for landing impact to be 10G very briefly, while the burn time acceleration will be under 3G, so we want them oriented with their backs down on the way down.
We were designing for parachutes-in-the-nosecone, which would allow us to have all accelerations the same direction, but there are several difficulties with that. It is troublesome and heavy to have some form of landing attenuator on the base that will have a long enough stroke for parachute landing, and still keep the engines off the ground. It was also a worry that the cabin was over 20' above the ground, which could get slammed down pretty hard if the parachute deflates before the vehicle tips over. The top of a 10 degree nosecone isn't good for much else, but it makes for a very nice, long-stroke impact attenuator, and it puts the cabin basically at ground level after coming down on rear-mounted parachutes.
Especially with the desire to tailor the burn trajectory so that burnout is at a very low dynamic pressure for an unstable vehicle, the launch accelerations don't get all that high. Hanging from a harness (with hand grips and knee-rests) at 2-3G isn't going to be tons of fun, but it isn't even close to the voluntary limits listed in bioastronautics.
Our two other "passengers" are oriented the opposite way, which would probably hurt on landing, but it is still within the guidelines supported by research, and the vehicle will never fly with real people there. This is somewhat going against the spirit of the X-Prize rules, but it should still qualify. AST has made it clear that they will frown on any launch application that intends to actually fly three people for the X-Prize. We don't expect our X-Prize vehicle to be used for commercial space tourism, we plan to build another vehicle incorporating the lessons learned.
John Carmack
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