Chair Force Engineer

Friday, April 16, 2010

Rescue Me

The Orion spacecraft, in some form, will survive as a Crew Rescue Vehicle for the International Space Station. The new CRV program may prove to be little more than a NASA make-work program, as the need for a CRV is low. I see two scenarios where CRV might be used. The first is an incident such as the Mir fire of 1996 or Mir-Progress collision of 1997 which makes ISS uninhabitable. The other is a medical emergency that forces the evacuation of a crewmember from the ISS.

The success of a CRV is dependent on how quickly it can evacuate a crew from the ISS back to earth. Time may be working against the CRV. In the case of a capsule like Soyuz, a recovery crew needs to be dispatched to the targeted landing zone to recover the crew and capsule in helicopters. A good question (which I don't have an answer for right now) is whether the Russians currently keep a recovery force on standby at all times in the event that ISS was evacuated on short notice. It would certainly be necessary if anytime-evacuation of ISS was required.

The method of landing also impacts the speed in which a sick crewmember could receive medical attention. The runway landing approach used by X-38 would get the crew close to a hospital immediately after the CRV was landed and safed. On the other hand, an ocean splashdown would require a long time to mobilize (depending on the recovery ships that were chosen.) Conceivably one of the recovery ships would be a US Navy vessel outfitted with medical facilities. The Soyuz-style land recovery would require administration of first-aid aboard the helicopter while the crewmember was flown to a hospital.

The sick crewmember scenario is not the best one for a CRV, because it presupposes that 1) the illness or injury is grave enough to force evacuation, yet does not require immediate treatment, and 2) the entire crew should be evacuated because one member is in grave condition. A capsule of Orion's size would be a waste in this scenario. A better approach would evacuate the sick crewmember and two other astronauts in the capsule that they originally arrived in (either Soyuz, Dragon, or another commercial alternative.) A second capsule would be available to the remaining three crew as they continued their mission.

The best case for using an Orion lifeboat is a space station failure that allows for enough time to evacuate the crew to a CRV. I suspect that most mission-ending failures at the space station would be catastrophic and quick, resulting in the loss of all crew. But assuming a scenario like rapid loss of electrical power or life support systems, it is nice to have a backup spacecraft that could undock and even operate as a free-flyer for a short period of time before returning to earth. Again, the difficulty lies in arguing that developing a large six-man spacecraft is necessary when two three-man spacecraft will already be docked to the ISS.

In resurrected form, Orion still begs questions of which launcher will carry it into orbit. In a stripped form that will only fly to ISS and back (and assuming the size is not reduced,) it will likely be light enough to launch on a Delta IV Heavy. Shrinking the diameter might make it compatible with the existing Atlas V variants. By launching with no crew aboard, the traditional arguments about "human rating" requirements are void.