http://www.spacedaily.com/news/rocketscience-03zj1.html The End Of US Manned Spaceflight Looms Ever Closer The US manned space program has at best only a few more years of missions left in it, until its cost, complexity and design flaws results in another failure that grounds all US manned launches until a new transport system is designed and built.
by Jeffrey F. Bell Honolulu – Jul 10, 2003
Once again, NASA has proposed to develop a replacement for the troubled Space Shuttle. This year’s project goes by the ungrammatical moniker “Orbital Space Plane”. An interim version of OSP called the CRV (Crew Rescue Vehicle) to be developed by 2010 will take over the International Space Station lifeboat task now done by Soyuz.
An improved OSP called the CTV (Crew Transfer Vehicle) will assume the ISS crew exchange task now done by Shuttle in 2012. To minimize development costs, the OSP will be launched on one of the new EELV family of expendable boosters, Delta 4 or Atlas V.
Sound familiar? It should. The OSP is only the latest of many “Shuttle replacement” programs that have all failed dismally. A close look at OSP shows that this program is also doomed to failure due to fundamental technical defects. It’s no surprise that such usually reliable NASA boosters as “Space Coast” Congressman Dave Weldon and aerospace lobbyist Lori Garver have publicly attacked OSP.
Most critics have focused on the suspiciously low development costs, or the embarrassing gap between 2006 and 2010 in which no ISS lifeboat is planned. In fact, the basic concept of the program is so stupid that every knowledgeable person involved in it must be perfectly aware that it will never fly.
The basic problem is that the OSP, as currently defined, must carry such heavy mass penalties in the form of wings, wheels, and various escape systems that its performance will not be much better than the Dyna-Soar design of 40 years ago.
Because it cannot carry any of the supplies needed to sustain its passengers once they arrive at the ISS, it will not reduce the number or expense of Shuttle missions needed to support the International Space Station, and will not provide “assured access to space” as NASA claims.
Instead OSP will force NASA to simultaneously fly two very expensive man-rated vehicles at a time when it is financially unable to support even one, and will double the risk of long stand-downs in ISS operations due to lack of either replacement crewmen or the supplies needed to keep them alive.
The Shrinking Spaceplane Mystery: The original OSP concept envisioned a 7-seat vehicle which could rescue or exchange the entire ISS crew in one sortie. (NASA’s proposed Budget Amendment of 14 November ’02 said “as many as 10”.) The Level I requirement document reduced this to “at least 4” persons.
This major decline in the OSP’s basic performance measure was widely criticized. Although I have not seen an official justification for the 4-seat requirement, it appears to be based on an agreement among ISS users that NASA will be responsible for escape and exchange only of the non-Russian ISS crew members, with the RSA continuing to support 2 or 3 Russian crewpersons with 2-3 Soyuz TMA flights per year.
However, a later NASA document “interpreting” the Level I requirements ( online reference ) has gone mostly unnoticed. In this ‘interpretation” the requirement for “at least 4” seats in OSP has been changed to a “system requirement” that can be reached using multiple spacecraft instead of only one! Presumably, proposals for 2-seat or even 1-seat spacecraft would be now considered acceptable under this bizarre “interpretation” of the “at least 4” requirement.
I know of no other aerospace program in which the basic performance goal has been lowered by a factor of FOUR in the first few months! This isn’t just a question of being “a step backward from Shuttle” (or even from Soyuz), but fundamentally wrecks the economics of the program. Even in the CRV mode, a 2-seat OSP is an extremely dubious proposition.
The normal configuration of the station would then be one in which two OSPs and a Soyuz would occupy three docking ports, oriented in such a way that all three lifeboats could be manned and pull away from the Station in any desired order, while leaving other ports free for CTV or supply vehicle docking.
In the CTV mode, the 2-seat OSP would be heavily burdened by the irreducible overhead of basic nav, comm, and docking equipment that cannot be scaled down. So by cutting the seating in half, NASA has much more than doubled the annual cost of rotating ISS crews.
NASA has not given any reasons for this extraordinary lowering of the bar that the three competing contractor teams have to reach. The most likely explanation is that preliminary studies have revealed a 7-seat or 4-seat spaceplane turns out too heavy to be launched on Delta 4 or Atlas V, when all necessary requirements are met.
To see what kind of problems they may have found, let’s compare it with the previous, now-cancelled design for a 6-seat Station CRV, the X-38. The X-38 was very narrowly tailored for the CRV requirement. It lacked most of the systems needed for independent flight, since it was to be carried into orbit inside a Shuttle and docked to the ISS with the aid of the Canadarm2. The ECS supported 6 persons for only 9 hours, the RCS used compressed nitrogen, avionics were highly simplified, there was no rendezvous and docking gear, landing used a simple solid retrorocket, parachute and skids.
There was no question of reusability since it was an emergency lifeboat, and since it would only be used once or twice in the lifetime of ISS high reliability was unneeded.
Now let us imagine a CTV version of the X-38. Clearly, a lot of stuff needs to be added: radar, computers, control rockets, fuel, instrument panel, a window to look out of, a docking mechanism that can tolerate significant misalignments and shocks, more O2 and N2 tanks, more CO2 scrubbers, real thermal control, extra batteries.
Many of these systems need to be duplicated to provide sufficient reliability for routine flights, and everything needs to be reusable with minimal maintenance between flights. There just isn’t volume for this stuff in X-38 (or any winged vehicle of its approximate size and weight) without throwing out some of the seats.
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