Heavy lift: examining the requirements
by Taylor Dinerman
|The heavy-lift decision will shape the future of the whole exploration vision, just as the decision to build the shuttle determined the size and, to some extent, the nature of the ISS and of everything from the Hubble Space Telescope to the late Galileo Jupiter probe.|
Strict considerations of the cost efficiency of such a Very Heavy Launch Vehicle (VHLV) itself are not the only factors going into this decision. The US military is probably supporting the Delta 4, or possibly an Atlas 5, in order to reduce their costs. In Florida and elsewhere, people are pushing for a shuttle-derived system in order to save their jobs and to insure that the huge investment that the nation has made in the shuttle’s infrastructure does not get thrown away, as happened to the Saturn 5. If this comes down to a “under the covers” fight between parts of NASA and parts of DoD, the Pentagon will likely win, but only if the choice is defined in a fairly narrow way.
If the leadership of the DoD were to look out beyond the five-year budget planning cycle and the Quadrennial Defense Review, they would see that there is a strong possibility that there will be a need for a military VHLV, probably beginning in the middle of the next decade. Future space based sensors will require very large apertures, and the ultra-lightweight systems and materials which many experts hoped to see developed by then will just not be there. The power requirements of a future military laser communications satellite might also be much larger than expected.
There is also the question of future space weapons. The now-canceled Space Based Laser program would have required as much as five tons of chemicals per shot. In its full operational configuration, the whole thing would have weighed about eighty tons. While nothing like this is now on the drawing board, there are other possible uses for a heavy-lift vehicle. For example, small boost-phase intercept weapons, such as Brilliant Pebbles, could be launched in very large numbers, and all at once on such a rocket. So could very heavy kinetic energy strike weapons that could penetrate deeply buried targets without resorting to nuclear, or even chemical, explosives.
|If the leadership of the DoD were to look out beyond the five-year budget planning cycle and the Quadrennial Defense Review, they would see that there is a strong possibility that there will be a need for a military VHLV, probably beginning in the middle of the next decade.|
A heavy-lift launch system could be used to replace large numbers of military satellites that had been lost to a “Space Pearl Harbor” type attack. The fact that it could do so in a single launch, rather than after a long drawn out series of launch campaigns, should make this option attractive to US strategic planners trying to cope with future worst-case scenarios.
According to information supplied by Boeing for Craig Covault’s excellent article in the February 21st edition of Aviation Week, a highly evolved version of the Delta 4 could put a bit more than 50 tons into Low Earth Orbit (LEO). An extremely evolved version would be able to orbit as much as 85 tons. The need to man-rate at least one version of the Delta 4 is going to make for an expensive process, but at least the Boeing rocket has an infrastructure already in place.
The need to develop a cross-feed system so that fuel from all three tanks can be directed, or redirected, to the appropriate RS-68 engine, will be expensive, as will a highly refined new automated vehicle health monitoring system. However, such system and the other improvements planned for both the Delta 4 and Atlas 5, will improve their performance in both their military and commercial (if any) missions.
In the February 7th edition of Aviation Week, Frank Morning informs us that an in-line shuttle-derived vehicle could launch as much as one hundred tons to LEO. As with the Delta 4, the infrastructure is already in place, and there are plenty of trained people available. The modifications to the system are almost certainly far less than those needed to give the Boeing rocket an 85-ton-to-LEO capability. The difficulty with the shuttle-derived concepts is the idea that the CEV will be launched on top of a single modified Solid Rocket Booster (SRB). (See “CEV: a different approach”, The Space Review, September 13, 2004)
While the SRBs have had a pretty good safety record since the Challenger disaster, they are still inherently less safe than a liquid-fueled, and thus controllable, rocket. It has been proposed for both the Delta 4 Medium and for the SRB-derived CEV launch systems that they have an escape tower similar to the ones used on the Mercury, Gemini, and Apollo capsules. Such a tower will, in any case, be a part of any baseline CEV design. A manned system deserves a more robust, multilayered set of safeguards.
|The final decision on heavy lift is going to take some very careful thought. Most of the cost estimates that purport to say what funding will be needed ten years from now are not worth the paper they are written on.|
By the time the first CEV operational flight is launched around 2014, the shape of the launch market will probably have changed pretty radically. If Elon Musk’s Falcons work out, they will probably have taken a good deal of market share from the Delta 2 and, possibly, even from the smaller versions of the Delta 4 and Atlas 5. Other innovative launch vehicles might also have reached the market. The US military will probably be a big user of the heavy versions of the EELVs, and there will be a small, but regular, commercial demand for putting large satellites and structures into orbit.
The demand for VHLVs could be as much as three or four launches a year, including at least some purely military missions. If the cost can be controlled, the case for developing a shuttle-derived system is pretty good, but not if it is going to absorb anything like the same percentage of NASA’s budget as the Shuttle does now. The DoD probably does not see any missions on the horizon that require the capability to put 50 or 80 tons into LEO but, if that changes and the Shuttle infrastructure has been abandoned, they will be faced with some pretty unpleasant alternatives.
The final decision on heavy lift is going to take some very careful thought. Most of the cost estimates that purport to say what funding will be needed ten years from now are not worth the paper they are written on. Somebody in the US government is going to have to make an inspired guess, and the country will have to live with it for a very long time to come.