As first reported by the Associated Press and the Web site NASAwatch.com, computer simulations have shown that the Ares 1, which is based on the solid-rocket motors used to boost NASA’s space shuttle into orbit, has a thrust oscillation issue that could cause unacceptable levels of vibration during flight.
The problem must be deemed serious since, if not corrected, it could result in damage to or even the loss of the Orion Crew Exploration Vehicle that will launch atop Ares. However, the scheduled debut of those vehicles is still seven years away; NASA engineers have plenty of time to correct the problem, if in fact it is as serious as the simulations have indicated.
NASA Administrator Mike Griffin faced questions about the matter following a long-scheduled speech Jan. 22 in Washington in which he outlined the reasoning behind the agency’s choices of hardware for returning to the Moon, among them a shuttle-derived launcher. Many of those
in attendance wanted to know not only the gravity of the problem, which was discovered in October, but also why it was not revealed publicly until a Freedom of Information Act request forced the agency’s hand.
It turns out that NASA notified the relevant congressional staff not long after it became aware of the potential issue. Mr. Griffin and other NASA officials also made clear that they do not believe the problem is that big a deal.
That remains to be seen, of course, but these officials are not completely unjustified in their optimism. In the first place, as Mr. Griffin pointed out, further analysis is needed to verify that there is indeed a problem. There have been incidents in the recent past – one involving the Ares 1’s J-2 second-stage engine – where indications of potential showstoppers have proven, upon further review, to be false.
Should the additional analysis determine that the thrust oscillation issue is in fact real and serious, NASA already has identified potential fixes ranging from changing the solid propellant load in the booster to an isolation system that dampens the effect of the vibrations on Orion. Thrust oscillation is a well-known phenomenon on solid-rocket motors, and NASA and its Ares 1 prime contractor, AlliantTechsystems, have a vast wealth of experience dealing with it.
Congress and the White House obviously need to keep close tabs on the situation, and NASA must be vigilant about keeping them apprised of all new developments – good or bad. But what this situation does not call for is a revisit of NASA’s chosen shuttle replacement and lunar exploration architecture.
NASA had sound reasons for selecting the shuttle-based Ares 1 launcher over an alternative derived from the Atlas 5 and Delta 4 rockets developed under the U.S. Air Force’s Evolved Expendable Launch Vehicle (EELV) program. The list includes NASA’s assessment that the shuttle-derived option would cost less to develop and operate, and that an EELV-based vehicle, while capable of launching Orion to the space station, is not well-suited for Moon-bound missions. To reconsider the EELV-based approach at the first sign of trouble on the Ar
es 1 program would be tantamount to preparing to abandon a ship in mid ocean at the first sign of a leak.
Thrust oscillation on Ares 1 could turn out to be a bigger challenge than NASA anticipates, but the good news is that it was identified early on in the program. As expert panels have noted, a major contributor to the development problems that have plagued space hardware programs over the last decade or so has been inadequate systems engineering during the design phase. This has allowed potential bugs to slip in undetected, only to manifest themselves during construction – with devastating programmatic consequences. In this instance, a bug was identified early; the system worked.
Obviously it cannot be known today whether the Ares 1 team has missed anything that will later come back to bite the program. But the early discovery of the thrust oscillation issue is an indication that NASA and its contractor are doing something right.