Two serious blows were struck against the Senate Launch System this week, though based on previous behavior, when knocked down by reality, its supporters on the Hill will probably just pick themselves up, dust themselves off and continue to trot on foolishly as though nothing had happened.
First, over the weekend, on the editorial page of the Houston Chronicle, legendary NASA mission controller Chris Kraft told the Texas delegation that Houston has a problem:
The current national human exploration strategy, which is based on development of the SLS, is economically unaffordable. The SLS-based strategy is unaffordable, by definition, since the costs of developing, let alone operating, the SLS within a fixed or declining budget has crowded out funding for critical elements needed for any real deep space human exploration program. Most of these critical elements would be managed by JSC. They include the crewed lunar lander, a multi-mission space exploration vehicle (MMSEV), a deep space habitat, a lunar surface rover and other lunar infrastructure. The development of these critical elements has been delayed until the mid-2020s and the 2030s, so real human exploration beyond Earth will not begin until the late 2020s or 2030s.
This is not only politically unsustainable - it is technically unsustainable.
...SLS is killing JSC. SLS is killing Texas jobs. SLS is killing our national space agenda.
Emphasis mine. Not-so-subtle message to (Texas) Senator Kay Bailey Hutchison and Ralph Hall (R-Texas, Houston area), Chairman of the House Science, Space and Technology Committee, among others though he doesn't call any of them by name: "You're killing us here."
Of course, he's not complaining about pork, per se, but rather that, in supporting the giant rocket with no missions, the Texas delegation is sending it to the wrong states and districts. But given the respect in the space community for him (and his co-author, former space station director Tom Moser), attention may be paid.
But then came the second hit.
For years, ever since the heavy-lift Ares was perceived to be in trouble before Constellation was canceled, proponents of it (and later SLS) have tried to sow Fear, Uncertainty and Doubt (FUD™) by claiming that avoiding the use of a heavy-lift vehicle by utilizing orbital assembly and propellant depots was too complex and hazardous, insisting on the tried and true Apollo way, in which everything was launched on a giant rocket. "Requiring so many launches to do a mission dramatically increases the probability of mission failure," they said, "because any launch failure will doom the mission, and the joint probability of getting them all off on schedule without a hitch is very low."
Even the NASA administrator made this argument in a congressional hearing last summer:
...in the ongoing evaluation that I asked in coming to the conclusion that I did on the SLS, we looked at multiple scenarios, one of which was, you know, flight to Earth orbit or what we call an "Earth orbit rendezvous," and it turned out that that was not as economical nor as reliable as the single flight beyond Earth orbit rendezvous, the way that we envision it now.
This was the politically correct answer, and the one that much of the committee, though probably not Congressman Rohrabacher, wanted to hear, because it bolstered the case for Shuttlyndra.
The argument was nonsense, of course, because it contained the implicit assumption that every single flight was mission critical. But in reality, most of the flights necessary for the mission would be propellant deliveries (the vast majority of the gross lift-off weight of the seven-million-pound Saturn V was the propellant needed to get the little crew capsule all the way to the moon and back). Propellant is cheap, and if a propellant flight failed, it could be quickly replaced by another, perhaps from an alternative competitive commercial provider, or even international partner. And with the use of the propellant depots in various locations, including the lunar surface, in-space vehicles, such as transports to and from the moon, or lunar landers, can be reused, and only need to be launched once. The worst case of a launch failure would be of a mission delay, not a mission loss.
On the other hand, the solution of the Apollo cargo cultists puts all of the mission eggs in a single basket, so in the event of a rocket failure of the SLS, billions would be lost in an instant. This is one of the reasons that Apollo was canceled -- senior officials thought it just a matter of time before there was such a catastrophic failure. In fact we were very lucky, not to take anything away from the brilliant actions of people like Gene Kranz and Glynn Lunney, and yes, Chris Kraft himself -- contrary to the impression given by the popular movie, the flight directors worked in shifts -- to get the crew of Apollo 13 back.
Up until now, the argument has been largely qualitative, as described above. But Monday, a leaked NASA document, generated in November by the Safety and Mission Assurance (S&MA) office at the Johnson Space Center in Houston, put numbers to the argument, and said that the reality was that a depot-based solution actually reduced risk of loss of both missions and crew:
This study does not support the perception that depots add an unacceptable level of risk and should not be considered due to the increased number of launches, AR&Ds, and transfers...
Emphasis mine. Specifically, they describe how it actually improves things, and quantify it. They conclude:
...From the standpoint of S&MA's role in technology assessment and prioritization, it seems depot technologies should be a high priority for investment due to their potential to achieve Agency goals to achieve "Low Cost Reliable Access To Space," if the technology can be successfully developed, demonstrated, matured, infused, evolved, and applied in future architectures so as to fully realize its benefit.
Of course, they not only bury the lede, but leave it out completely, failing to point out that in addition to reducing costs and improving safety and reliability, it eliminates the need for the SLS, or any vehicle in its lift class. That still remains politically incorrect for current NASA employees to write, even in internal documents. But combine this result with the retired NASA veterans' weekend editorial, and it grows increasingly harder by the day to justify the billions being spent on this boondoggle, making it an ever-growing target in any coming cuts to the agency's budget.