Chair Force Engineer

Saturday, April 25, 2009

Test like you fly

In the business of aerospace, the phrase "test as you fly" can never be repeated too often. All hardware should be tested on the ground in as realistic fashion as possible. Flight testing should come as close to the environments where the hardware will be flown. Traditionally, new rocket designs have been tested one stage at a time, using dummy upper stages. Why then would NASA reject this test strategy for Ares I?

Perhaps it's because Project Apollo abandoned incremental testing in favor of all-up testing. Nowhere was this more pronounced than Apollo 4, the first Saturn V flight, which was the first instance when the S-IC and S-II stages had ever flown before. Of course, NASA and its contractors had extensively tested the stages on the ground before, and S-IVB had been tested on Saturn IB launches. Project Apollo is often held up as a model for how a space program should be conducted, but it's really an exception rather than the rule. Apollo was the unique product of its circumstances, and its "crash the schedule" approach should not be viewed as standard industry practice.

The current Ares test schedule calls for Ares I-X this year, a test of a 4-segment SRB with a dummy fifth segment, dummy upper stage, and avionics that don't represent Ares flight avionics. The next step is Ares I-Y in 2012. I-Y will be the first flight of the real Ares I SRB, plus an inert upper stage that, minus the engine, resembles the real Ares I upper stage. Ares I-Y will also test the Orion escape system.

As I've said many times before, Ares I-X has little to no bearing on the Ares I flight hardware and should be terminated. Ares I-Y is a far better test because it does involve Ares flight hardware, but I'm not certain there's much to be gained from flying an engine-less second stage in place of a dummy upper stage.

Recently there's been talk of an "Ares I-X Prime" which would actually test a five-segment SRB with dummy upper stage. Now we're actually getting serious about "testing like we fly." This is what Ares I-X should have looked like all along. The problem with the "Prime" test flight, in my view, is that it's being considered as a replacement for Ares I-Y instead of Ares I-X.

At this point, Ares I-X doesn't really buy NASA anything, aside from positive PR if it works correctly. Ares I-Y isn't doing much more than Ares I-X Prime would do, aside from testing the supper stage structure under flight loads and allowing for the high-altitude abort test. A wiser and more fiscally-responsible strategy would be cancelling both Ares I-X and Ares I-Y, skipping ahead to Ares I-X Prime, and then making Orion 1 (the first in-flight ignition of the upper strage and first on-orbit test of the Orion spacecraft) the last test flight before humans fly on Ares-Orion.