Still, Mr. Lyles said there would be no need for a full-scale redesign. Additional analysis has indicated the problem is not as severe as first thought, and the two vibrational frequencies may turn out to be far enough apart, more than 10 percent, that nothing needs to be changed at all.Why is this a problem, you ask? Observe this video of the Tacoma Narrows Bridge. Since 1940 this bridge has been an object lesson to engineers of all stripes. It is inconceivable that the engineers at NASA are not aware of this bridge and the issue of resonant frequency. It is further inconceivable that they would assume that a ten percent difference in the resonant frequencies of the solid rocket booster and the second stage would be enough to save them from the same fate as Galloping Gertie.
If fixes are necessary, rocket scientists know what to do. A shock absorber could be added between the first and second stages, or the structure could be modified to change the resonance frequency.
It is not trivial to change the Ares rocket to eliminate the resonance caused by the natural operating frequency of the solid rocket booster. The shuttle gets away with it because its 4-stage solid rockets are attached at top and bottom to the side of the external fuel tank, which acts as a strongback for the shuttle stack and dampens the vibrations from the SRBs due both to the strength of the materials of the tank and the dual connection points. On the Ares, the second stage is balanced atop a brand new 5-stage solid rocket booster; there really is only one attachment point, a ring at the top of the solid rocket. To damp out the oscillation "by adding a shock absorber" means adding a lot of mass between the SRB and the second stage or (worse) an even larger mass between the second stage and the Orion crew module.
The Ares-1 is overweight as it is; NASA still has to cut a ton from the mass of Orion in order to get the Ares off the pad, even though most of the weight of the safety systems has already been stripped from the design. In some cases the safety systems are single-string. That's brittle design - a single failure equals disaster.
The other option is to modify the design of the rocket to change the resonant frequency. The problem is that such a resonance is inherent to the design of any solid rocket booster. As the New York Times article points out, an SRB is like a pipe in a pipe organ. As the fuel burns, what remains behind is a hollow tube with a lot of air moving through it. No matter what solid rocket booster design NASA goes with, they still have the same issue of a resonant frequency. If they change the booster significantly (and many engineers would argue that adding a fifth segment to the booster is already a huge change), then they end up with completely different hardware than was used on the space shuttle; in other words, an entirely new, untested rocket, with no commonality to the existing shuttle system.
When Wernher von Braun put astronauts atop the Saturn V rockets, he wasn't guessing that the system would work. Every component and subsystem was thoroughly tested beforehand. With the Ares-1, they have eliminated much of the testing under budget pressure and the assumption that it is all legacy hardware from the shuttle system. Any redesigns to change the resonant frequency of the "Stick" will mean that they basically have to start over with a clean sheet (negating the efforts of the past three years and pushing back the first launch of Ares by that much) and test all components of the system as well as all subsystems (adding more dollars and years to the project). This is the very "full-scale redesign" that Garry Lyles of NASA's Marshall Space Flight Center dismisses out of hand.
There are other solutions, of course. For the upcoming moon missions, there will be two launches per mission: one Ares-V to launch the bulk of the hardware and fuel, and one Ares-1 for the crew. If instead the mass of the launches are divided up into two nearly-identical rockets midway in size between Ares-1 and Ares-V, then NASA can avoid the resonance issue by having two SRBs attached top-and-bottom to the sides of the strongback of the rocket and develop one rocket instead of two, using far more legacy (spaceflight tested) hardware. This is the essence of the DIRECT 2.0 proposal.
Another approach is to ensure and even expand the funding for the Commercial Orbital Transportation System teams. In comparison to the vaporware produced so far by NASA on the Ares, SpaceX has actually produced - from a standing start - two new rocket engines, and already started doing test flights. They have spent over the last five years about what NASA spends every eleven days. That's cost effective. Assuming NASA does not choke off COTS, then at the very least SpaceX will beat the Ares to orbit - and they may do so even if NASA kills COTS in the cradle. If that happens, then there will be no need whatsoever for Ares, and NASA will have wasted billions of dollars and years of effort for no actual results at all. And, if NASA assures funding for or even expands COTS, then there will be more than just SpaceX ready to provide rides to orbit for NASA astronauts.
Yet another approach is for NASA to actually do what it is supposed to do as a government agency - develop technologies that are not yet commercially viable but which lead to infrastructure improvements that make space access easier and more economical for everyone. Jon Goff has already written a lot about that, particularly about orbital propellant transfer and other technologies necessary for a spacefaring society.
And finally, NASA can go with existing launch systems like the Delta or Atlas. So what if they are not "man rated"? As Rand Simberg has pointed out many times, that qualification is artificial and not one of the rockets that NASA has ever used to fly men into space has ever met that qualification - "man rating" is simply a cudgel used by NASA as part of the not invented here syndrome.
For NASA, relying on hope that the system will work simply isn't good enough. Wishful thinking is no substitute for good engineering practice.
It is time for NASA to realize that the definition of "hindsight" does not include "inserting one's head in a very uncomfortable place". The Ares-1 "Stick" may be Mike Griffin's pet project, but that doesn't mean that its obvious shortcomings can be ignored any longer.
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