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| Re: GAO recommends against NASA's Ares I launcher (507416) | |||
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Re: GAO recommends against NASA's Ares I launcher |
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Posted by WillD on Wed Oct 7 00:18:10 2009, in response to Re: GAO recommends against NASA's Ares I launcher, posted by JohnL on Tue Oct 6 20:56:19 2009. I get the impression that the current Ares program is primarily designed to keep ATK in business making solid fuel boosters.Hit the nail on the head. It was basically a 10 billion dollar handout to Alliant Tech, partly because Orrin Hatch needed some pork, and partly because ATK only other real product is fuel for missiles. The Shuttle program's insatiable need for large quantities of aluminum perchlorate creates an enormous economy of scale for the DoD's weapons programs. The Ares V is even more pork, with very large contracts about to be let to Rocketdyne for RS-68R engine development and the Marshall Spaceflight Center's 10 meter core development project. We haven't even started talking about the Altair lunar lander, yet are facing the prospect that the entire budget will be consumed by the launch vehicles and capsule alone. I like the DIRECT idea. However, I would modify it by swapping as far as possible the SSMEs for RS-68s. The SSMEs are expensive, but they are reused. None of the DIRECT hardware is, so cheaper, one-use only parts should be substituted. The second iteration of the Direct launch vehicles (then called Ares II and III) included 2 and 3 RS-68 engines. Unfortunately in NASA's estimation the ablative design of the RS-68 would not stand up to the heating produced on the bottom of the first stage by the solid rocket boosters. The RS-68 is actually a more powerful engine than the SSME, but it sacrifices a bit of controllability and specific impulse for its lower cost and simplicity. The ablative nature of the RS-68 is the biggest stumbling block, with the rocket nozzle designed to slowly erode over the course of the flight. On the bottom of a Delta 4 rocket this isn't a problem because its a far more benign environment than being next to an SRB, which would erode it from the out while the RS-68 erodes itself from the inside. The SSME circulates liquid hydrogen through the exhaust bell throughout flight and is thus a regeneratively cooled engine immune to base heating problems. A regeneratively cooled RS-68 has been proposed, but it nearly amounts to a new rocket design. As yet NASA has not bothered to address the potential base heating problems of the Ares V, which should be far more severe than either of the Jupiter variants, with 5 or 6 RS-68s and two 5.5 segment SRBs clustered in the bottom. So far both the Direct advocates and advocates of the "Not Shuttle C" side-mount cargo carrier model are touting the fact that we'll have 17 SSMEs ready for flight after the Shuttle program ends. However, with both models eating through 3 or 4 every flight, that's only enough for 3 flights at most. The cost of an SSME is roughly 35 million dollars, while an RS-68 comes in at about 25 million dollars. Direct and NSC proponents claim that the Space Transportation Main Engine, a greatly simplified, cheaper LOX/LH2 engine based on the SSME, would cost less than 30 million dollars a pop and save time and money relative to developing a regenerative RS-68 engine. I suggested they investigate a drop-capsule to recover the rocket engines, something proposed for future Saturn V rockets that never developed, but was told that the cost of development would only be mitigated if they planned to fly on a nearly weekly basis. One thing I don’t understand, and I have never seen any references, is what does it take to human rate a launch vehicle? I have seen many articles citing the cost of uprating the Atlas/Titan/Centaur vehicles, but no-one seems to know what it entails. There are a huge number of things that go into it and I'm not sure of all of them. However, Air and Space magazine ran a piece on the man-rating of the SpaceX Falcon9/Dragon, and the Ares I/Orion not too long back. According to the article I believe the primary factor with respect to the launch vehicle man rating is both the probability of loss of crew and the probability of loss of mission, along with the path taken into orbit. The Shuttle stack gets a bit of a ding in the probability of loss of crew category because of the Challenger disaster. SpaceX's Falcon 9 achieves low LOC/LOM probability numbers through redundancy, with 9 engines in the first stage, any one of which can fail without scrubbing a mission. OTOH the Ares I's LOC/LOM probability is centered around supposedly proven hardware (although the J-2, having not flown for nearly 30 years, is hardly proven, especially after what they did to it to get the J-2X). LOC/LOM numbers can be reduced through modification of the path into orbit. Both the Orion and Dragon capsules are designed with an offset center of gravity, like the Apollo capsule. This allows them some control over pitch and yaw during reentry. Thus they become in essence very poor lifting body craft during reentry, and that allows them to remain in the thin upper atmosphere bleeding off speed more slowly than if they were to reenter with a purely ballistic trajectory. G loads are not supposed to top 7 times earth's gravity on reentry with a lofted reentry, while a pure ballistic reentry could top 20 Gs. This is important to the launch vehicle's performance because were an abort to occur late in the flight it could mean the difference between life and death. The flight profile of both the Falcon 9 (when mated with the Dragon capsule), and the Ares I is designed to impart horizontal velocity early in the flight. Its much more efficient to rise above the atmosphere vertically, then pitch down and gain orbital velocity where there's less friction. However, if something goes wrong with the launch vehicle right around that pitch down maneuver the astonauts aren't going to be able to utilize the capsule's lifting capabilities to slow their descent. Instead they're going to drop like a rock for 40 some odd miles before they hit meaningful atmosphere and then they're going to encounter a sustained 15+Gs. Thus both the Ares I and Falcon 9 are designed to give their occupants a fighting chance at survival by letting the capsule act as it would on a normal reentry. The Atlas and Delta (the Titan has been eliminated, and the Centaur is an upper stage used on both the Atlas and Delta) are currently incapable of putting an Orion capsule into orbit with the flight profile that allows crew abort survival. United Launch Alliance is now claiming that an uprated RS-68 in the Delta IV, or the currently shelved Atlas 5H would allow them to get an Orion into orbit along the prefered flight profile. They also say that with a number of launches and an Advanced Centaur upper stage, they could do the moon return program at much lower cost than the Constellation program. A lot of their material shows a multi-core heavy launcher, but their documentation indicates that this would be in the 75 metric ton to LEO range (roughly the same as the Jupiter 130, the smaller of the two), and would be in the "After 2025" timeframe, well after even the Ares V could be flying. It seems that the Augustine Committee is leaning heavily toward that option as "Commercial space launch". Something unsurprising when one considers that Mr. Augustine is a former LockMart executive, and LockMart is a partner in ULA with Boeing, and that ULA maintains a near monopoly over every launch that is not done by NASA, SpaceX, or Orbital Sciences Corp. At the moment SpaceX has yet to fly a launch vehicle from the continental US, OSC has done a few air-dropped Pegasus and former ICBM launches, and if ULA has their way NASA will get out of the space launch business as well. This isn't so much 'commercial space flight' as it is a privatized Air Force and NASA spaceflight program through a sole-source contractor. I have no doubt that if ULA suceeds in getting the Constellation program converted to their launchers then they'll start going after the COTS-D contracts SpaceX and OSC are currently operating under to secure their monopoly. It is for this reason that I feel strongly NASA needs to retain both a heavy lift component and a crew launch capability. A lot of the rumblings now are about ditching the Ares I, turning crew launch capabilities over to commercial contractors, and pushing forward a solely heavy lift capability with a modified Ares V or Sidemount booster. However, the Ares V's development is far from assured, and the Sidemount involves a lot of development despite its apparent commonality with the current shuttle stack. The Jupiters may require the redesign of the external tank to accomodate a payload above the nose, but the Sidemount requires a redesign for the greater off-center load, and the Ares V scraps the 8.4 meter external tank-based design for a 10 meter design. With any luck if we go with the Direct Jupiters we'll see cargo launches by 2012, and crewed launches by 2014. Even without a Shuttle extension to 2012 or 2013 a two year downtime in the workforce is far more manageable than the 7 year projected downtime for the Ares I. |
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