luke strawwalker
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Hmmm... learn something new every day.
I guess they figure Blue Origin will be cheaper than PWR... and they're probably right. OTOH, maybe PWR has been looking long and hard at building copies of the RD-180 and found some "show stopper" that will make it impractical for them to do so. Given the complicated nature of a closed-cycle engine like RD-180, and the unique metallurgy that allows the LOX-rich combustion, and the costs associated with not just cloning the design, but building the TOOLING necessary to make the components and the PROCESSES necessary to put it all together into a working, certifiable engine, well, it may have proved a bridge too far, if not technologically, then probably almost certainly from a cost standpoint.
A reapportionment of the propellant tanks of Atlas V wouldn't be THAT difficult. Simply do a tank stretch on the LNG tank as necessary to hold the proper amount of propellant for the size of the LOX tank. Tank stretches on rockets are pretty straightforward and have been done for decades. However, there's a MUCH better alternative...
Retire the Atlas V, and go to the Atlas V Phase 2 proposal. In short, Atlas V Phase 2 was proposed as a potential successor to increase capability for the VSE, back when O'keefe and Steidle were in charge of NASA and planned a "spiral development" program to fulfill the requirements of the VSE and replace the shuttle when it was retired. Basically, Atlas V Phase 2 would dump the 3.8 meter (IIRC from memory) core of the Atlas V, and build a new core on the larger 5.5 meter (IIRC from memory) Delta IV tooling, reapportioned for the propellant volumes of LOX/RP-1, and powered by a PAIR of RD-180's. This would make a vehicle roughly analogous to the Saturn "C-3" vehicle (which would have been powered by a pair of F-1 engines) or the "Jarvis" launch vehicle proposal of the immediate post-Challenger time period... (ET diameter tank holding LOX/RP-1 feeding a pair of F-1's on the first stage, lofting an ET diameter second stage powered by a single J-2S). Since you're switching to LOX/LNG, design the core to be powered by FOUR of these Blue Origin engines, with the Delta-IV size tooling. Basically, the tooling and lines producing EELV's have been underutilized all along, because the demand for the EELV's didn't materialize... The EELV's were designed with a production capability of about 45 cores per year IIRC, and of course NEITHER of the two vehicles fly anything like that often. Then there's the additional costs of producing TWO vehicles, BOTH of which are underutilized, and all that extra capacity costs money that has gone to waste. The low flight rates of BOTH vehicles also increases costs per launch because the support infrastructure is spread over fewer actual vehicles, increasing the cost per vehicle to support that overhead and infrastructure. Having two different vehicles also doubles the costs, since now you have TWO sets of overhead and infrastructure support programs to pay for instead of one. The only thing all that inefficiency buys you is redundancy, which isn't a bad thing... but is it worth the cost??
It made sense to do it that way when the EELV's were approved and designed back in the 90's, but that was then, this is now. Now we have alternative "backup" vehicles in case some flaw or launch vehicle failure is exposed that grounds the fleet for awhile until it's fixed, which wasn't really the case in the early 90's (back when for most national security launches, your only choice was shuttle or Titan IV in most cases). Now we have Falcon 9, which the AF is loathe to approve and is foot-dragging and being as obstructionist as possible to approving Falcon 9 for military launches, due to the fact that they really don't want the competition with their own vehicles, the EELV's.
The "Atlas V Phase 2.2" (since this would be different than the original Atlas V Phase 2, since it would use LO2/CNG for propellants instead of LO2/RP-1) would be built on the same line and tooling as the Delta IV, allowing for increased utilization of the overhead and infrastructure to build Delta IV, lowering costs. It would allow the retirement of the smaller Atlas V tooling and line, reducing the programmatic costs of maintaining the capability to produce both the smaller and larger core diameters. Basically you'd still have redundancy, since the propulsion systems of the Delta IV, powered by liquid hydrogen burning RS-68's, and the LNG burning Blue Origin engines, would be very different... the only thing the two vehicles would really share is tank diameters and tooling to produced the tanks (their lengths would be different due to the density/volume requirements of the different propellants, and the different mixture ratios of LO2/LH2 burning in an RS-68, and LO2/CNG burning in the Blue Origin engines.
Since they specifically mentioned something about replacing the engines on Delta IV at some point, it really sounds like this is their intention eventually... it makes a lot of sense. Delta IV tankage with Atlas V (Blue Origin) engines...
It would allow you to continue to use the Delta IV Heavy infrastructure (including the common core "heavy" configuration, with some modifications). Modifications to the pad and infrastructure to accomodate LNG either alongside or in place of LH2 shouldn't be too difficult. LNG is cryogenic, but not as deep a cryogen as LH2 is.
LNG/LOX isn't going to have the ISP of LH2/LOX, BUT, RS-68 isn't maximizing LH2 ISP anyway, and basically LH2 is a pretty lousy first stage propellant anyway. LNG has a lot of advantages, more similar to kerosene than LH2, but with a little better ISP than kerosene, even if it is a little harder to store and handle than kerosene (but still easier than liquid hydrogen). It's a pretty good tradeoff when you think about it.
Makes a lot of sense when you look at it...
Later! OL JR
