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NASA Space Exploration Initiative or The Engine Dilemma

Published by Sigurd De Keyser on Tue Jan 17, 2006 4:45 pm
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By Klaus Schmidt and reviewed by Stephen Deisher, The Space Fellowship; NASA’s new initiative (SEI) has the current final goal (some day they want to go to mars with the, basically, same hardware) to set foot on the moon by 2020 and to maintain a steady exploration from then on onwards. On the first look, their plan doesn’t seem overly ambitious and risky (if one can talk about anything not being risky in spaceflight). NASA’s administrator Michael Griffin called the whole program “Apollo on Steroids”, referring to NASA’s moon program of the sixties.

When we compare the two programs, a few things are remarkable. The Apollo program took 8 years (1961-1969) while the new initiative (when we take 2018 as envisioned by NASA as their wish landing time) will take 13 years. So it will not have quite the pace of the first moon program. One can say that in the 1960s the United States had a space race with Russia, so they pushed very hard. Ok, the other can answer, that’s right, but that time they knew nothing about spaceflight, about procedures, technologies, and all the necessary stuff. That knowledge was developed through the Mercury, Gemini, and Apollo programs, and is still available today. But it’s ok that NASA won’t push the program like Apollo. It’s better to go a steady way.

As many parts are quite similar to the Apollo program, quite a big change is planned for the new moon program regarding the flight profile. While NASA chose a Lunar-Orbit-Rendezvous (LOR) concept back in the 1960s because of complexity (EOR – Earth-Orbit Rendezvous, launching several carriers to LEO and dock the single parts to the moon craft) or payload capacity (Direct approach, a giant nuclear powered Nova rocket puts the whole craft on a direct path to the moon surface), the new program will combine two of the procedures: Earth-Orbit-Rendezvous and Lunar-Orbit-Rendezvous (EOR-LOR).

It is planned to launch the lunar lander and the earth escape stage on an unmanned launcher and after that launch was successful, to launch the Apollo-like crew capsule CEV (Crew Exploration Vehicle) afterwards. The CEV will dock with the other part of the moon craft and the escape stage will shoot them to the moon. There the crew (All four astronauts out of the CEV this time compared to two of the three that flew to the moon with Apollo) will change into the moon lander and land onto its surface and stay there up to two weeks (later on, they want to extend their stay with additional life support systems up to six months). So four persons for two weeks are quite a dose of steroids compared to the two for one week with Apollo. After their stay they’ll launch just like their predecessors in Apollo to the Lunar Orbit and rendezvous with their CEV, change seats and fly back to the earth, where they will drift down under large parachutes to their landing zone (instead of the splashdown of Apollo, the CEV is planned to land on Edwards Air Force Base in California).

One can say, fine, let’s do it and go to the moon, all we have to do is use our more advanced electronics and materials and put it into the old Apollo vehicle. But it’s not that simple. A major hurdle seems to be the engine part: Apollo used 15 engines comprising of 5 F-1’s, 6 J-2’s (five in the second and one in the third Saturn V stage), 1 Service-Module engine, 1 lunar descent and 1 lunar ascent engine. The new program wants to use nearly the same number of engines, 14 (if we don’t count the SRBs), but instead of the Apollo program they want to use the higher-performance (as well reusable) Space Shuttle Main Engines (SSMEs). Their heavy-lift launcher consists out of two solid-rocket-boosters (SRB) flanking a modified Space Shuttle external tank with 5 SSMEs and on top a second stage with 2 J2-S+ engines (simplified Saturn V engines developed at the end of the Apollo program, a bit uprated for SEI). The lunar lander will have 4 RL-10 engines (the same as on the US Centaur upper stage) on its descent and a single new methane-fed engine for ascent. The same engine will power the CEV as it’s envisioned to produce the methane fuel someday out of the martian atmosphere or the lunar regolith. The CEV is launched on a rocket with a SRB as first stage and a second stage powered by a SSME.

They want to use six SSMEs for every single mission (and throw away the reusable engines). Not only that the price tag for a single SSME with about $60 million (that makes $360 million for every single moon flight only for the SSMEs) is high, but it’s also a logistics problem (say the time to build the engines). In comparison, the new RS-68 engine (even stronger than the SSME) costs about $12 million. Rocketdyne has promised to reduce the costs for a SSME from $60 to $40 million dollar in a non-reusable version but how they want to achieve that is not clear.

Currently the time to manufacture a SSME is about two and a half years. When they want to fly two missions every year they’ll need 12 SSMEs for that task alone (ISS operation and supply not even considered). On the one hand, it seems as a chance to “mass”-produce them and lower therefore the costs but on the other hand it will be necessary to hire additional personal to maintain such a high manufacture rate and to guarantee safety and reliability and that will render the cost savings obsolete.

NASA’s talking proudly about the possibility/capability to reuse their command capsule up to ten times, but compared to the launch mass of many hundred tons are the 9 tons of the command capsule not very much not only compared to mass. Expensive (for a different kind of mission type designed) SSMEs are thrown away by the half-dozens each launch. There they should have taken a cheaper engine design.

NASA’s administrator Griffin talked about “pay when you go” when presenting the program to the public, referring that the program is designed (unlike the shuttle which requires constant maintenance) as a non-reusable program. Griffin advertised the program with the possibility to launch more missions a year if funding is available or less of funding is needed elsewhere. But he shouldn’t forget that he can’t fire the personnel each time when NASA has insufficient funding the launch to the moon and hire a new staff when money is available. So, by using that many fundamentally different engines and components of the shuttle program, NASA will still need quite a large staff to keep that program running.

But in the end, it’s better to do something than to do nothing and in the past NASA, most time, chose the last option. Many studies, concepts and programs died just after starting them, so it is important that this program, even if it’s not the best imaginable, will pushed through its single stages without political interference. The first touchstone will be 2009 when a new US president will be elected. So NASA has three years to put the program on a solid fundament.

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