This week NASA announced its Next Big Thing: the “Space Launch System,” a heavy-lift vehicle that will provide the basis for a new generation of crewed deep-space missions, and renew U.S. launch capability in the post-Shuttle era.
Cool. I’m excited. In the space program, it’s okay to equate New with Good. Anything with the potential to expand our knowledge of and presence in the solar system (and maybe even reduce our dependence on our home planet) is worthwhile. And then there’s the ooh-aah factor of the numbers: Three to five times the payload capacity of Space Shuttle! More powerful than the venerable Saturn V! Our biggest rocket ever!
But I’m extremely skeptical about this announcement, and about NASA’s plans for the future—so much so that I have the eerie sense that with this new program NASA has signed its own death warrant.
NASA spent five years fiddling around with the Constellation program before it was cancelled, at untold cost for that abortive development. SLS will require another five years, minimum, before the first test launch will fly—and its first crewed mission isn’t expected to occur until 2025.
Why so long? The answer, of course, is money. We live in an era where the U.S. defense budget is over half a trillion dollars annually, while the education budget is less than one-seventh of that. Congress has flatlined the NASA budget for the foreseeable future. Given those realities, one has to wonder whether NASA couldn’t find a more cost-effective way to spark the public interest, rather than the piecemeal construction of a massive new launch system for the next two decades or more.
Meanwhile, from a hardware standpoint, the SLS plan is far from perfect. NASA has chosen the Rocketdyne RS-25D engine for the main stage, an engine better known as the SSME (Space Shuttle Main Engine). The RS-25 is widely reputed to be the most complicated engine ever built. NASA chose this over the newer RS-68—an engine that is the result of lessons learned from real-world experience with SSME, an engine that has 80% fewer parts, costs less to build, uses the same propellants, and has a reasonable thrust-to-weight ratio—because of the necessity of modifying RS-68 to make it “human-rated.”
The idea is this: NASA has a stockpile of tested RS-25D engines of known quality and reliability—most (if not all) have already been used for Shuttle flights. The cost to take these engines out of mothballs and bolt them to a new airframe is (relatively) minuscule. This defers the cost of main engine development and production until later in the project, which (in the short term) would seem to NASA to be fiscally prudent. Then, the RS-25 would be modified and simplified for expendable use, and production would resume. As the production line comes up to speed, and SLS launches come more frequently, the unit cost of new engines would decrease.
Seems to me I’ve heard this argument before—with Space Shuttle. The high cost of early launches was expected, as the spaceplane reached operational status and made flights with clockwork regularity, to drop precipitously to a downright economical level. Yet Shuttle’s “cheap access to space” never came to be. Hypothetical economies of scale don’t seem to come to fruition very often in the spaceflight game.
I suspect that simplifying the RS-25 to make an expendable version, the RS-25E, requires no less of a development and testing cycle than would be entailed in modifying the existing RS-68 for crewed launches. At the same time, RS-68 already has an existing production line and expectation of continuing use, since it is the main engine of the Delta IV rocket. So why start up a completely separate production line, and employ all those rocket engine builders, for a system that, as currently planned, will need at most five engines per year?
The biggest problem comes down to this: the old adage “time is money.” The longer it takes to get SLS flying, the longer the gap between flights, the more expensive the total program becomes. How many people will be employed, day after day, to make this system happen? What will the ongoing cost be, in salaries and benefits, when it only flies once per year? More to the point: Is this a space program, or a jobs program?
We have the hardware. Assuming the short-term frugality (and long-term myopia) of using RS-25 engines, and with the flight-proven hardware of the Shuttle’s ET as tankage, why must it take six years to get one off the ground? Wernher von Braun and his gang could have whipped together a flight-ready model in much less time—two years perhaps, and four years tops. Just look at what they were able to do with the Saturn I/IB.
If this announcement had come in 1972, in lieu of the Space Shuttle, I’d be excited. Back then NASA might have had the budget and the public impetus—and the gumption—to make it happen, and something exciting probably would have come from it. We might even have walked on Mars by now. But to make this announcement now, with NASA an agency both so bureaucratic and risk-averse as to be vapour-locked, with Congress only allotting it a shoestring budget, and with no clear notion of where SLS might go (and who will pay for it to get there), it seems like too little, too late.