NASA picks Aerojet Rocketdyne engine for SLS upper stage

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Government in slow motion: Only six years after program start, NASA has finally chosen Aerojet Rocketdyne’s legacy RL10 rocket engine for the upper stage of the SLS rocket.

The RL10 is an expander cycle liquid hydrogen/liquid oxygen rocket engine typically used on upper stage applications. It was first developed by Pratt & Whitney in the late 1950s and first flown in 1963. It has flown on hundreds of launches, logged approximately 15,000 hot fires, and accumulated more than 2.3 million seconds of hot fire operation time with a demonstrated reliability ratio greater than 0.999 throughout its history. The RL10 – which is used in various forms with Atlas’ Centaur Upper Stage (RL10A-4-2) and Delta IV’s Upper Stage (RL10B-2) – has a history back to the Saturn I’s S-IV Stage.

No other engine exists that can be built in time. Even so, the engine will not be ready for the first SLS launch tentatively scheduled in 2018, but will instead be used on the next two flights. The article also indicates that NASA is planning to delay SLS’s second flight two years to 2023, creating a five year gap which they will use to integrate the RL10 into SLS, while also rebuilding the mobile platform used to move SLS to the launchpad. (For some reason, the reconfiguration installed for the first SLS flight won’t work for later flights.)

The delay to 2023 has not been announced officially, but I have seen too much evidence recently, including statements in this GAO report, that tells me the delay is certain. Furthermore, it seems increasingly likely that the second flight will also be unmanned, and it won’t be until the third flight (as yet unfunded by Coingress) that humans will finally fly on SLS.

The cost? I am doing an analysis of this subject right now for a policy paper I am writing for a Washington think tank, and my preliminary estimate exceeds $41 billion for NASA to fly just one manned flight of SLS. That’s a bit more expensive than the $10 billion NASA is paying SpaceX, Orbital ATK, and Boeing to launch more than a dozen cargo freighters and as many as a dozen manned flights to ISS.

For those elected officials out there who have trouble with math, let’s compare again:

  • SLS: $41 billion for one flight, 15 years development to first flight.
  • Commercial space: $10 billion for two dozen flights, 5 years development to first flight.

Which costs less and gives more bang for the buck? Can you figure that out, Congressmen and Senators? If you need help I can provide you a few more fingers so you can count above ten.


  • Cotour

    Your analysis illustrates perfectly my point in the previous TSA post and the nature of the government think that drives such abuses of power and the peoples money. Government can not acquire enough of the peoples money, they can not help themselves and it can only result in eventually acquiring more and more of it until there is nothing left and chaos must ensue. Elections really do have consequences.

    From previous post:


    My comment on “trickle down” economics was more a general comment on the nature the flow of cash, someone is paid and they spend their money in my establishment it “trickles down” to me and not a technical analysis of the economic theory. Call that what you will.

    In addition it was a comment on the “free” nature of the money that government spends and governments attitude about what it is and where it comes from and its effects. The problem being that it is ultimately a death spiral thought process, government can not create the wealth that they are in the process of appropriating and removing from the public’s bank accounts. The more they spend the more legal obligation that they create for the public to disgourg their own money through more and more taxation in the name of “progress”.

  • wodun

    I am not really fond of the way cost is determined for government launches by adding up all the costs since the program began and then dividing by the number of launches. It is a useful metric but it also isn’t the true cost of any given launch.

    It leads down the road to the sunk cost fallacy which can play out two ways. One, people might say, “We have invested so much, we have to continue.” This is bad because future costs are what is important going forward. Two, people could make the reverse claim “We have wasted so much, we have to stop.” Again looking at only the past costs and not the future costs, which are the important part.

    You can’t go back in time. That money is gone.

    In this case, we can point to how much has been spent with little to nothing to show for it and that future costs will be ridiculously high both in terms of how much more will need to be spent to complete the SLS system and in operations and maintenance costs for a low production and low flight rate.

    Right now with SLS, the costs are not sunk exactly but ongoing.

    To me, the most convincing case against SLS is one of alternatives for the same amount of future or current money. Sure, you can look backward at how much money was wasted on SLS and then divide that by Falcon 9 launches and multiply that number by payload to get a rough mass to LEO. However, doing this for money being spent now and in the near future is much more compelling reason to change course.

    This is especially true because we have to wait for SLS to become operational while alternatives exist right now. Its a very real comparison of opportunity cost.

    Something I found while playing with the numbers is that doing the alternative cost analysis for just Orion or just SLS was damning enough but at the end you get to say and we could still spend $N billion a year, from whichever one that wasn’t part of the analysis, on payloads.

  • Joe

    Why am I reminded of the windmill (tower?) in Animal Farm every time I read of the SLS project?

  • Christopher Cecil

    Just a note. The RL 10 off the shelf cost is 38 million. A lot of hand fabrication and loads of silver braze. Maybe a RP1 lox engine would cost less ?

  • Edward

    Do you mean that we spent tens of billions of dollars and lost half a century only to end up with what we had before: the Saturn V (but not as good)?

  • Joe

    Edward, yes, right on point, spend money like its going out of style and get nothing in return. The Soviets were into big grand five year plans, and this sounds just like what the Soviets were doing, too what end!

  • Dick Eagleson

    First, a minor quibble. It isn’t the RL-10 that needs to be gotten ready for SLS so much as it is both the Interim Cryogenic Upper Stage (basically a variant of the single-engine Centaur) and Exploration Upper Stage (a completely new stage that is to use four RL-10’s). The former will fly exactly once according to current plans, so the money spent on its custom tankage and fitments will be, in essence, a pre-planned waste of money. The EUS, which could reasonably have been well along in design and construction by now, is, instead, barely getting underway and, as you note, its tardy start guarantees large and unknowable amounts of rightward slippage in SLS’s schedule. Given that the EUS, being a new stage, has never flown before on a mission with humans aboard, NASA has magnanimously decided to follow its own rules and do one entire unmanned test flight before putting people atop the thing. The required modifications to the SLS launch platform seem related to the fact that EUS will be both wider and taller than the glorified Centaur to be employed for the singular SLS first unmanned test mission.

  • From what you write, it appears that the planning and construction of SLS is actually far worse than I had imagined.

  • D K Rögnvald Williams

    All this makes what NASA accomplished in the sixties incredibly impressive. Of course, there is no Von Braun guiding the U.S. space program today.

  • Edward

    “Of course, there is no Von Braun guiding the U.S. space program today.”

    Yes there is! Congress is directing the design of the SLS.

    Oh, wait. I see what you mean.

    Suddenly, it make so much sense why there are all these problems. Politicians are not exactly rocket scientists (but they play them in the Capitol). (upper left corner)

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