I asked Elon if he could discuss it on the record. His response: “Sorry, but SpaceX is not commenting on Grasshopper at this time, except to say that it is part of a reusability strategy that I’ve had in mind for a long time.”

That fits in with everything else I’ve ever heard (and his adamance that he was going to recover the first stage when I asked him after the first flight). But that doesn’t mean that there couldn’t be a lot more to it, of course,

26 thoughts on “Grasshopper”

  1. All from Spacex website:
    The Merlin has 125K lbs of thrust.
    The users guide says the MVac can be throttled 60 to 100%.

    Guesses for the F9 first stage weight vary from 19 to 28 tons.

    Thus the presumed minimum thrust for a normal merlin would be 75K lbs.

    Using these numbers then an empty F9 and single merlin will be seeing
    1.3G acceleration at a minimum.

    You probably want to target “nominal” ops to be in the center of the throttle range to allow adjustment so that would be 100K lbs and close to 2 G deceleration.

    So they must be contemplating a vertical landing with engine thrust greater than 2x the weight. A very sporty proposition indeed.

  2. It looks like they’ve figured out that you can’t get real, economical reusability by plucking stages out of salt water.

  3. How much nozzle deflection are the outer nozzles capable of?

    That is: Is it enough for a fully splayed-out opposing pair to generate less thrust than the center engine alone?

  4. Al,
    No, not even close. In order to have the nozzles splayed enough to actually produce less thrust than one engine, you need something like 60 degrees off of vertical (if I’m doing my mental trig right). Main engine TVC is typically single-digit degrees.


  5. Part of Elon’s strategy seems to be to keep his companies in the news, regardless of the actual performance. He did the same / is still doing with Tesla.
    They are looking to rack up exactly zero flights in 2011, and now its suddenly RLVs ?

  6. Perhaps the decision makers at NASA will recall the time that NASA “blocked” Dennis Tito from visiting the station. We probably have more leverage than they did back in their days of abject poverty, but I suspect the powers at NASA have far less balls.

  7. Trent,

    Its logical capitalist behavior, block competitors by any means possible. The Russians have learned to be very good capitalists.

  8. I don’t think that’s logical behavior. Avoiding competing on the merits of your product seems like a good strategy when your product is crap, but when you have a good product – which the Russians do – using underhanded tactics just invites others to do the same to you.

  9. Logical behavior and competition often have nothing to do with one another. My family had a nice Italian restaurant across the street from a diner that decided to put us out of business. He heavily advertised his bucket-o-spaghetti. We didn’t advertise a dime and he was extremely successful at driving traffic to our restaurant. Funny as hell.

    SpaceX isn’t building their business to support ISS alone. Elon is a lot smarter than that. Losing ISS will slow them down, but not stop them.

    It’s a real good lesson in government contracting if he wasn’t aware before.

  10. We probably have more leverage than they did back in their days of abject poverty

    Nonsense. We had a lot more leverage back when we had independent access to the station, and were providing our own share of cargo/crew rotation to ISS rather than paying the Russians for all of it.

  11. I think the plan for using this capability is probably more to control the 1st stage during it’s decent rather than land it.

    To land it they would have to add mass and complexity for landing gear, whereas if they use active control for reentry and splash down that may be all they need.

    They have already built the Falcon 9 for water recovery, it’s just that none have survived the reentry. I think this addresses that problem, and nothing more.

    That Musk doesn’t want to focus on it is probably because there is no upside for it unless it’s a complete success, and who really cares if they are recovering their 1st stage. It only matters if the mission was a success.

  12. If the idea works, they may be considering some variant of the flyback booster. I wonder if, instead of trying to return to the launch site, they could land on a ship, barge or island along the flight path. That would seem to take a lot less propellant than flying back to Florida.

  13. Larry: I could see them using this idea for the strapons of the heavy lift variant. Those will stage at lower range/velocity than the first stage of the Falcon 9 (because in addition to firing their engines, they will be feeding propellant to the booster’s first stage).

  14. Trent,

    Ken, is right. The Russian’s come from the J.D. Rockefeller school of capitalism, in which no competition is the best competition. As for payback, if you drive your competition into the ground they won’t be around to get back at you 🙂

    I wonder how fast SpaceX could switch out the Dragon suppy craft for a DragonLab. Bumping up the flight schedule of the DragonLab would make a number of biotech firms happy.

  15. If it is for booster recovery then I expect SpaceX to fool with it for a year or so, then realize the penalty of wings and landing gear is more then offset with the ease of reprocessing a booster that simply lands on a runway versus one from an ocean recovery.

    In addition a flyback booster opens up inland sites for launch, giving him both a potential attitude advantage as well being able to launch polar and easterly from the same carefully selected site.

  16. Elon intends to recover his first stage. They’ve decided that they need an incremental way to study the problem that regular F9 launches don’t give them. It also gives them real world data rather than simulation data for VTVL software. While a surprise to us not in the know, it makes sense.

    This is the same thing they did with F1 before F9. It’s a cheaper way to study certain problems.

  17. I’m betting both the “improved splashdown recovery” and the “true VTOL” theories are correct, in time-series order. This technology is useful for both. First they’ll improve their splashdown recoveries, and then flyback (or downrange landing) comes later.

    This will be useful for the Falcon Heavy before the technology allows the F9 to benefit from it, since the boosters release at lower altitudes and velocities than the F9 first stage. If they can improve the recover from 0/3 to 2/3, that’s a significant cost-savings right there, even if they never get the F9 to splashdown safely.

  18. Why are the launch hopefuls wasting time trying to make their inventions re-usable? Shouldn’t they try to get to orbit and back safely first?
    Coke and Pepsi didn’t think about recycling until their sales reached a volume where waste was becoming obvious. A few hundred used boosters scattered on the bottom of the Atlantic east of Florida might be profitable to Waste Management or another private entity, but is a waste of resources for someone trying to develop a brand new industry.

Comments are closed.