An engineer’s take on Elon Musk’s proposal to make Falcon 9 reusable


Please consider donating to Behind the Black, by giving either a one-time contribution or a regular subscription, as outlined in the tip jar to the right or below. Your support will allow me to continue covering science and culture as I have for the past twenty years, independent and free from any outside influence.

Clark Lindsey asked an engineer experienced in building reusable spaceships for his take on Elon Musk’s proposal to make Falcon 9 reusable. The answer is fascinating.

Share

One comment

  • Kelly Starks

    Yeah I was about it to.

    SpaceX has kind of been all over the map with theFalcon-9. They started with the idea they were going to reuse Falcon-9s – but a ICBM style boosters about the worst place to start if you want a RLV. Originally they were going to parachute the stages into the ocean and fish them out for reuse –guess they figured that would likely beat the crap out of them – then corrode them. [The SRBs get trashed by water impact – you pretty much just reuse the steel cylinders.]

    As for this Idea. Its kinda of like the Kistler, but it parachuted to the ground and landed on inflatable bags, last I remember?

    As to things that worry me about the new Falcon design?

    – Generally folks looking at designs like this have said the power to boost the first stage to a stop, and then boost back to the pad, and rocket VTOL land – eat up a lot of fuel. That could really cut you’re lift capacity. One way to get around the issue for the first stage is have it only boost straight up, stage directly over the base, and land straight down (like in “The Rocket Company” http://www.amazon.com/Rocket-Company-Library-Flight/dp/1563476967/ref=sr_1_1?ie=UTF8&qid=1317567871&sr=8-1 good book by the way) – but then the second stage needs to do all the horizontal velocity

    – 2nd stage has similar issues -plus will you come down in the right distence? I mean by that a full orbit – AND you need to boost the empty stage sideways to compensate for the earths rotation under the trajectory (unless you stick to one exact traj that lines up with where the landing site will be.) so its also power consuming.

    – 3rd, reentering a cylindar??!! Balancing it on a nose shield and keeping the stages long thin cylindar? Also the weight of the stage and fuel on that small shield could get pretty heavy per square foot of shield surface. [A flat side would let you skip off the atmosphere and steer.] This is why capsules tend to be short and wide – not long and thin; and ICBM warheads and DC-X designs, aerodynamic cones..

    – 4th – a nit – how do you get the fuel & LOx to always “fall” toward the intakes in these manuvers.

    I haven’t run the numbers for this stuff (hell I just relocated to a new place for a new contract), but off the top of my head these are some of my concerns. Again it looks like a amateurish and complicated kluge, to try to make a ICBM booster (designed for high performance and single use) be a RLV. If he just repackaged the engines and system in a non-ICBM config (Biamese, starclipper, DC-X, etc) he’ld save himself a ton of work and cost!

    Kelly

Leave a Reply

Your email address will not be published. Required fields are marked *