SpaceX rockets and launches

Discussion in 'science, nature and environment' started by rover07, Mar 10, 2013.

  1. rover07

    rover07 has a shining car.



    Space X's Grasshopper reusable rocket gets its 3rd test flight. :D
     
    stuff_it, Nylock, teqniq and 3 others like this.
  2. HAL9000

    HAL9000 Lasting Damage

    is Jonny Cash strapped to the rocket? ;)
     
    rover07 and teqniq like this.
  3. ferrelhadley

    ferrelhadley These violent delights have violent ends.

    Very similar to the delta clipper.

    The aim is to have a reusable rocket, that the extra fuel would be more than covered for by the cost of not having to build a new rocket every time. Potentially game changing approach.
     
  4. Crispy

    Crispy The following psytrance is baṉned: All

    3x larger than the DC-X though.

    Also, they're going to try "landing" the 1st stage of regular Falcon flights at sea from now on, as practice. The rocket will fall into the sea and sink, but hopefully it will have come to a controlled halt first. That should be fun to watch!
     
  5. MikeMcc

    MikeMcc Well-Known Member

    The next flight should be using the Falcon 9 v1.1, using the Merlin 1D engines which deliver more thrust. So they are going to use that as a test bed for some of the return to ground functionality. There is also a new version of grasshopper that they hope to launch to 300k ft (about 50 miles).

    http://nextbigfuture.com/2013/03/spacex-may-try-to-land-recover-first.html
     
    stuff_it likes this.
  6. Crispy

    Crispy The following psytrance is baṉned: All

    New footage of the grasshopper's latest hop. This time to 250m, and filmed from a remote controlled hexacopter. Watch it lean into the wind! They're landing with the thrust:weight ratio greater than 1 now, which takes precision timing. Seriously impressive. I can't wait to see one of these things come hurtling out of the sky after liftoff and come to a dead stop.

     
  7. HAL9000

    HAL9000 Lasting Damage

    When you say "landing with the thrust:weight ratio greater than 1", I assume this is happens when the fuel is almost exhausted so simulating a likely landing scenario?
     
  8. Crispy

    Crispy The following psytrance is baṉned: All

    That's right. The "easy" way to land a VTVL rocket is to approach zero altitude asymptotically. You slow down gradually until you're "hovering" at zero altitude, with thrust exactly matching the mass of the vehicle. Then you turn the engine off and fall the last few centimeters onto your landing legs.

    landingeasy.png

    This requires deep throttling of the engine, as the mass of an empty rocket stage tiny compared to a full one. Throttling an engine tends to decrease its efficiency - you get less thrust per kg of fuel burned.

    A more fuel efficient trajectory is to use the engine at full power, which slows you down much more quickly. The trick is to time it just right so that altitude and velocity reach zero at exactly the same time. If you keep the engine on like this, the falling rocket will slow, stop on the floor, then rise again. So you turn the engine off at the bottom of the curve.

    landingjustright.png

    Of course what you don't want to happen is start slowing down too late.

    landingtoolow.png

    Or too soon.

    landingtoohigh.png

    Because you don't want to hit the ground, or waste fuel oscillating up and down.
     
    Enviro, electroplated and Fez909 like this.
  9. Crispy

    Crispy The following psytrance is baṉned: All

    In fact, someone over on this thread has done the calcs and found the most fuel efficient landing trajectory for a Falcon 9.1 first stage. It requires hurtling directly towards the landing pad at terminal velocity (150m/s, or 335mph), waiting until the altitude is 110m, 0.7 seconds before impact, before igniting two of the 9 engines at full throttle, which decelerates the vehicle at 10Gs and stops it just in time. Takes just 750kg of fuel :cool:. A wee bit risky, mind.

    The real thing will bleed off some speed with a burn whilst on a falling trajectory that impacts the ocean. Only when the engine is confirmed to be running ok will it steer the trajectory onto land, after which the landing procedure will look a lot like the 2nd half of the video we just saw.
     
  10. tombowler

    tombowler still missing the point

    this may be a stupid question but how do they steer it/ keep it on course?
     
  11. Crispy

    Crispy The following psytrance is baṉned: All

    The main engine can be pointed left-right/up-down by a few degrees, which imparts a bit of sideways thrust. If you imagine balancing a broomstick on the palm of your hand, this is the side-to-side motion you need to do to keep it upright. In addition, the grasshopper has cold gas thrusters (which literally puff little bursts of compressed air) to control roll, along the long axis.
     
  12. tombowler

    tombowler still missing the point

    ah I did not spot those side cold gas thrusters that makes sense now. thank you
     
  13. Crispy

    Crispy The following psytrance is baṉned: All

    Very impressive new video. This has been done by smaller rockets, but nothing this big has shown such precision in moving sideways in flight.

     
    teqniq and ferrelhadley like this.
  14. Crispy

    Crispy The following psytrance is baṉned: All

    It should be noted that the whole thing was done in a 20 knot crosswind, too. That's windy enough for the space shuttle to have cancelled a landing and stayed in orbit.
     
  15. beesonthewhatnow

    beesonthewhatnow going deaf for a living

    That would be fucking amazing to watch :D
     
  16. Crispy

    Crispy The following psytrance is baṉned: All

    You'll get the chance to see it on the next Falcon 9 launch. They'll be testing the return and landing procedure, except they'll be aiming for the ocean, not the land.

    The actual return-to-pad trajectory will not be far off tbf. The rocket will come screaming in at terminal velocity on course to impact in the ocean near the pad, or into a specailly constructed "crash pit". Then it will turn the engine on and slow down rapidly (thrust:weight ratio of over 3), making a sideways move just like the one in the video in order to hit the pad instead.
     
  17. beesonthewhatnow

    beesonthewhatnow going deaf for a living

  18. Crispy

    Crispy The following psytrance is baṉned: All

    Also, expect to see much higher hops, including engine shutdown, coast, relight flights using Grasshopper 2 at the Spaceport America site in New Mexico. 300,000ft maximum altitude.
     
  19. Bob_the_lost

    Bob_the_lost Elsewhere

    It's not that hard
    [​IMG]
     
  20. Tankus

    Tankus living someone else's dream.

    ?? ...the McDonnell delta clipper rocket was doing all this and a hell of a lot more ,almost two decades ago ....?
     
  21. Crispy

    Crispy The following psytrance is baṉned: All

    Yes, but it was 1/3rd the size and designed specifically for that sort of manoeuvre. I read a lovely metaphor on the NSF forum:

     
  22. Tankus

    Tankus living someone else's dream.

    Its not a toy though , and they have had two decades in which to scale it up
    [​IMG]
     
  23. Crispy

    Crispy The following psytrance is baṉned: All

    No doubt. If it hadn't been for X-33 eating all of NASA's SSTO R&D money, it could have gone somewhere.
    But a VTOL SSTO is damned hard anyway. Your mass fraction is going to be terrible, if not zero, unless you use exotic engine technology like aerospike or mixed mode (air-breathing rocket).
    I like the approach that SpaceX is taking - make the first stage reusable and you've already saved yourself the majority of the cost of the rocket. It's 90% of the engines and 75% of the tanking. It's much much easier than recovering the whole vehicle, and lets you test technologies while flying commercial missions. Win-win, IMO.
     
  24. MikeMcc

    MikeMcc Well-Known Member

    Helps when it doesn't crash and burn up...
     
  25. Crispy

    Crispy The following psytrance is baṉned: All

    DC-X didn't really crash, it just fell over. The project was being run into the ground anyway.
    Besides, test vehicles are kind of *supposed* to crash. That way you find out what they can't do.
     
  26. MikeMcc

    MikeMcc Well-Known Member

    Yeah, I did have to change the post from explode to burn up too...
     
  27. rover07

    rover07 has a shining car.

    First launch of the new Falcon 9, today at 5pm.

    http://new.livestream.com/spacex/F9-6

     
  28. Crispy

    Crispy The following psytrance is baṉned: All

    I will be amazed if they manage to bring the 1st stage down in a controlled manner. It will look incredible if they do :)
     
  29. rover07

    rover07 has a shining car.

    Yep looking forward to seeing this! I hope they show it live! :D

    How long after launch do you think it will be? I imagine it will come straight down after separation, 10 mins maybe?
     
  30. rover07

    rover07 has a shining car.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice