Half a croissant, on a plate, with a sign in front of it saying '50c'
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rocket see-saw

giving that initial boost
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a vast quantity of rocket fuel is used in those first few seconds of flight when mass is heaviest, and they have to overcome all that inertia.

I propose a giant see saw instead of a normal static launch pad. On one side would be a giant set of counter weights and on the other the rocket. some sort of mechanism would lock the counter weight in the armed position

During rocket launch the counter weight could be timed with the rocket ignition, depending on the stroke length and weight, it could provide that initial 10-50 M/S of force and reduce fuel consumption and rocket size significantly.

Much easier than building a miles long rail gun.

metarinka, Jul 23 2011

Jet ponies http://www.youtube....watch?v=JA3hArg8rr0
Red hot steel and flames. Does it get any better than this? [Klaatu, Jul 24 2011]

[link]






       Interesting.   

       But why would this be better than, say, building a tall (really tall) launch tower and boosting the rocket up it using an external power source?
MaxwellBuchanan, Jul 23 2011
  

       //miles long rail gun// why not build a vertical rail gun ? Run the rocket up that.
FlyingToaster, Jul 23 2011
  

       see saw is cheap, rail gun is not as developed of technology.   

       I always wonder why more effort hasn't been put into rail gun launch technology
metarinka, Jul 23 2011
  

       //see saw is cheap//   

       But also not very effective - a 'mile long' rail-gun can accelerate the rocket over a distance of a mile; a workable see-saw will act over a much shorter distance. Assuming that, in each case, you accelerate the rocket as hard as its payload can survive, you're going to get a tiny fraction of the velocity out of a see-saw.   

       (Suppose your see-saw has a travel 500m, which would be a very, very big structure indeed; and suppose it accelerates the rocket at 10G. It's going to push the rocket for 3 seconds, giving it a speed of 300m/s.)
MaxwellBuchanan, Jul 23 2011
  

       I was rather hoping for an item of extreme playground equipment, loaded with dangerous substances like hydrazine, but I like it anyway [+]
AbsintheWithoutLeave, Jul 24 2011
  

       //why not build a vertical rail gun ?//   

       If you send a rocket or something straight upwards, it'll come straight back down again. Rockets usually need to give their payload a hefty sideways push as well, to get it into a useful orbit.   

       I suppose this might work as an alternative to an ICBM, though.
Wrongfellow, Jul 24 2011
  

       // those first few seconds of flight when mass is heaviest //   

       Do you mean, "when the rocket assembly has the greatest mass" ?   

       // hoping for an item of extreme playground equipment //   

       Funny you should say that ...
8th of 7, Jul 24 2011
  

       // hoping for an item of extreme playground equipment //   

       Like the link?
Klaatu, Jul 24 2011
  

       /// those first few seconds of flight when mass is heaviest //   

       Do you mean, "when the rocket assembly has the greatest mass" ? //   

       well technically the further you get away from the surface the less your mass weighs. But you're right I did mean the less mass you have, I remember some figure about how much it rocket fuel was used in the first few hundred feet, it was significant.
metarinka, Sep 06 2011
  
      
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