using a giant arm to launch your ships!

[jamieadd]

Would it be possible to make a huge arm that flings your spacecraft into space. It would be so much easier to launch large ships. I was thinking, you have the arm on the runway, that reaches over to the launch tower and grabs to craft. The main problem I have is trying to stop it falling over. I don\'t have time to make one that could get things into space. If any of you can, I would love to see it.

[Khrissetti]

I don\'t see the point, unless it could provide enough of a shove to get you into the lower atmosphere you\'d need to use the rockets soon after taking off, anyway.

[jamieadd]

I was thinking you use a huge arm, 70 km long, and just lift your craft into space, like a huge hand coming down from the sky.

[Plaatinum Aerospace]

Why not just make a slingshot? *calls jeb*

[VincentMcConnell]

No. It\'s impossible. This discussion came up about slingshots once on Yahoo! Answers.

I can\'t find it now. But someone left an awesome answer about the force being so great that it would turn steel to butter.

[Plaatinum Aerospace]

You are right.....

about the slingshot and the awesomeness of turning steel to butter!

[madspy]

MY GOD, I want to turn steel into butter!

THINK.

OF.

THE.

PROFIT.

I could tackle the kerbinwide market of BUTTER. 8)

[Richy teh space man]

A space gun was something the Americans worked on in the 60s, kind of similar idea

http://en.wikipedia.org/wiki/Project_HARP

Main problem is the G forces at the start..

[shhhilent1]

I love harp.

I use it in orbiter 2010.

[Bluejayek]

If you find one of the old drag force threads, i did a calculation of what it would take to clear atmosphere at orbital velocity with a slingshot/cannon. I believe the starting velocity was some hundreds of thousands of meters per second. 700,000 m/s seems familiar.

Now, if we consider doing that with a slingsht, say over a kilometer we get a gforce of 24,999,999g, which is clearly absurd.

Put another way, it is accelerations to 700,000m/s over 2 thousandths of a second. That is 2.45E14J of kinetic energy for a 1 ton spacecraft, for a power requirement of 12.25E17 watts, or 122500TW. The current worlds power production is around 1TW, so it would take over a day to store up the energy required, even if you could somehow store it.

[Ratheld]

If you find one of the old drag force threads, i did a calculation of what it would take to clear atmosphere at orbital velocity with a slingshot/cannon. I believe the starting velocity was some hundreds of thousands of meters per second. 700,000 m/s seems familiar.

Now, if we consider doing that with a slingsht, say over a kilometer we get a gforce of 24,999,999g, which is clearly absurd.

Put another way, it is accelerations to 700,000m/s over 2 thousandths of a second. That is 2.45E14J of kinetic energy for a 1 ton spacecraft, for a power requirement of 12.25E17 watts, or 122500TW. The current worlds power production is around 1TW, so it would take over a day to store up the energy required, even if you could somehow store it.

*yawn*

MOAR BOOSTERS!

In all reality that math is awesome

[khyron42]

I liked one similar concept to the cannon I\'d read about in a sci-fi book.

You lay a pipeline, big enough around for your craft to fit inside. The pipeline climbs gentlly in a straight line towards the east, up the side of a tall mountain near the equator - the sci-fi book used Chimborazo, I think. There\'s a track inside the pipeline for a while, and after that it\'s perfectly straight (computer controlled to keep it that way, especially when it\'s active.)

Your craft is a payload and small second stage built around a very high power jet engine. The engine has no outer casing or fuel lines - just what\'s needed to turn a fuel/air mixture into thrust. It\'s also built to be able to handle the shock wave of going through the atmosphere at launch speeds, starting at the altitude where the high end of the pipe is.

You fill each section of the pipeline with the ideal fuel/air mixture and pressure for the exact speed that the engine will be travelling when it passes through that section. Stick the engine+payload in at the low end , seal the pipeline on that end, fill the pipeline, and light that baby up.

The beauty of it is that this way, you never have to accelerate the fuel to orbital speeds, just the payload + engine. The drawback is when it leaves the pipe, it has to be going way higher speed than what\'s actually needed, and transitions to huge air resistance in a split second right as it loses all active thrust. That\'s going to be your max Q for sure, but a highly aerodynamic craft can minimize the strain at 6 km altitude. This is a way to get most of the advantages of the 'gun' style launcher, while still limiting the G forces that your payload has to withstand - you can tune the thrust of the engine and length of the gun to never exceed the G\'s that will happen when it exits the pipe.

Obviously, you wouldn\'t be launching people this way. ;D

[cardgame]

Mass drivers with electromagnets are the way to go.

[Phoenix Aerospace]

Even better, you\'d have a Lostrom Loop. This is a 2000 km long loop (in normal-universe scale), composed of two concentric tubes; an inner, superconducting rotor surrounded by a slightly larger stator. The fairly tight bends at the ends of the loop would be managed by auxiliary curving magnets. The idea is that you\'d tether the upper part of the loop to the ground, spin up the magnetically levitated rotor, and have centripetal forces push the upper part of the loop 80 kilometres up into the air; above the majority of the atmosphere. Payloads, brought up by elevator, would grapple magnetically to the rotor, and use it to accelerate up to orbital velocity. Obviously, the payloads would need some means of circularization, but it would be minuscule compared to conventional launchers. Theortically, the loop would be able to put six million metric tons of payload into orbit per year, at a cost of $3 per kilo. Oh, and I forgot to mention, they can be built with today\'s technology. Effin\' magnets. How do they work?

Pretty Pictures :

(loop diameter not to scale)

...Though I would put this fairly high on the tech tree. Doing this realistically would just be cheating.

Edit: In accordance with OP, something similar would be a rotovator, which is a rotating tether that dips one of its tips, moving retrograde relative to the tether\'s orbit, into the atmosphere to pluck a flying payload out of the air and fling it into orbit. Naturally, as it trades velocity, and due to drag, its orbit will gradually decay. Of course, this can simply be remedied with RCS, or if you\'re more of a futurist, by having the rotovator act as an electrodynamic tether.