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Catapult to Orbit - SpinLaunch


Shpaget
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Couldn't they scale it up to limit g forces by using a maglev vacuum tube (hyperloop style, in a circle),   with several 'exit ramps' climbing on mountainside at various headings (so you can target a few different orbits)

Though, friction will still be insane when the stage leaves the tube (use a MHD to limit air friction maybe one it leaves the tube ?)

For large circular facilities with a magnetic tube, LHC is 26km diameter for example :) much more reasonable than a 50m catapult on lateral G forces...
 

Of course, the initial investment is much higher :p

Edited by sgt_flyer
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On 2/8/2021 at 2:21 PM, DDE said:

They weren't the only ones. At least some Soviets argued for a 406 mm gun/missile launcher on the Sovremennyi destroyers.

406 mm gun and destroyers does not compute, 406 mm  or 16" is the guns used on the Iowa class battleships.
Yes you have low velocity guns as in mortars but they don't make much sense on warships as they are short range. 

Think you could make an 8" gun shooting up and launching both shells and missiles who would fit on an destroyer. 

 

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On 2/12/2021 at 3:07 AM, sgt_flyer said:

For large circular facilities with a magnetic tube, LHC is 26km diameter for example :) much more reasonable than a 50m catapult on lateral G forces...

Space station orbital velocity(for reference): 7.66 km/s

according to this: https://www.omnicalculator.com/physics/centrifugal-force

a 13km radius with a velocity of 7660m/s gives centrifugal acceleration of 4513.5 m/s/s or 460g

If you reduce that to half the velocity of the space station(which means a non-trivial rocket for the other 3830m/s), you can reduce that to a mere 115g of off-axis acceleration.

If you used earth's equator(radius of 6,356km) as the largest possible loop, you can get the off-axis acceleration down to 9.2m/s/s which should be readily handled by just about anything on earth that can lay on it's side(which does not generally include a rocket once it is loaded with fuel).

And you would only need to build an air-tight tunnel 40,000km long. (just don't try to make any sharp turns, such as going up a mountain, as that would splatter your ship right quick).

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  • 9 months later...

 

 

Perhaps they are going about it wrong? Since the more moving parts you have in a closed system the more you increase the chance of systemic failure.

The less the better. Problem is that Spin Launch relies on one big part working perfectly or else.

An alternative:

I think trying the same thing and shape with magnetic coils would be better. The building setup would look the same roughly.... just much larger.... using magnets to accelerate a rocket to the required launch velocity.

Actually may work better since you have less stability issues than with catapult arm version.

Scott the arm will have to deal with instability issues since the arm will weigh much less once it releases the rocket.

With magnet coils lining the inner wall permeter of a giant standing disc launch facility, the stability problem is less of an issue.... because less moving parts are involved. The only moving or switching would be switching the alignment of SOME of the coils toward the exit tube before the last revolution of the rocket before launch.

You trade instability of  one huge moving part for smaller ones that weigh less and massive amounts of waste heat, which can be solved with generous amounts of coolant or putting your facility near a water source.


It would be a massve drain on the electrical grid, but it would change space travel as we know it.

 

Did I get this right?

Expensive yes. Possible? I hope so.

 

As Scott Manley said, power generation and spinning is a solved problem... instability is not.

This is my attempt to solve the instability problem.

What do you know on this?

 

Edited by Spacescifi
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Something that has occurred to me and and haven't seen mentioned before - with the plan being to spin the arm at around 450 rpm, once the projectile separates from the arm, the projectile will retain this 450 rpm (7,5 revs per second) rotation. Just a fraction of a second after launch it will be travelling through almost sea level souposphere sideways, not with the pointy end forwards. 

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32 minutes ago, grawl said:

Can a "spin" launch be detected by the traditional rocket launch alarm systems ?

The tip of the rocket heating after tube exit might be enough... But if not I can see a lot of military interest in this... thing.

This version still uses a rocket engine in the second phase of flight. So for an ICBM at least, this wouldn’t work, and in any case, it is just going to get detected by radar and maybe ESM equipment, which will allow for early warning and interception.

But for short ranges, it should. The only downside is that it is very unwieldy- I don’t think you can plop it down on a TEL-chassis and drive it around.

But, there are short range BMD radars too, so it will still get detected and intercepted anyways.

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Moving the launcher\gun would be a witch too. You would have to painstakingly level it again after every relocation. I don't think anyone would want to switch from traditional artillery to this thing. Maybe as an main gun of a space battleship?

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On 11/26/2021 at 4:56 PM, Shpaget said:

Something that has occurred to me and and haven't seen mentioned before - with the plan being to spin the arm at around 450 rpm, once the projectile separates from the arm, the projectile will retain this 450 rpm (7,5 revs per second) rotation. Just a fraction of a second after launch it will be travelling through almost sea level souposphere sideways, not with the pointy end forwards. 

Yes, the projectile will have an initial rotation when released, but it's aerodynamically stable and the aerodynamic forces are extreme.

It won't get far off-axis before getting corrected.

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40 minutes ago, RCgothic said:

aerodynamic forces are extreme.

That's what I'm worried about.

40 minutes ago, RCgothic said:

It won't get far

I'd finish the sentence here. At 7,5 revs per second it takes only 33 milliseconds to rotate 90° (a good chunk of that rotation is still in vacuum in that chimney thing). It will have already be partially turned sideways before it encounters air. I don't feel confident about survivability of those fins, or anything else inside, for that matter.

I'm trying to figure out what's the force of drag on a cylinder (1 m diameter, 5 m long*),  travelling sideways through a sea level atmosphere at Mach 6, but my googlefu is letting me down. Anybody good at supersonic aerodynamics?

*eyeballing from this pic:

Sunnyvale%2520Lab.jpg

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3 hours ago, Shpaget said:

That's what I'm worried about.

I'd finish the sentence here. At 7,5 revs per second it takes only 33 milliseconds to rotate 90° (a good chunk of that rotation is still in vacuum in that chimney thing). It will have already be partially turned sideways before it encounters air. I don't feel confident about survivability of those fins, or anything else inside, for that matter.

I'm trying to figure out what's the force of drag on a cylinder (1 m diameter, 5 m long*),  travelling sideways through a sea level atmosphere at Mach 6, but my googlefu is letting me down. Anybody good at supersonic aerodynamics?

*eyeballing from this pic:

Sunnyvale%2520Lab.jpg

At Mach 6 in 33ms the projectile will have travelled nearly 70m, which is many body-lengths. It will stabilise.

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2 hours ago, RCgothic said:

At Mach 6 in 33ms the projectile will have travelled nearly 70m, which is many body-lengths. It will stabilise.

But at least 50 of those 70 m are still in vacuum. It won't stabilize if it can't survive the first sideways impact with the air. It will have turned almost 60 degrees away from straight ahead before it encounters air.

eSvPiQ2.png

 

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2 hours ago, Shpaget said:

But at least 50 of those 70 m are still in vacuum. It won't stabilize if it can't survive the first sideways impact with the air. It will have turned almost 60 degrees away from straight ahead before it encounters air.

eSvPiQ2.png

 

Kerbiloid is being facetious, but if that's really a problem there's no reason they can't start it on the arm at an angle so that it's traveling nose forward on exposure to air.

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On 11/26/2021 at 6:24 PM, Nuke said:

im shocked that the thing worked, at least the 1/3 scale model of thing. 

It's running at a tiny fraction of what you need for ballistic launch. This doesn't scale at all. A cannon launch is cheaper and way more practical in absolutely every single way, including requiring a lower acceleration for a much shorter duration, and we're not even doing these. I'm absolutely flabbergasted that this farce has been going on for this long. I can't imagine any remotely competent engineer signing off on this as anything beyond, "marginally plausible at a stretch." This simply has got to be a scam.

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1 hour ago, K^2 said:

It's running at a tiny fraction of what you need for ballistic launch. This doesn't scale at all. A cannon launch is cheaper and way more practical in absolutely every single way, including requiring a lower acceleration for a much shorter duration, and we're not even doing these. I'm absolutely flabbergasted that this farce has been going on for this long. I can't imagine any remotely competent engineer signing off on this as anything beyond, "marginally plausible at a stretch." This simply has got to be a scam.

I believe centrifugal machine guns have always been the poor man's gauss cannons and railguns.

But I also know that after that one guy began slapping spaceships together in a parking lot, I've learnt to have a little faith.

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25 minutes ago, DDE said:

I believe centrifugal machine guns have always been the poor man's gauss cannons and railguns.

Disagreed.

They were always the rich man's gauss cannons and railguns.

Enough rich to buy a washing machine with centrifuge just to spend it on the backyard star wars.

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1 hour ago, jimmymcgoochie said:

Why bother with the crazy spinny thing when you could just use a linear accelerator using magnets? Aside from accidentally frying your electronics, why wouldn’t a big railgun be a better option?

Think the main problem here is the capacitor bank needed. 10 tons up to mach 6 is an lot of energy. Rail guns are not mature enough I think and an coil gun has to be pretty long. 

Now an 30 degree launch angle is low, had in not been better to launch straight up and use control surfaces to tilt in upper atmosphere? 
The US army looked at the perfect way to guided shells for as long range as possible and found over 80 degree and this turn was most effective. 
It was some thought of an vertical firing gun as this would be lightweight but it could only fire smart shells and would not work at close ranges so you would still need an normal gun.

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10 hours ago, DDE said:

But I also know that after that one guy began slapping spaceships together in a parking lot, I've learnt to have a little faith.

You have a point, but solving fundamental physics problems tends to be an even less common occurrence than solving seemingly impossible business/process problems. Last instance which surpasses the challenges of spin launch is work by a certain patent clerk a century ago. Yeah, I'm that incredulous about the "engineering" challenges here.

7 hours ago, magnemoe said:

Think the main problem here is the capacitor bank needed. 10 tons up to mach 6 is an lot of energy. Rail guns are not mature enough I think and an coil gun has to be pretty long. 

We do have a proven method for doing this with chemical propulsion linear acceleration (aka canon), though. With just the pipe of the same length as the spin launch facility diameter, you can have a lower average acceleration over just seconds to get to the same velocity. And you don't have to de-spin the rocket after firing it out of a canon. Plus, even if you have to evacuate the chamber, which might not even be necessary, it's a much smaller volume, so you'd be able to do several launches an hour instead of (maybe) one per day with spin launch.

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