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Spin Launch Tethered Missiles.... In Space?


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It dawned on me that tethering up a missile and spinning it for an hour at 1g would allow a spacecraft to launch it at ludicrous speeds that the missile could never achieve on it's own nearly as quickly (ion drive would take months/years lol).

 

Since space combat IRL involves a lot of lead time anway.... if in space and not mere low orbit, I think spin launching from tethers could compete with and even outperform railguns and coilguns.

 

Pros: Much higher end velocity of missile or projectile launched.

Cons: Takes longer to reload and fire  I also presume NOT spinning up the entire spacecraft in the opposite direction as the tether is spun will becone problematic. If this can be overcome without wasting a lot fuel via thrusters let me know. I presume high mass could do it even though that makes the spacecraft a lumbering cow.

Suggested prime uses: I think it is ideal for moon bases, both because they won't worry about counter spin and that they could install many for cheap but effective launching.

 

Spaceships could also employ them if they have a lot of lead time.

Edited by Spacescifi
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That restricts you to launch only in the plane of rotation. As for it being a cheap and effective system, have you seen the size of the Spinlaunch baby facility? Have you compared the forces involved?

Spinning the entire spacecraft can not be overcome by adding mass to the spacecraft (at least not in a sense that it would require less fuel to stop it from spinning).

A conventionally launched rocket can be aimed in arbitrary direction and still maintain high enough acceleration to be formidable.

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25 minutes ago, Shpaget said:

That restricts you to launch only in the plane of rotation. As for it being a cheap and effective system, have you seen the size of the Spinlaunch baby facility? Have you compared the forces involved?

Spinning the entire spacecraft can not be overcome by adding mass to the spacecraft (at least not in a sense that it would require less fuel to stop it from spinning).

A conventionally launched rocket can be aimed in arbitrary direction and still maintain high enough acceleration to be formidable.

 

Tethers in space will make size less an issue.

Spin launch on earth is fighting atmosphere and gravity. Space won't have that problem.

 

I think you are saying that spinning up the entire spacefraft is unavoidable.

If that is so then perhaps it would ve vest used for moon bases as I suggested.

 

Tethere are less bulky than spin launch although more fragile.

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9 hours ago, Spacescifi said:

Tethers in space will make size less an issue.

Have you done some basic math? What are the forces in the tether, for any reasonably short tether?

9 hours ago, Spacescifi said:

I think you are saying that spinning up the entire spacefraft is unavoidable.

Conservation of momentum is a law. You either use rockets to accelerate the missile, or to despin the spaceship.

As for moon base, you still only can shoot in one plane, which makes it rather useless as a weapon, since all you need to do to avoid this missile is to move out of that particular plane.

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22 minutes ago, Shpaget said:

Have you done some basic math? What are the forces in the tether, for any reasonably short tether?

Conservation of momentum is a law. You either use rockets to accelerate the missile, or to despin the spaceship.

As for moon base, you still only can shoot in one plane, which makes it rather useless as a weapon, since all you need to do to avoid this missile is to move out of that particular plane.

 

Missiles can maneuver so it is not useless.

8 hours ago, DDE said:
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We're back to basics, eh?

scale_1200

 

 

Essentially.... kind of?

With rocket missile upgrades.

War has been more or less the same anyway.

It's just the arrows became a lot faster and also self guided.

 

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6 hours ago, kerbiloid said:

And rotate it by rockets.

While that would solve all of the issues involving action & reaction it would also obliterate the whole point of launching this way (no need for reaction mass) in the first place.

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7 hours ago, Kerbart said:

While that would solve all of the issues involving action & reaction it would also obliterate the whole point of launching this way (no need for reaction mass) in the first place.

You got it.

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8 hours ago, Spacescifi said:

It's just the arrows became a lot faster and also self guided.

The arrows have eyes now. Tension catapults are mostly used for drones.

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19 hours ago, Spacescifi said:

I think you are saying that spinning up the entire spacefraft is unavoidable.

If that is so then perhaps it would ve vest used for moon bases as I suggested.

 

Tethere are less bulky than spin launch although more fragile.

Spinning up the spacecraft is not unavoidable. It does require active measures to prevent though. Rockets or reaction wheels can counter spin. A massive reaction wheel accelerating opposite way from the shot should work, definitely would work well enough for a fictional setting. After release set up the next shot rotating the other way and counter the spin by decelerating the now very fast rotating reaction wheel. Oh and don't plan on maneuvering while that wheel is going - gyroscopic forces from something massive enough will make turning quite impossible without massive propellant expenditure.

But your aim is still limited to intercept points near the plane of rotation. Missiles' maneuvering ability and distance to intercept determine how far off plane you can target. Probably not practical for low orbit ship-to-ship scenarios unless you limit your vehicles to very slow accelerations. If time to spin up a shot is much shorter than time to perform a meaningful plane change then it could work. Interplanetary distances, where travel mostly happens near the ecliptic, could also work. And a huge constellation of orbital defence satellites around a fortified planet could have shots ready on so many planes pretty much any approach can be targeted. They cannot concentrate their fire though.

Tether behaviour after release is also a concern. It isn't really a viable weapon if, after release, the tether proceeds to wrap itself around your ship and crush it like a soda can. It may be necessary to release the tether into the void too. That will increase the cost of a shot and add a danger to navigation. Latter can become a plot device though, if a random ship damaging event is needed.

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9 hours ago, Spacescifi said:

Missiles can maneuver so it is not useless.

Do the math. See at what angle off the plane it no longer makes sense to use this system.

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interesting concept for planet-to-planet conflict. Think Mars vs Earth. Most infrastructure will be in orbit, so in a 'fixed' place. The spinnlauncher would be the equivalent of continental ballistic missels. 

You have a somewhat massive satellite. One ring with tethers with rockets on the end (10-12 maybe). a counter rotating weight. Spinn up while your planet is blocking observation and release. Since the missels are not using their engines you have basicly a 'stealth' launch. Or at least stealthier. 

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This is not feasible for several reasons. Spinning something at 1g (acceleration on the projectile, I think you mean?) would rapidly create centrifugal force sufficient to break any conceivable tether material. And would require a massive amount of energy. And respecting Newton's third law, the launcher would be thrown backward with as much force as the projectile has going forward. which the launcher would then have to counter-act somehow so that it's not just thrown willy-nilly around the solar system. It would be much simpler to just fire the rocket in a conventional way. 

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3 hours ago, kerbiloid said:

SSTO spin launcher.

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https://www.dvaveka.ru/raznoe/igrushki/detskaya-igrushka-letayushchiy-vertolyot-fabrika-igrushek-yunost-leningrad-1968-g/

68076.1000x0.JPG

Stick inside and quicly pull out the cord to start the propeller rotating.

 

 

 

 

Bigger launcher - bigger craft,

You’d need to pull the cord pretty fast though - do you think that tying it to a rocket would work?

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On 6/1/2022 at 6:17 AM, Shpaget said:

That restricts you to launch only in the plane of rotation. As for it being a cheap and effective system, have you seen the size of the Spinlaunch baby facility? Have you compared the forces involved?

Spinning the entire spacecraft can not be overcome by adding mass to the spacecraft (at least not in a sense that it would require less fuel to stop it from spinning).

A conventionally launched rocket can be aimed in arbitrary direction and still maintain high enough acceleration to be formidable.

One hour at 1g = 32,400m/s, an absolutely ludicrous speed (.0001c), to the point that the elliptical would no longer be of interest and you are heading well out of the solar system.  This implies a more or less single use shot (unless you are breaking your interstellar craft into pieces and then reassembling them while starting the journey), which doesn't make sense.  A 1km teather would have 10 million Gs of acceleration, essentially impossible.  a2000km teather (the Moon has a 1800km radius) would only knock that down to 50,000 gees.  This is beyond E. E. Doc Smith tech.  Spinning and linear rails have roughly the same issues and the vehicles have to sustain the same amount of acceleration, even though the spin launcher doesn't have to supply the acceleration itself (except the spinners also have to deal with the sudden momentum delta once the vehicle is released).

Building a spinner on the Moon capable of launching to Mars, the asteroid belt, Venus, or even Jupiter (the gravity assists from Jupiter will get you anywhere in the Solar System, even the  Sun) might make sense (but will require a huge tether and have limited planes).  Going interstellar is just not going to happen.  Even going within the solar system, you get plane of rotation issues.  You'd have to build near the poles of the Moon and then you'd have a limited window twice a month when you are pointed in the elliptical (make sure that you have two windows to launch, Spin launch obviously only uses one).  No idea how long those windows are open, nor how tight an angle you'd need (expect to need maneuvering rockets no matter how accurately you can throw).

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