Space catapult startup SpinLaunch comes out of stealth

Re:Space catapult startup SpinLaunch comes out of stealth by danbruc on Thursday February 22, 2018 @06:49PM (#16442736)

Even ignoring air resistance, if your hypothetical spacecraft centrifuge had a radius of one mile, then the spacecraft would still experience 114 g at 3000 miles per hour. If you more realistically spun up Apple's new headquarter with a diameter of 461 meters [1] to one revolution per second, that makes 3240 miles per hour, the spacecraft and the outer wall of your centrifuge would experience a centripetal acceleration of 928 g. Not going to happen. And 3000 miles per hour is also pretty slow, about half the speed in a geostationary orbit, for a low earth orbit you need about 17,500 miles per hour [2] which is almost 6 times faster and would increase the forces 36 times.

[1] https://en.wikipedia.org/wiki/Apple_Park

[2] https://en.wikipedia.org/wiki/Orbital_speed

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Re:Space catapult startup SpinLaunch comes out of stealth by danielbarla on Friday February 23, 2018 @03:15AM (#16444945)

Those orbital numbers are sobering, but there may still be plenty of reason to investigate a launch mechanism where the "fuel" comes from an external source.

I haven't run the numbers, but a quick look at typical delta-V budgets [1] (which calculate atmospheric losses as 1.5 to 2 km/s of delta-v), if one could accelerate something fast enough that it escapes most of Earth's atmosphere (and only then burn for orbital velocity), you'd be saving ~17 to 20% on the delta-v requirements. Due to the nature of the Tsiolkovsky equation, that could be a very substantial saving.

That said, I'm also wondering why a centrifuge would be better than say, some kind of low pressure tube / rail, but I'm sure these guys have done their maths and believe in it.

[1] https://en.wikipedia.org/wiki/Delta-v_budget

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Re:Space catapult startup SpinLaunch comes out of stealth by nine_k on Friday February 23, 2018 @10:31AM (#16446889)

Scaled Composites tried to solve it by launching from a winged aircraft. (Too bad they seem to have stopped.)

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Re:Space catapult startup SpinLaunch comes out of stealth by stcredzero on Friday February 23, 2018 @01:34AM (#16444655)

Even ignoring air resistance, if your hypothetical spacecraft centrifuge had a radius of one mile, then the spacecraft would still experience 114 g at 3000 miles per hour

We can build electronic components that are rated for 100000 g's. I think craft that can withstand 10's of g's are within our capability to build. Why not make the circle the size of the LHC? Why not larger?

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Re:Space catapult startup SpinLaunch comes out of stealth by anonytrary on Friday February 23, 2018 @02:17AM (#16444787)

It's about the payload. It is also accelerating. It would be flattened to a crisp.

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Re:Space catapult startup SpinLaunch comes out of stealth by stcredzero on Friday February 23, 2018 @02:25AM (#16444803)

Anything like this should be assumed to be launching bulk payloads or hardened payloads. For machines 10's of g's is not that big a deal. It's challenging, but quite doable. For lots of kinds of bulk cargo, it's not a big deal.

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Re:Space catapult startup SpinLaunch comes out of stealth by anonytrary on Friday February 23, 2018 @03:22AM (#16444966)

Yeah, I'm sure certain restricted types of cargo may be launched this way. We will still need rockets for the vast majority of cargo types.

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Re:Space catapult startup SpinLaunch comes out of stealth by miketery on Thursday February 22, 2018 @08:13PM (#16443308)

Out of curiosity is it correct to assume launch at the equator going east adds 24,000 miles circumference / 24 hrs = ~1000mph

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Re:Space catapult startup SpinLaunch comes out of stealth by andbberger on Thursday February 22, 2018 @10:36PM (#16443992)

Yes.

That's ~1000mph less delta-v needed to reach orbit. But note that the air is also moving in the same rotating frame, so there is no difference in air resistance upon exit from the launcher whether you are going east or west.

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