Spin Launch at Spaceport America.

[mura_gadi (Steve)]

https://www.youtube.com/watch?v=yrc632oilWo

Other things going on with Elon, interesting use of a centrifuge... great way to get water and raw materials up if they can get anything from the test trials.

Biggest slab of carbon fibre shown around the 5minute part.... the potential for an artillery piece though is scary.

[Visionary (David)]

As a military weapon, shrouded in plasma it would be mega stealthy

[mura_gadi (Steve)]

"Shrouded in plasma"... anything would be awesome.

But they're building a 10ton launcher to 75km vertically, a scaled down version to 2000 pounds and 45degrees would a game changing trebuchet.

The doors are pretty cool...

[ChrisD (Chris)]

they kind of trivialise the out of balance on release problems they face I think.

At the moment before release the projectile will weigh equivalent to 100K tons. That is the weight of the largest aircraft carrier on the planet. Before release it will be balanced by a counter weight providing an equal 100k tons on the other end of the arm.

On release the system will instantaneously be 100k tons out of balance.The impulse forces generated on the mechanism and bearings are unimaginable.
One plan is to release the counter weight into your launch facility at the same time to maintain balance. However, now you have to capture/contain a 10 ton mass travelling at mach 6. You're going to need something better than some foam and a net.

[mura_gadi (Steve)]

A high tech water bottle counter weight would be cheap enough for single use, if the arm can survive a 1/2 rotation, the counter weight could be ejected within milliseconds of the payload.

Interesting ballistics testing for the trial and a heck of a kinetic blast if the timing is out...

[ChrisD (Chris)]

Originally Posted by mura_gadi

A high tech water bottle counter weight would be cheap enough for single use, if the arm can survive a 1/2 rotation, the counter weight could be ejected within milliseconds of the payload.

Interesting ballistics testing for the trial and a heck of a kinetic blast if the timing is out...

Rough calculation indicates that the counterweight will be carrying an kinetic energy of around 21 GigaJoules at release.

That's equivalent to the detonation of around 5 tons of TNT, or enough energy to power 17 DeLoreans back to the future.

How do you handle that safely?

[mura_gadi (Steve)]

The counter weight carries deployable fins for slowing and guidance, enough for a parachute at some stage after launch. There is no fuel or payload so you have heaps of space to vary the counter weight.

You could treat it like a guided bomb ... and plenty of parts for those on production lines to keep prices low.

[ChrisD (Chris)]

Ah, I see what you're saying. You want the counterweight to stay on the arm for another 180° of rotation and then released on the upswing.

I just cant conceive of any structure could survive the impulse forces of 100,000 tons out of balance while we wait to get that upswing release of the counterweight.

The only way for the arm to survive would be to release both the projectile and the counterweight at the same instant. The projectile goes up and the counterweight goes down. This is the engineering problem I wouldn't want to be responsible for solving.

[mura_gadi (Steve)]

Yeah, its a problem... I woke with the thought you may as well launch in pairs over a counter weight.

The thought of simultaneous release has a very large problem in a vertical launch, the pit for the downward trajectory blast being one...

But Elon certainly has shown he can hire the right people for the projects and he can run large scale testing at comparatively low market costs.

*************

A rocket that can hold high altitude would be a major part in any sky elevator project. If you can fling that rocket to 75km, it only needs enough fuel for maintaining altitude and some course corrections to allow hooking onto the sky crane and get the payload to load space.

Such a system would see space hardware/resupply launch costs reduced pretty dramatically.

International Academy of Astronautics published "Road to the Space Elevator Era", seems to suggest is closer than nuclear fusion at least.