Can we throw a rocket into (near) space?

"davesaddiction @ opposite-lock.com" (davesaddiction) 01/29/2020 at 15:44 • Filed to: None

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“ A centrifuge large enough to contain a football field will whip a rocket around in circles for roughly an hour , its speed steadily ramping up to more than 5,000 mph . The vehicle and its payload—up to 200 pounds’ worth of satellite—will experience forces that, at their peak, will be ten thousand times stronger than gravity . Once it’s spinning at launch spee d, the centrifuge will release the rocket and send it screaming into the stratosphere. At the threshold of the cosmos, it will fire its engine for a final nudge into orbit.”

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PartyPooper2012 > davesaddiction @ opposite-lock.com 01/29/2020 at 15:56

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Embiggened version of this might also work

vondon302 > davesaddiction @ opposite-lock.com 01/29/2020 at 15:58

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Im dizzy just thinking about it.

TheTurbochargedSquirrel > davesaddiction @ opposite-lock.com 01/29/2020 at 16:06

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I want to be nowhere near that when it is running. Flywheels are damn scary.

RallyWrench > davesaddiction @ opposite-lock.com 01/29/2020 at 16:07

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I t seems to me that accelerating something weighing at least several hundred pounds to 5,000mph in a 300 foot diameter circle... isn’t going to work. The force that the rocket & payload would have to withstand is way, way more than that of just launching it normally. They basically admit that. So it will have to be built to withstand that force before it ever leaves the ground, which adds structural weight, which effectively reduces the actual payload and makes it harder to accelerate, which makes it harder to launch , which etc etc. Can you imagine the rocket’ s fuel system withstanding that and then firing correctly ? I mean, I’m not an engineer, but I did stay at a Holiday Inn Express last night...

I should just say that I encourage them to try. It’ll make for fun videos. 

davesaddiction @ opposite-lock.com > TheTurbochargedSquirrel 01/29/2020 at 16:08

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No joke...

davesaddiction @ opposite-lock.com > RallyWrench 01/29/2020 at 16:11

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Very good points!

Stapleface-Now Hyphenated! > davesaddiction @ opposite-lock.com 01/29/2020 at 16:28

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Seems like a really neat theory.  But I wonder about the what ifs. What if this thing launches prematurely or at the wrong angle. Then you have a multi ton misssle being launched at 5,000 mph. Just seems like a bad idea.

ClassicDatsunDebate > davesaddiction @ opposite-lock.com 01/29/2020 at 16:35

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so basically, th e thing you are slingshotting has to withstand the energy of an entire fuel payload required to break free of earths gravity, all at once.

zipfuel > davesaddiction @ opposite-lock.com 01/29/2020 at 16:39

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I saw articles about this and really want to compare it to the various projects that tried to use a very large cannon to launch small satellites.

https://en.m.wikipedia.org/wiki/Space_gun

The most interesting rabbit hole of which is Gerald Bull and the Iraqi super gun which he was developing before (probably) the Israelis whacked him.

https://en.m.wikipedia.org/wiki/Gerald_Bull

Although project HARP is cool because that gun is still there just south of the airport in Barbados.

I gotta do a full Oppo post on this

davesaddiction @ opposite-lock.com > zipfuel 01/29/2020 at 16:42

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Yes, you do.

davesaddiction @ opposite-lock.com > ClassicDatsunDebate 01/29/2020 at 16:42

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Pretty much.

davesaddiction @ opposite-lock.com > Stapleface-Now Hyphenated! 01/29/2020 at 16:43

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Oh yeah, there’s lots of ways this can go really wrong.

3point8isgreat > RallyWrench 01/29/2020 at 16:45

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That 10,000 G’s thing would definitely destroy most stuff we want to put into space.

Also all that to only get to 5,000 MPH when LEO is 17,000+ MPH . That “Final nudge into orbit” is actually the majority of the acceleration needed.  And I don’t see many 200lb payloads having the fuel load necessary to get that additional 12,000 MPH.

Only Vespas... > zipfuel 01/29/2020 at 17:08

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Do a full piece...I hunted down his abandoned factory near Jay Peak up in Vermont before it “burned down”.  Fascinating story.

Distraxi's idea of perfection is a Jagroen > ClassicDatsunDebate 01/29/2020 at 17:17

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No, the kinetic energy (what the fuel would supply to a rocket) is fed i n pretty gradually - it accelerates over an hour or so. My guess is that’s the main attraction o f this system - stretching the energy input out brings the power need down to somethi n g a decent sized electric motor can supply.

The high G loads come from the fact that it’s going at 5000mph in a small circle rather than a straight line - it’s pulling 10,000G side loads round a very long corner , effecti ve ly (which puts F1 car’s cornering into perspective) . There’s no actual energy involved in that, just l ike there’s no energy involved in the 1G that attaches you to the floor. Just lots of sideways force trying to flatten the payload into a smear on the outside of the hull.

Distraxi's idea of perfection is a Jagroen > davesaddiction @ opposite-lock.com 01/29/2020 at 17:29

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My big question f ro m th is is what are they doing with the counterweight? They talk about simultaneously releasing a counterweight when they release the payload, to keep the centrifuge balanced. L eaving aside that the “simu ltaneously” is going to need to be pretty darn accurate since we’re talking about 20 million lbf of unbalance, if the payload is travelling upwards at release, the counterweight is travelling downwards . So now you’ve got a mass with enough kinetic energy to get to space - basically a Rod from God - heading for the ground below your big, rapidly-spinning   centrifuge Dissipating that sort of energy without causing vibration that will sh ake your centrifu g e apart will be ...in te resting... I suspect. Maybe if you fire the payload near-horizontal, and site your centrifug e on an island ( like a good supervillain should), you can just drop the counterweight into the sea, but that his its own implications.

Chariotoflove > davesaddiction @ opposite-lock.com 01/29/2020 at 17:32

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Not taking your thread lightly, but this does remind me of the birth centrifuge . The inventor was awarded an   Ig Nobel Prize .

Just Jeepin' > davesaddiction @ opposite-lock.com 01/29/2020 at 17:58

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Reminds me of a recent YT video I enjoyed and then got sad because while we could do it today, we absolutely won’t.

feather-throttle-not-hair > davesaddiction @ opposite-lock.com 01/29/2020 at 18:14

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Uncle Rico could.

Back in high school though. Not anymore.

davesaddiction @ opposite-lock.com > Just Jeepin' 01/29/2020 at 18:59

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Very cool. 

davesaddiction @ opposite-lock.com > feather-throttle-not-hair 01/29/2020 at 18:59

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Ha!

davesaddiction @ opposite-lock.com > Chariotoflove 01/29/2020 at 18:59

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Ha!

ClassicDatsunDebate > Distraxi's idea of perfection is a Jagroen 01/29/2020 at 19:40

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The only thing providing the energy required to launch the payload is the centrifuge arm. At the moment it’s released, it is being acted upon by all the energy required to get it into orbit (apparently not according to 3point8isgreat  comments above) .  It can’t get anymore so it has to be able to handle all of it at once, regardless how the force was applied.  A rocket imparts the same amount of energy but over time, that’s why the peak force applied is way les than what this thing would have to apply.  That’s what I was getting at.  Maybe we’re saying the same thing.

zipfuel > Only Vespas... 01/29/2020 at 19:46

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Oh I just looked that up on Google maps, more derelict giant gun bits in the woods - awesome

TheRealBicycleBuck > davesaddiction @ opposite-lock.com 01/29/2020 at 19:53

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Reminds me of the Slingatron . Instead of a centrifugal arm, it would use a spiral ramp with gyrating motion to accelerate the payload. There was a kickstarter campaign for it, but they failed to meet their funding goal. https://www.kickstarter.com/projects/391496725/the-slingatron-building-a-railroad-to-space

The slingshot guy built a small one powered by a drill, but his uses a pusher arm instead of gyration to accelerate the ball.

zipfuel > Distraxi's idea of perfection is a Jagroen 01/29/2020 at 20:00

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The thing is, to avoid everything getting very exciting in there the counterweight has to let go at the exact time as the payload meaning it’s going straight down

just-a-scratch > PartyPooper2012 01/29/2020 at 20:37

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How fast can a wave propagate in an elastic band?

Distraxi's idea of perfection is a Jagroen > zipfuel 01/29/2020 at 21:01

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Not necessarily. You don’t have to launch vertically to get to space. Rockets do bec au se it’s the most efficient strategy if you’re carrying 100% of your own fuel and therefore want to minimise the amount of it you waste pushing though atmosphere. It’s always going to be necess ary for the projectile to have some fuel to do an orbital injection burn, but the launch angle which minimises the size of that burn is actually horizontal - basically at a tangent to the earth’s curvature. That’s also the most efficient launch angle overall if you don’t have atmosphere to worry about.

Given that for these guys most of the energy is imparted at launch and is therefore cheap, whereas the injection burn comes from fuel which has to be carried and is therefore expensive, it may be that minimising a tmospheric drag isn’t the dominant factor for them. With all the variables involved the math’s going to get complicated, but it wouldn’t surprise me to fi nd them launching at an angle . Maybe a long way off vertical, if deal ing with the counterweight pro blem actually turns out to be the dominant engineerin g challenge....

Distraxi's idea of perfection is a Jagroen > ClassicDatsunDebate 01/29/2020 at 21:24

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No, I don’t think we are. Your analogy would be valid if it was a slingshot or a bow, where as soon as you let go all the stored energy gets applied violently to the projectile. But in this instance the energy isn’t stored in the ce ntrifuge and applied at release , it’s directly and gradual ly applied to the projectile as the centrifuge spins up . By the time you let go it’s alre ady going a s fast as it needs to, there’s no extra energy applied. I f you unwrapped the 100 ,000 (or whatever) laps of the centrifuge it makes during spin-up into a straight line, it’d be a nice gentle acceleration path - much more gentle than a rocket, since they’re saying the’ll spend an hour getting up to speed where a rocket only takes a couple of minutes.  

The forces come from the fact that it’s going in circles - release has nothing to do with it. If you spun the centrifuge up and then let it coast back down without ever letting go of the projectile, the peak Gs the projec tile sees would still be the same, bec au se they’re just the centrifugal force.

415s30 W123TSXWaggoIIIIIIo ( •_•))°) > davesaddiction @ opposite-lock.com 01/29/2020 at 21:50

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I think a long track in the desert for a rail gun type of system would be easier. 

415s30 W123TSXWaggoIIIIIIo ( •_•))°) > Just Jeepin' 01/29/2020 at 21:51

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We do need a space elevator to get anything done up there. 

ClassicDatsunDebate > Distraxi's idea of perfection is a Jagroen 01/29/2020 at 22:08

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Agreed. BUT the centrifuge has to release the energy all in one instance. It’s stored up the total energy (s tored in those 10,000 G s) and then it releases the projectile. A rocket would never see 10,000 Gs at one time, it’s spread over the time it takes to get to orbit.

It’s the same as an arrow or a bullet. The reason the centrifuge takes so long to ramp up is the HP (torque) limitation of the drive on the flywheel, not because it’s more gentle.  In the end, just before release, it’s applying 10,000 G’s of force to the projectile.

Distraxi's idea of perfection is a Jagroen > ClassicDatsunDebate 01/29/2020 at 22:18

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No, it’s not. It’s exactly   the same as accelerating your car in circles then straightening the wheel once you’re at your cruising speed . You’re basically saying that all the energy of the accel eration is stored in your steeri ng system and then returned to the car at the instant you straighten the whee l.

All that releasing the projectile from the centrifuge does is remove the cornering force, letting the projectile c ha nge from going in circles to going in a straight line. There’s zero energy transfer from centrifuge to projectile at the mom ent of release.

ClassicDatsunDebate > Distraxi's idea of perfection is a Jagroen 01/29/2020 at 22:38

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Force is force. (The amount of force needed to get the projectile into space) Mass is mass (the projectile)

Distance is distance(ground to space)

The same mass will take the same amount of work to get from the ground into orbit.

Work is force x distance. The centrifuge must apply all the force required in one instant, as it lets go of the projectile. Rocket engines can apply its force over a huge distance therefor the force is way less on the rocket.

If you think for a moment that the centrifuge object requires 10,000Gs to get it to orbit and a rocket sees 3Gs, it may make more sense. Think of the projectile on the flywheel as potential energy and the rocket engine as potential energy. Now think about how much time each one has to add force to the work. One is instantaneous and one is over time.

The distance travelled in the centrifuge doesn’t count to the work.

Distraxi's idea of perfection is a Jagroen > ClassicDatsunDebate 01/29/2020 at 22:56

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I think we might have to agree to disagree on that one. Fortunately, AFAIK neither of us ha ve im me diate plan s to build a huge centrifuge and launch shit into space. Or i s that a MWAHAHAHAHA I hear?

ClassicDatsunDebate > Distraxi's idea of perfection is a Jagroen 01/29/2020 at 23:25

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agreed.  I’ll keep the huge centrifuge building to the start-up snake oil salesmen...lol.

415s30 W123TSXWaggoIIIIIIo ( •_•))°) > zipfuel 01/29/2020 at 23:31

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PartyPooper2012 > just-a-scratch 01/30/2020 at 06:14

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pretty darn

Only Vespas... > zipfuel 01/31/2020 at 19:51

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It’s in that grey border area before walls  between countries. A hillside was used to support the gun’s elevation. From a distance the clearing in the woods looks just like ano ther ski run.