Author Topic: Spinlaunch... Can it succeed?  (Read 82992 times)

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Offline Rick Law

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Re: Spinlaunch... Can it succeed?
« Reply #50 on: November 24, 2021, 09:14:22 pm »
...
Regarding rail guns. Rail guns don't work, at least not practically, and even the US military is on the verge of totally giving up on that technology.

Rail gun has a demonstrated velocity of around mach 7 by the US Navy.  Mach 7 is around 2.3km/s and is around Spinlauch's planned launch speed.  So while rail gun may not be suitable to be carried around by ships yet, it is certainly feasible for a fix-located rail gun to get to mach 7 exit velocity.

Rail-gun space launch has been proposed by NASA - mach 10 launch speed of a scram jet to complete the journey into low orbit space. 

Spinlaunch is proposing a 100 meter spinning diameter, so we use 100 meter rail gun as base comparison.   Remember the equation I posted in an earlier reply: linear acceleration is V2/2L whereas centrifugal acceleration is V2/R.  R is 1/2 the diameter, so 100 meter linear will have 1/4 the linear g verses spinning centrifugal G.

A much longer rail gun will reduce acceleration G force as well as decrease the power needed for acceleration.  Power is proportional to square of current, so a 10x increase in rail gun length will reduce electrical current need by 100.  10x that length to a 1km rail.  1km rail reduces electrical current need down to 1/100 that of a 100 meter rail.    With 1km rail, the G force is down to 1/40 of centrifugal G of a 100 meter diameter spinner.

But, as already pointed out by mfro's reply, mach 7 is less than 1/3 the escape velocity.  Add air drag to that equation, and air drag is proportional to the square of velocity, I am doubtful that an object with exit velocity at mach 7 can even reach 29,000 feet (height of Everest where air is too thin for human).  1/40 of 10000g (=250g) is still a lot of g's, and we are still talking only mach 7.  So problems are aplenty to actually get it into orbit, spinning or linear.

Reference:
Navy rail gun mach 7 demo video:
« Last Edit: November 24, 2021, 09:22:18 pm by Rick Law »
 

Offline bdunham7

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Re: Spinlaunch... Can it succeed?
« Reply #51 on: November 24, 2021, 10:01:56 pm »
I am doubtful that an object with exit velocity at mach 7 can even reach 29,000 feet (height of Everest where air is too thin for human). 

Garden-variety artillery with muzzle velocities under Mach 3 can reach over 50,000 feet altitude. 
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Offline m98

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Re: Spinlaunch... Can it succeed?
« Reply #52 on: November 24, 2021, 11:27:08 pm »
Since you're such an expert, perhaps you could explain why Thunderfoot is wrong, using the relevant mathematics and physics?
He is not wrong with his calculations, it's just that the publicly available data he used isn't enough for any meaningful analysis. Yes there is high acceleration on the launch vehicle by principle and they appeared to have stability problems on their very first test. Which set of axioms state that one cannot possibly solve those issues? Satellites that survive such high-g launchers are not an entirely new thing and have already been studied.
What else was there? I don't think Saddam Hussein competing on the space launcher market will be a reasonable concern anytime soon. And liquid-propellant engines that can ignite in microgravity are used on satellites all the time.

Just see Thunderfoot vs. Space X. Uniquely the only scam company in the world to successfully operate a manned space program.

...
Regarding rail guns. Rail guns don't work, at least not practically, and even the US military is on the verge of totally giving up on that technology.

Rail gun has a demonstrated velocity of around mach 7 by the US Navy.  Mach 7 is around 2.3km/s and is around Spinlauch's planned launch speed.  So while rail gun may not be suitable to be carried around by ships yet, it is certainly feasible for a fix-located rail gun to get to mach 7 exit velocity.

You have probably missed the news. https://www.thedefensepost.com/2021/07/08/us-navy-railgun/
Basically, huge money sink that never started to work reliably.
 

Offline Rick Law

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Re: Spinlaunch... Can it succeed?
« Reply #53 on: November 24, 2021, 11:55:58 pm »
I am doubtful that an object with exit velocity at mach 7 can even reach 29,000 feet (height of Everest where air is too thin for human). 

Garden-variety artillery with muzzle velocities under Mach 3 can reach over 50,000 feet altitude.

You are right.  My statement is wrong.  I was thinking no bullet will reach that altitude forgetting the fact that bullets has too little mass to carry enough energy.

I stand corrected.

...
You have probably missed the news. https://www.thedefensepost.com/2021/07/08/us-navy-railgun/
Basically, huge money sink that never started to work reliably.

I am not claiming that rail gun works for the Navy.  I am saying that as a proof of concept, rail guns already demonstrate that it can shoot at mach 7, reliably or otherwise.

Rail guns or spinning wheel both need work.  A 100 meter rail shooting upward is one thing, 10x to a 1km high vertical rail gun will need huge amount of work to make into reality, if ever.

These are in the reams of dreams.   May be it will work, may be it wont.
 

Offline Haenk

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Re: Spinlaunch... Can it succeed?
« Reply #54 on: November 25, 2021, 08:58:27 am »
Which set of axioms state that one cannot possibly solve those issues?

https://de.wikipedia.org/wiki/Str%C3%B6mungswiderstand

Note the v square, which is a pretty effective way to not be able to easily reach escape speed plus creating enormous heat (turning the drag into heat, which will probably melt wolfram and ceramics).
The slingshot method requires having escape speed plus losses due to drag at start in the densest medium. I assume a nice fireball, when then projectile vaporizes on exit, hitting air.
A rocket will slowly (in comparison) reach the escape speed - and that's in the least dense medium (downside: it has to carry its fuel).
 
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Offline thinkfat

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Re: Spinlaunch... Can it succeed?
« Reply #55 on: November 25, 2021, 09:15:19 am »
Which set of axioms state that one cannot possibly solve those issues?

https://de.wikipedia.org/wiki/Str%C3%B6mungswiderstand

Note the v square, which is a pretty effective way to not be able to easily reach escape speed plus creating enormous heat (turning the drag into heat, which will probably melt wolfram and ceramics).
The slingshot method requires having escape speed plus losses due to drag at start in the densest medium. I assume a nice fireball, when then projectile vaporizes on exit, hitting air.
A rocket will slowly (in comparison) reach the escape speed - and that's in the least dense medium (downside: it has to carry its fuel).

Plus they cannot afford to put heavy heat shielding on a small launch vehicle that is supposed to be mostly payload.
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Offline Nusa

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Re: Spinlaunch... Can it succeed?
« Reply #56 on: November 25, 2021, 01:16:38 pm »
Which set of axioms state that one cannot possibly solve those issues?

https://de.wikipedia.org/wiki/Str%C3%B6mungswiderstand

Note the v square, which is a pretty effective way to not be able to easily reach escape speed plus creating enormous heat (turning the drag into heat, which will probably melt wolfram and ceramics).
The slingshot method requires having escape speed plus losses due to drag at start in the densest medium. I assume a nice fireball, when then projectile vaporizes on exit, hitting air.
A rocket will slowly (in comparison) reach the escape speed - and that's in the least dense medium (downside: it has to carry its fuel).

Plus they cannot afford to put heavy heat shielding on a small launch vehicle that is supposed to be mostly payload.

Luckily, they are only aiming for a much lower orbital speed, not escape speed. Also, the spinlaunch is only supposed to replace the first stage...the second stage for controlled orbital insertion would be rocket-based, after discarding the heat-soaked shell. At least as I understand their minimal FAQ.
 
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Offline PlainName

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Re: Spinlaunch... Can it succeed?
« Reply #57 on: November 25, 2021, 07:15:08 pm »
Quote
perhaps you could explain why Thunderfoot is wrong

He doesn't have to be wrong - the click-bait hyperbole is sufficient.

And for that reason, amongst others, I couldn't tell you about this video because I won't go near it. However, he's had dodgy ideas in  previous ones, setting up strawmen so he can knock themblow them up for more clicks.
 

Offline PlainName

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Re: Spinlaunch... Can it succeed?
« Reply #58 on: November 25, 2021, 07:18:29 pm »
Just a small point...

Quote
Spinlaunch is proposing a 100 meter spinning diameter, so we use 100 meter rail gun as base comparison.

doesn't square up with

Quote
A much longer rail gun will reduce acceleration G force as well as decrease the power needed for acceleration.

It's a bit of a false comparion, I think :)
 

Offline bdunham7

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Re: Spinlaunch... Can it succeed?
« Reply #59 on: November 25, 2021, 08:12:24 pm »
I assume a nice fireball, when then projectile vaporizes on exit, hitting air.
A rocket will slowly (in comparison) reach the escape speed - and that's in the least dense medium (downside: it has to carry its fuel).

It will get hot and perhaps require an ablative shield, but will be out of the lower atmosphere in seconds.  Sprint ABM missiles exceeded Mach 10 in the lower-to-mid atmospheric ranges where they operated. I'm sure they got hot.
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Re: Spinlaunch... Can it succeed?
« Reply #60 on: November 25, 2021, 11:53:27 pm »
I can't do mechanical engineering to save my life, but my spidey sense tells me this is not going to scale up.
The end result will go something like this:




 

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Re: Spinlaunch... Can it succeed?
« Reply #61 on: November 26, 2021, 12:00:57 am »
What would the centripetal g force on the payload be compared with simply shooting it out of a very large gun pointed skyward?

It would be interesting to know if it's possible to fire a rocket from a gun barrel and then have it ignite when it reached apogee.
 

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Re: Spinlaunch... Can it succeed?
« Reply #62 on: November 26, 2021, 12:08:51 am »
Since you're such an expert, perhaps you could explain why Thunderfoot is wrong, using the relevant mathematics and physics?
He is not wrong with his calculations, it's just that the publicly available data he used isn't enough for any meaningful analysis. Yes there is high acceleration on the launch vehicle by principle and they appeared to have stability problems on their very first test. Which set of axioms state that one cannot possibly solve those issues?

Didn't his numbers indicate that they are only currently at 1% of their required value or something?
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Offline PlainName

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Re: Spinlaunch... Can it succeed?
« Reply #63 on: November 26, 2021, 12:21:33 am »
Seems to me the biggest problem is letting go of the payload, not because it will burn up but because of the sudden unbalancing of the spinner. The video Dave posted illustrates the issue pretty well - in most of the windmill destructions I've seen, one arm lets go and the shock of that breaks the other two arms which then let go in sympathy.

But... what if that doesn't matter? When they used to launch rockets I bet no-one ever said "No, this will never work because the first stage won't survive coming down." Losing most of the rocket is just the cost of doing business (or used to be). So what if the destruction of the wheel is just the cost of this style of launching?

Against that, it would be a pretty spectacular loss of functionality...
 

Offline bdunham7

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Re: Spinlaunch... Can it succeed?
« Reply #64 on: November 26, 2021, 12:35:37 am »
It would be interesting to know if it's possible to fire a rocket from a gun barrel and then have it ignite when it reached apogee.

There are artillery rounds that do this, although they fire earlier since they are only after the increased range.  I don't see why you couldn't extend the principle, with less shell and more rocket.
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Re: Spinlaunch... Can it succeed?
« Reply #65 on: November 26, 2021, 04:21:10 am »
It would be interesting to know if it's possible to fire a rocket from a gun barrel and then have it ignite when it reached apogee.
There are artillery rounds that do this, although they fire earlier since they are only after the increased range.  I don't see why you couldn't extend the principle, with less shell and more rocket.

Yes, I have no doubt it works, it's just a matter of how much advantages you get out of it and at what scale it's possible.
 

Offline thinkfat

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Re: Spinlaunch... Can it succeed?
« Reply #66 on: November 26, 2021, 12:56:45 pm »
The forces on the bearings of this centrifuge will also be quite interesting. Has anyone calculated how carefully one needs to balance the whole thing to keep the vibrations in check?
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Online mfro

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Re: Spinlaunch... Can it succeed?
« Reply #67 on: November 26, 2021, 01:25:19 pm »
The forces on the bearings of this centrifuge will also be quite interesting. Has anyone calculated how carefully one needs to balance the whole thing to keep the vibrations in check?

No. This is basically an academic question as the whole thing isn't going to work anyway.

But given the centripetal acceleration of the setup with the disclosed numbers as around 11000 x g, insert whatever payload mass you find reasonable ( :-DD) into F = m * a and you have the effective forces. 
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Offline thinkfat

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Re: Spinlaunch... Can it succeed?
« Reply #68 on: November 26, 2021, 01:30:06 pm »
I assume a nice fireball, when then projectile vaporizes on exit, hitting air.
A rocket will slowly (in comparison) reach the escape speed - and that's in the least dense medium (downside: it has to carry its fuel).

It will get hot and perhaps require an ablative shield, but will be out of the lower atmosphere in seconds.  Sprint ABM missiles exceeded Mach 10 in the lower-to-mid atmospheric ranges where they operated. I'm sure they got hot.

Yes, they will have to burn something off to get rid of the heat. But there's not just heat, there's also the mechanical effect of slamming a mass into a wall of (comparatively) dense gas and displacing it. That'll be really, really, really loud. The Sprint missile will accelerate to Mach 10 at considerable G, okay, but still not within a split second, right?
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Offline AVGresponding

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Re: Spinlaunch... Can it succeed?
« Reply #69 on: November 26, 2021, 02:13:41 pm »
Since you're such an expert, perhaps you could explain why Thunderfoot is wrong, using the relevant mathematics and physics?
He is not wrong with his calculations, it's just that the publicly available data he used isn't enough for any meaningful analysis. Yes there is high acceleration on the launch vehicle by principle and they appeared to have stability problems on their very first test. Which set of axioms state that one cannot possibly solve those issues? Satellites that survive such high-g launchers are not an entirely new thing and have already been studied.
What else was there? I don't think Saddam Hussein competing on the space launcher market will be a reasonable concern anytime soon. And liquid-propellant engines that can ignite in microgravity are used on satellites all the time.

Just see Thunderfoot vs. Space X. Uniquely the only scam company in the world to successfully operate a manned space program.

...
Regarding rail guns. Rail guns don't work, at least not practically, and even the US military is on the verge of totally giving up on that technology.

Rail gun has a demonstrated velocity of around mach 7 by the US Navy.  Mach 7 is around 2.3km/s and is around Spinlauch's planned launch speed.  So while rail gun may not be suitable to be carried around by ships yet, it is certainly feasible for a fix-located rail gun to get to mach 7 exit velocity.

You have probably missed the news. https://www.thedefensepost.com/2021/07/08/us-navy-railgun/
Basically, huge money sink that never started to work reliably.

I've watched quite a few Thunderfoot videos, and I don't recall him describing SpaceX as a scam company. He has debunked a number of Elon Musk's ludicrous claims, and describes him as a vapourware salesman, rightly so imo.

The scientists and engineers that work at SpaceX are beyond doubt competent and dedicated; the marketing wankers and Musk himself are only dedicated and competent at blowing smoke up people's arses.


I see you admit Thunderfoot's calculations are correct. From what I can see, there is ample data in the public domain to make a meaningful analysis, unless Spinlaunch have also developed some unannounced technology such as frictionless coatings for the launch vehicle, rocket motors that can withstand sustained G forces of 20k+ and remain operational etc.
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Offline thinkfat

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Re: Spinlaunch... Can it succeed?
« Reply #70 on: November 26, 2021, 03:21:19 pm »
The forces on the bearings of this centrifuge will also be quite interesting. Has anyone calculated how carefully one needs to balance the whole thing to keep the vibrations in check?

No. This is basically an academic question as the whole thing isn't going to work anyway.

But given the centripetal acceleration of the setup with the disclosed numbers as around 11000 x g, insert whatever payload mass you find reasonable ( :-DD) into F = m * a and you have the effective forces.

The effective force is of course from the payload, but also from the counterweight. I imagine you could e.g. pump water into the counterweight to finetune the balance automatically while the centrifuge accelerates.
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Online SiliconWizard

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Re: Spinlaunch... Can it succeed?
« Reply #71 on: November 26, 2021, 05:08:21 pm »
We can discuss Spinlaunch to no end, but I'm personally pretty sure it will never go anywhere while having eaten a ton of cash. Where's the popcorn? :popcorn:
 

Offline Rick Law

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Re: Spinlaunch... Can it succeed?
« Reply #72 on: November 28, 2021, 12:40:14 am »
Seems to me the biggest problem is letting go of the payload, not because it will burn up but because of the sudden unbalancing of the spinner. The video Dave posted illustrates the issue pretty well - in most of the windmill destructions I've seen, one arm lets go and the shock of that breaks the other two arms which then let go in sympathy.

But... what if that doesn't matter? When they used to launch rockets I bet no-one ever said "No, this will never work because the first stage won't survive coming down." Losing most of the rocket is just the cost of doing business (or used to be). So what if the destruction of the wheel is just the cost of this style of launching?

Against that, it would be a pretty spectacular loss of functionality...

Releasing the payload is not the biggest problem.  A small one comparing to other problems they must solve.  The bigger problem is actually the centrifugal g force the payload must endure.

At 11000g, as had been said in earlier replies, the payload needs to be pretty much hard like a piece of solid object.  Think about a digital watch.  That little button battery weighting 1gm will have 11kg centrifugal weight!  A 0.1gm IC will exert 1kg weight on the the PCB...  Practically everything not solid may be crushed under it's own centrifugal "weight".   The cost of hardening your product for a 11000g launch will be very high.  So they are left with a very small market of potential customers.

They are launching at Mach 3.  That's not enough to go into space.  It will require further boost by a rocket of some sort.  So the spinning launcher launches a rocket with the real payload inside.  Presumably, you would want to launch that rocket nose first, that means the centrifugal-G would be lateral.  A rocket that could take 11000 lateral-g will be rather hard to do if doable at all.

Well, one could launch the rocket laying flat.  Beside being clumsy to handle, the rocket will come out rotating.  All object launched by this method will come out rotating.  This rotation will not be from the angular momentum of the spinning wheel launder.  It will come from unequal acceleration along the radial direction of the launch wheel different velocity due to different spinning radius.  The out-side end (of the rocket) will be farther from the spinning axis as compared to the inside end -- farther by the length of the rocket.  So the out-side end will shoot out at higher speed than the end that is closer to the spinning launcher axis.  That unequal acceleration velocity results in the rocket rotating end-to-end upon release.  This will add more issues with controlling trajectory.  This launch speed asymmetry actually applies to all loads.  Even if they shoot up just a box, one side will be farther from the spinning axis than the other, so any object will rotate simply because of the chosen method of spinning it to launch.

So on, so on.  The issues are endless.  I can spend days listing them and can still find more after.  Each solvable, I am sure.  Adding the cost of researching and solving all that would be huge amount of money making this a very expensive way to launch anything -- in my opinion.

We can discuss Spinlaunch to no end, but I'm personally pretty sure it will never go anywhere while having eaten a ton of cash. Where's the popcorn? :popcorn:


SiliconWizard is right.  I too am pretty sure that it will not go anywhere.  With that in mind, while SiliconWizard can go for his popcorn, I have a lot of left over turkey to finish...

EDIT:

I use the word acceleration in two places instead of velocity.  While the physics is still technically correct, it is the velocity that matters on release.  The wrong choice of word made the paragraph difficult to understand.  So, I did a strike-out of the old and replace with underlined words.

Unequal acceleration was on also my mind because: there is another unequal acceleration that bends the rocket since the rocket is straight and spinning traces out an arc.  But I decided not to include that.
« Last Edit: November 28, 2021, 12:01:32 pm by Rick Law »
 

Offline CatalinaWOW

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Re: Spinlaunch... Can it succeed?
« Reply #73 on: November 28, 2021, 03:48:07 am »
There are tons of second order problems to solve also.  You can get a glimpse with a much simpler concept.  Large rockets burn huge amounts of fuel in the first few meters of flight.  The Saturn V burned roughly 35,000 kg of fuel in the first 10 meters of motion and is still only going roughly 20 meters/second at that time.  If you just mounted the whole rocket on a hydraulic piston and shoved it the first ten meters you would save all that mass with corresponding improvements in downstream performance.

BUT, to save that fuel you have to light the fires after the piston initiates it's motion.  And in the case of a misfire you have a giant rocket heading into the air and at least partially on fire with an impact zone a few meters from the launch platform.  Space flight is exciting enough without problems like that.

Spin launches are an approach to taking the weight of initial velocity production out of the rocket, but this one seems most efficient at rearranging the location of cash.
 

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Re: Spinlaunch... Can it succeed?
« Reply #74 on: November 28, 2021, 10:47:38 am »
We can discuss Spinlaunch to no end, but I'm personally pretty sure it will never go anywhere while having eaten a ton of cash. Where's the popcorn? :popcorn:

The success or failure of the actual business aside, can we have a straw poll that in 10 years time:
1) Spin launching will be a thing
2) They'll get something small and token into orbit as a test but that'll be it. Too many issues to be practical.
3) They had no chance, the concept is just doomed to impracticaility.

I'm sitting about 2.5
 


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