Space startup wants to sling satellites into orbit with a huge centrifuge

captaincranky

Posts: 18,014   +6,823
Zero dollars. I'm just a mere spectator.
But, but, but, they won't be able to do it without your "help" Dust that wallet off.... :rolleyes: 🤣 🤣 🤣

Proving once again that no "good idea" goes unexploited:

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defaultluser

Posts: 297   +259
Think positive, man! :) And remember that the military has been using electronics in tank and artillery shells for years, subject to 30,000 Gs at firing.
https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.101.9472&rep=rep1&type=pdf
Granted those are shock pulses rather than sustained acceleration, but high-G ruggedization is not something that needs to be started from scratch for this.

I know you are hopeful, but there are better ways than SpinLainch

Space gun has always been a more viable approach (because the instantaneous acceleration can be averaged over the length of that huge barrel), while these things need to endure it during however long it takes to finish swinging (they say about an hour for the final orbital spinner)!

The downside to this: , once they get that big, you're only a State Sponsor away from building a Baby Babylon (and being able to drop orbital bombs nearly anywhere).

https://www.bbc.com/future/article/20160317-the-man-who-tried-to-make-a-supergun-for-saddam-hussein
 
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Avro Arrow

Posts: 1,989   +2,338
TechSpot Elite
Yeah right. In the mean time, would you mind bringing another tanker truck full of RP-1 to the launch pad?

As far as using it powered by electricity, the military has been screwing around with rail guns for over a decade (?). The problem there is, they require so much power to fire, nobody has figured out a way to make it portable enough to carry into battle.

Quite frankly, it's easier and faster to load a 16" shell, than to make some kind of appointment waiting for this contraption to spin up.
Well, sure, but we're not talking about a mobile rail gun application here. We're talking about a stationary launch system for spacecraft. For all we know, it'll have its own dedicated generating station (hopefully hydroelectric but nuclear would work too).
 

wiyosaya

Posts: 6,965   +5,480
You're right about those specific G-forces, but thinking about the physics for a second, you do not necessarily need to get to that level of force.

Achieve orbit requires a certain delta-v - velocity out of the 'canon' in this case. If you increase the diameter of the centrifuge, you can decrease the forces involved while maintaining the velocity required.

F = M(w^2)r

Where F is the force, M is weight, W is the angular velocity, and r is the radius of the centrifuge. If you keep M constant, an increase in the radius will result in a decrease in angular velocity to hit the same amount of force. But we don't care about force - instead, velocity. So re-arrange it like so:

W = sqrt(F/Mr)

So, if you want to maintain the velocity, but reduce the force, then either increase the mass (undesirable in a satellite) or increase the radius of the centrifuge.
The question is just how big does it need to be in order to overcome all the forces acting against it such as atmospheric drag - as @captaincranky and does the required size then make it impractical?

Under the sqrt, it seems to be a directly proportional relationship which, to me, could imply that it may need to be quite big.
 

defaultluser

Posts: 297   +259
The question is just how big does it need to be in order to overcome all the forces acting against it such as atmospheric drag - as @captaincranky and does the required size then make it impractical?

Under the sqrt, it seems to be a directly proportional relationship which, to me, could imply that it may need to be quite big.

Their sales pitch said Football field sized.

I guess the question they have to answer is: is this massive thing easier to build than an extremely long gun barrel (already been working for several years)?

The pitch to improve the pressure wave from the explosive:


The Space Gun has already had a long history that could be harnessed (so why start from the beginning here with Spin?).

 
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mgwerner

Posts: 145   +174
Their sales pitch said Football field sized.

I guess the question they have to answer is: is this massive thing easier to build than an extremely long gun barrel (already been working for several years)?

The pitch to improve the pressure wave from the explosive:


The Space Gun has already had a long history that could be harnessed (so why start from the beginning here with Spin?).

I'll raise that little example with Gerald Bull's Space Gun:
https://nuke.fas.org/guide/iraq/other/supergun.htm

 

captaincranky

Posts: 18,014   +6,823
The question is just how big does it need to be in order to overcome all the forces acting against it such as atmospheric drag - as @captaincranky and does the required size then make it impractical?

Under the sqrt, it seems to be a directly proportional relationship which, to me, could imply that it may need to be quite big.
Here's a Quora page about whether or not the SR-71 needed leading edge deicers.


I really wish whomever's idea this is, would explain how are you going to control heating in an object spinning in air for an hour bringing it up to orbital velocity, without burning it to a cinder.
 

captaincranky

Posts: 18,014   +6,823
I'll raise that little example with Gerald Bull's Space Gun:
https://nuke.fas.org/guide/iraq/other/supergun.htm
Sending objects into space doesn’t always have to be an expensive and complex task conducted exclusively by filthy rich entrepreneurs or governments. Sometimes all you need is a determined Canadian engineer, a backyard, and a Kickstarter campaign — at least that’s what Richard Graf is hoping.

And so, the begging for money begins.
 

sreams

Posts: 225   +341
If the object is already going to be at faster than orbital velocity when it exits the centrifuge, it will need even more heat shielding than a spacecraft would need for re-entry.
 

captaincranky

Posts: 18,014   +6,823
If the object is already going to be at faster than orbital velocity when it exits the centrifuge, it will need even more heat shielding than a spacecraft would need for re-entry.
Well, I'm about as skeptical as skeptical can be about this.

That said, I'm wondering about the time factor of contact with the atmosphere would aggravate or mitigate the heating.

Next, assuming this mess is spun up in a vacuum, the instant the "cork is pulled", it should have an effect similar to a supercharger with the inrush of air.. That in itself would cause a significant deceleration.

As far as the heat goes, I wonder if some ablative covering could be employed to keep the core cool.
 
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BuckarooBonzai

Posts: 39   +21
Anything is possible. In the 1900s people laughed at flying until the Wright Brothers flew in 1903, and just look where we are at today with flying and space flight. Technology takes time to mature and be successful.
 

kiwigraeme

Posts: 729   +534
I'm sceptical as well - is not zero carbon - unless from renewable energy

No ones talked about the device itself - I have visions of shattering CDs.

20% of accerators power is undefined - do they mean spinning at 20% full speed.
or more correctly 20% electricity
Big deal - momentum = 1/2 *m*V^2 - the material stress, the tolerances etc - are they going to magnetic levitation- pressure on ball bearings etc etc .
That prototype looks cheap -what a small concrete pad to anchor it - can't see depth , no safety features visible .

Then there's the electronics - spinning at a speed to get at least sub-orbital - someone here can calculate the timing needed - all we know is 2235 metres/second and 98 000 000 m/s^2- so from that we can calculate the radius .
Anyway lets assume diameter of 50m - so times pi your circumference is roughly 157m =so 14.2 revolutions per sec.

So lets say just need 1 degree accuracy - It's past me bedtime would that be 1 second /(360*14.2)
So your release needs to be real precise . Saying that I think it could be done with a magnetic binding posts , and laser lights on spinner - when light hits say 93 degrees , electricity turned off to binding posts - so could be fine tuned . Still think it will be hard.

Plus release points should be on a mountains 3 or 4k high at least - it's a small projectile - no fuel to be carted in etc .

Plus pumpkin chuckers break the pumpkin it thrown too fast
 

Arbie

Posts: 323   +595
Jules Verne might be pleased. His "From the Earth to the Moon" imagined a big gun doing the same thing. And yeah, nobody was going to survive that either but it was impressive for 1865.
 

sorten

Posts: 103   +145
"its centrifuge uses four times less fuel"

Phrases like this drive me crazy. Which number are we multiplying by 4?

So we're saying it uses 25% of the fuel of traditional rockets?
 

captaincranky

Posts: 18,014   +6,823
@kiwigraeme Kudos on the math. I forget algebra the minute I close the textbook and walk out of the class

What I manged to get out of it, is the fact that if you double the diameter, you half the rotational speed..`That said, you need a diameter of 800 meters, to have the rotational speed be a "realistic" 2 revolutions per second.

Any of that notwithstanding, if you hit.atmospheric pressure at 18,000 Mph, (remember, we're spinning this up in a vacuum),. you might as well be slamming into a brick wall..

If you gradually decrease the vacuum to sea level pressure, the issue of heat rears its ugly head once again. (Keep in mind the windscreen of the SR-71 was made of Pyrex, and it flew above 90% of the earth's atmosphere).

So, what do we do next, super cool the incoming air with liquid nitrogen?
 
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captaincranky

Posts: 18,014   +6,823
Jules Verne might be pleased. His "From the Earth to the Moon" imagined a big gun doing the same thing. And yeah, nobody was going to survive that either but it was impressive for 1865.
If Jules Verne doesn't mind me asking, how was he planning on getting back? :confused:
 

kiwigraeme

Posts: 729   +534
So just a souped up battery powered nerf gun!
Another reason for doubt is - why hasn't the military used this for launching depleted uranium or whatever they use .
Cannonball enters near the centre - accelerates as follows a spiral coil outwards - to go in the direction of the "barrel"
Those Russian Katyusha rocket launchers look cool - but something launching a 10kg metal ball every every second endlessly at say 2000km/h - would pulverise everything in front of it
 

Avro Arrow

Posts: 1,989   +2,338
TechSpot Elite
I was thinking the same thing. Satellite, or whatever, makers will have to engineer their "spacecraft" to withstand this kind of acceleration. Conventional launch vehicles achieve what, 3G at max??
That's a very good point you make. Personally, I think that all of these ideas, while having merit, cannot replace the ultimate idea of a space elevator. Space elevators will ultimately be how we travel to space because they'll be cheap, clean and gentle to use:
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