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Catapult to Orbit - SpinLaunch


Shpaget
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An obscure (at least for me) company apparently scored a "a responsive launch prototype contract " with US DOD.

https://www.businesswire.com/news/home/20190619005661/en/SpinLaunch-Secures-Contract-Revolutionary-New-Space-Launch

http://www.spinlaunch.com/SpinLaunch_Media_Fact_Sheet.pdf

They speak of kinetic hypersonic launch system with final circularisation done by a small rocket, five launches per day at $250k a pop:

Quote

After ascending above the atmosphere, a relatively small, low-cost onboard rocket will be used to provide the final required velocity for orbital insertion. Because the majority of the energy required to reach orbit is sourced from ground-based electricity, as opposed to complex onboard rocket propulsion, total launch cost is reduced by an order of magnitude over existing launch systems. Due to its unique technology, SpinLaunch is able to offer readily-available, low cost, dedicated launches at high frequencies. SpinLaunch is working to provide up to five launches per day at a price of $250,000 / launch.

They don't actually say what is their proposed system, but they say what it is not:

Quote

Since the beginning of the space program, ground-based non-rocket launch systems, such as rail guns and ram accelerators have been proposed to achieve this goal, however all have employed unproven technologies with cost-prohibitive initial capital investment. This is how SpinLaunch is different.

They don't list any specification for mass to LEO or any other relevant number, so it's hard to say anything, but they expect first launch in 2022.

Sounds fishy.

Every time I hear about kinetic launch to orbit I remember the Pascal-B and how the manhole cover probably didn't actually reach space.

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Very fishy, forces involved will be extremely high, atmosphere will also be an major problem. 

Now something like this might be plausible on the moon in the future if we mine it. No air resistance and low gravity makes it interesting. 

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I think its an interesting idea. It sort of reminds me of the time when flight was first invented and people experimented with a wild variety of different designs. I am skeptical of this however, the payload may not survive launch at all due to heavy g-forces and atmospheric heating. If i were to start a smallsat launching company, i would rather improve an already existing and tested idea, rather than coming up with a new and untested gizmo. 

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51 minutes ago, Nightside said:

I tend to think that people who want catapult launches don’t really understand orbital velocity.

That's not what they are doing, though.

d81fc4bfc6047c6382bedab3724828e0-730x430

The basic idea is to accelerate the rocket to ~1 km/s while on the ground. Stage sep of Falcon 9 is around 2 km/s. The goal is to provide half of that stage one energy before leaving the ground, reducing the size of the remaining stages.

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2 minutes ago, tater said:

The basic idea is to accelerate the rocket to ~1 km/s while on the ground. Stage sep of Falcon 9 is around 2 km/s. The goal is to provide half of that stage one energy before leaving the ground, reducing the size of the remaining stages.

During the Starlink launch, 1 km/s was reached at around 30 km altitude. They would need to increase acceleration dramatically to reach that 1 km/s in reasonable distance, reducing the variety of payloads due to the inability to survive the initial G forces.

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1km/s sounds feasible, but I think the big hurdle might be economic. If you're a cubesat manufacturer (I'm assuming this will launch cubesats) you are probably have a small budget, so designing a satellite to survive high G-forces might be too prohibitive. I'll remain pretty skeptical until they produce results, but good luck to them.

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19 minutes ago, Shpaget said:

During the Starlink launch, 1 km/s was reached at around 30 km altitude. They would need to increase acceleration dramatically to reach that 1 km/s in reasonable distance, reducing the variety of payloads due to the inability to survive the initial G forces.

yeah, only works for robust, and likely small, payloads.

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28 minutes ago, tater said:

That's not what they are doing, though.

Doh, that s what I get for not reading the whole page, I read as far as “launch payload without a rocket” I guess they meant without a huge 1st stage...

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A 25m radius arm at 400 rpm is 1047 m/s tangential velocity. That's over 4400g, however. Up the radius to 100m, and drop the rpm to 100, and you get the same velocity, but 1/4 the g load (still over 1100g!).

 

Apparently missile components routinely get hardened to 1200+g, and there are "smart" artillery rounds that have electronics that deal with 10X that...

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Now put a payload on that 100 m arm. If the payload + upper stage rocket is very conservative 1000 kg, you're stressing the arm with about 1000 tons. The arm itself needs to be massive.

Edit:

Of course, once you release the payload, you suddenly have a 1000 ton imbalance on your spinning contraption.

Edited by Shpaget
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16 minutes ago, Shpaget said:

Now put a payload on that 100 m arm. If the payload + upper stage rocket is very conservative 1000 kg, you're stressing the arm with about 1000 tons. The arm itself needs to be massive.

Edit:

Of course, once you release the payload, you suddenly have a 1000 ton imbalance on your spinning contraption.

Yeah, it seems like a non-trivial problem.

The tech would be super useful on "not Earth," though. The Moon, for example...

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3 hours ago, tater said:

That's not what they are doing, though.

[image deleted]

The basic idea is to accelerate the rocket to ~1 km/s while on the ground. Stage sep of Falcon 9 is around 2 km/s. The goal is to provide half of that stage one energy before leaving the ground, reducing the size of the remaining stages.

~1km/s is roughly mach 3, which by my ancient rule of thumb implies that you could reduce the mass of the rocket in half.  This gives you a similar problem to the Stratolauncher, where there is no feasible means to scale up your rocket to respond to what payloads need to be launched.

On the other hand, that type of velocity through the atmosphere might be ideal for a ramjet/scramjet first stage to get another 1km/s or so and lop another 50% (75% total) off the rocket.  Don't forget that Falcon 9 second stage is nearly all fuel, while the first stage requires 10 times as much thrust, and I'd expect that it would also be more hydrogen-friendly (and only need one type of fuel).

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7 hours ago, Shpaget said:

How does that mesh with "new $7 million test facility on 10 acres at New Mexico’s Spaceport America" they started building? Are there any suitable mountains over there?

The spaceport is on the flats, though there are substantial mountains nearby.

https://www.google.com/maps/place/Spaceport+America/@32.9848975,-107.0325427,29643m/data=!3m1!1e3!4m5!3m4!1s0x0:0x19c787f1198f25cf!8m2!3d32.9903796!4d-106.975041

10 acres is tiny, however.

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48 minutes ago, Ultimate Steve said:

The thing is, the 1km/s bomus in weight reduction is probably offset by the fact that you now have to beef up your rocket to handle the gee loads

Yeah, this idea seems bizarre for Earth. I could see it on the Moon, though.

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23 minutes ago, tater said:

Yeah, this idea seems bizarre for Earth. I could see it on the Moon, though.

Or even lighter worlds. However, the lighter the world, the less we would have a need to be there long enough to launch stuff into orbit around it. Like on Phobos, for example, you could probably literally throw a small satellite into orbit, but when are you going to need to do that?

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24 minutes ago, Ultimate Steve said:

Or even lighter worlds. However, the lighter the world, the less we would have a need to be there long enough to launch stuff into orbit around it. Like on Phobos, for example, you could probably literally throw a small satellite into orbit, but when are you going to need to do that?

You can throw useful stuff off the surface. On the Moon, ice, for example.

ISRU on the surface that uses propellant to get to space wastes propellant if you can use electricity, instead.

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This 2018 article includes the following passage:

Quote

SpinLaunch plans to use a centrifuge spinning at an incredible rate. All that momentum is then harnessed to catapult a payload into space at speeds one source said could be around 3000 miles per hour.

 

He says “SpinLaunch employs a rotational acceleration method, harnessing angular momentum to gradually accelerate the vehicle to hypersonic speeds. This approach employs a dramatically lower cost architecture with much lower power.”

So it's not a linear catapult (it would hardly be 'SpinLaunch', now would it), and 10 acres is probably enough for a tech demonstrator.  IIRC space-grade electronics are rated for about 50g (at least for shock, idk about sustained), so it's actually your structure that's going to have to be beefed up - usually those are rated for less than 10g including safety margins.

This seems pretty fishy to me. The tensile forces on the launch arm are going to be pretty massive unless the radius is large.  That might be the gimmick though - use a material with either a) great tensile strength (CNTs) and/or b) great specific strength (CNTs) and use that to make a really long arm. I think specific strength here is actually more important because the taper on the arm would be less severe, and the longer the arm the lower the total stress at the end of it is. There's some optimization to be done there but I don't really want to get into it. 

Either way, I don't see payloads being rated for more than a few hundred gee - your structural mass is going to increase significantly unless your payload is pretty small (especially because it will have to sustain large forces in two axes - longitudinal during spin and axial during flight), and flight computers and sensing systems aren't going to be able to be hardened significantly without increasing mass/volume to be point where one of those becomes constrictive.  These payloads are basically going to be bricks.

What really gets me though, is the picture posted above. If it is anything representative of the final vehicle, I'll eat my hat. Using the door and flight of stairs on the right, I would estimate the vehicle to be between 20 and 30 m long. Even with a 1 kps head-start (and drag aside), you're not going to get much more than a hundred kilos to orbit - and probably not even that much.  Plus, the pointy nosecone significantly constrains the geometry of the payload.  This system is going to be pretty niche, and it might struggle to attract customers due to the mass/volume/hardening constraints.

As was mentioned, this would be a great candidate for a scramjet accelerator. I've been trying to think of some more sinister military applications where this would be tactically niche, but I can't come up with anything.

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