This must be an application for Tesla batteries: Launching NASA spacecraft

Yes, this could be a great application for Tesla batteries, and I would think Musk would be pretty keen on it.

The Model S 85 kWh delivers 310 kW. So about 50 MWh battery should be able to deliver 180 kW. So Tesla could provide such a battery for $10 - $20 million. Given that the whole project could cost around $1 billion and save millions of dolars in rocket propellant per launch, $20 million for the battery is pretty affordable. Moreover, when the 180 MW battery is not being used for launches, it could serve as peak power provider to the grid.

Looks like a super capacitor app to me. The discharge rate would have to be very high, too high for LiIon.

Brilliant. NASA just figured out how to solve the wrong problem. I knew government scientists were good for something.

The real problem is reusing the expensive first rocket stage. Propellant is a small fraction of total launch costs. The figure I've heard is $500K of a $60M rocket launch. It would make much more sense to figure out how to reuse that $30M first stage than saving $250K in fuel. Which is what SpaceX is doing.

I dunno...F9 first stage separates at 50 miles-ish. 200k feet is 38 miles.

Reusability isn't necessarily the only answer to cheap LVs, but spacex looks like they'll make the concept work. Its sexier than the Russian method, anyway...

Robert.Boston said:

Looks like a super capacitor app to me. The discharge rate would have to be very high, too high for LiIon.

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Uhm, no you only need about ~450 85kWh packs to output that. Why does everybody always rush to the new technology that will magically fix a problem that doesn't exist?

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Cosmacelf said:

Brilliant. NASA just figured out how to solve the wrong problem. I knew government scientists were good for something.

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You mean the same people that created the space truck to nowhere?

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DonPedro said:

As I see it, NASA will have two basic options for the electricity requirements here:

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MCT will be flying to mars before this gets its first shovel of dirt.

I don't understand the negativity. Because Musk is not (yet!) doing it, it is bad?
If Musk did it, everybody would dance on his geniousness!

Using a railgun is exactly the same thing as reusable first stage. Actually it is even better, because:
- it does not go up, so it cannot crash down
- it can be heavy as it needs to be
- it can use other energy production methots, not only burning dinos big time
- it is reusable by definition, not only by design
- it means electrifying rockets i.e. hybrid rockets

The only real downside to it is that it is not easily transportable i.e. it is stationary. And it should be build somewhere in highlands, as high as terrain allows.

It needs to accelerate ~200tonne projectile up to ~supersonic speeds... Building around of 10 GJ of kinetic energy.
Hydrogen peroxide has up to 813 Wh/kg or about 3MJ/kg max. At ~50% efficiencty, only accelerating up to 1 mach would burn 10 tonnes of rocket fuel.

I also don't get the negativity.

The proposal seems to address both the first stage reusability as well as propellant cost issues.

Whether it is practical or not I guess depends on a lot more factors than the 180 megawatts required for launch.

WarpedOne said:

- it is reusable by definition, not only by design

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I wouldn't be so sure of that. Material science needs to make a few breakthroughs first before that can be true. Right now, no existing rail gun can be fired more than a few times before the rails destroy themselves and need to be replaced. That's the big why rail guns are still haven't left the lab yet, despite decades of R&D.

A few things that think they are misusing the term "railgun"[1] here:

1) They state: "A 240,000-horsepower linear motor ..." is what propels the craft.

2) The compare it to the Navy's planned new electromagnetic carrier catapults, which as far as I know are also linear motor based, not railguns

3) They state: "The craft accelerates from 0 to 1,100 mph (Mach 1.5) in under 60 seconds— fast, but at less than 3 Gs, safe for manned flight.", which would seem too slow to be a true railgun.

Bad reporting, I'd bet.

[1] Which actually uses Lorentz forces from current applied across the projectile itself.

Cosmacelf said:

Brilliant. NASA just figured out how to solve the wrong problem. I knew government scientists were good for something.

The real problem is reusing the expensive first rocket stage. Propellant is a small fraction of total launch costs. The figure I've heard is $500K of a $60M rocket launch. It would make much more sense to figure out how to reuse that $30M first stage than saving $250K in fuel. Which is what SpaceX is doing.

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Reducing the fuel requirement doesn't just save on fuel costs, it also means you can use smaller fuel tanks and a smaller engine, and it makes re-usability much more realistic. The plan according to the article is to actually use a jet powered aircraft that is launched by the rail gun system, which would be re-usable.

There is a lot to be gained by doing it that way, and if we can get all the pieces to work right, it might be better than a vertical rocket that is re-usable.

This problem is well on its way to being solved without batteries (too heavy). Due to NDA I can't share unfortunately.

jkeyser14 said:

This problem is well on its way to being solved without batteries (too heavy). Due to NDA I can't share unfortunately.

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Why should weight matter? The power source is firmly anchored on the ground.

Robert.Boston said:

Why should weight matter? The power source is firmly anchored on the ground.

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My fault, I took the battery reference to mean the on-board power and not the launch power.