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

DonPedro

Member
Mar 28, 2013
688
1
Oslo, Norway
http://www.popsci.com/technology/article/2010-11/nasa-engineers-propose-combining-rail-gun-and-scramjet-fire-spacecraft-orbit

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

1. Beef up local generation capacity so that there is spare 180 MW whenever they want to launch
2. Use high performance batteries (e.g. 581 Model S 310kW batteries)

I imagine No. 1 would be easy if connect to e.g. the New York powergrid and willing to delay flights to launch them during off-peak hours. However, I also imagine that a rocket launching site will be built somewhere far more rural than that, and that new generation capacity would have to be built.

So probably No. 2 is the way to go? :)
 

jhm

Well-Known Member
May 23, 2014
9,319
30,991
Atlanta, GA
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.
 

Cosmacelf

Well-Known Member
Mar 6, 2013
8,425
20,111
San Diego
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.
 

bxr140

Active Member
Nov 18, 2014
2,694
3,602
Bay Area
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...
 

AWDtsla

Active Member
Mar 3, 2013
4,262
3,952
NE
Looks like a super capacitor app to me. The discharge rate would have to be very high, too high for LiIon.

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?

- - - Updated - - -

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

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

- - - Updated - - -

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

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

WarpedOne

Supreme Premier
Aug 17, 2006
4,341
6,360
Slovenia, Europe
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.
 

markwj

Moderator, Asia Pacific
Apr 10, 2011
4,600
1,211
Hong Kong
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.
 

LuigiV

Member
Jan 17, 2014
49
0
Perth, Australia
- it is reusable by definition, not only by design

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.
 

scaesare

Well-Known Member
Mar 14, 2013
8,253
13,206
NoVA
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.
 

Reykjavik

Member
Dec 9, 2013
201
1
New York
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.

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.
 

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