Author Topic: VASIMR Engine  (Read 156154 times)

Online QuantumG

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Re: VASIMR Engine
« Reply #260 on: 04/07/2015 12:13 AM »
While not wishing to get into a debate on this that might take this thread to far off topic it depends if you want to adopt that cynical approach to the future of power generation.

It's not about cynicism. What it comes down to is whether you want to think about sending humans to Mars as "something that happens in the future", which typically means you always think about it that way, or whether you actually want to do it.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline Impaler

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Re: VASIMR Engine
« Reply #261 on: 04/07/2015 12:31 AM »
mainline news article:

VASIMR Rocket Could Send Humans To Mars In Just 39 Days

http://www.huffingtonpost.com/2015/04/06/vasimr-rocket-mars_n_7009118.html?ncid=txtlnkusaolp00000592
Why is it that Zubrin seems to have taken personal umbrage with this technology?

Remember that Zubrin takes umbrage at ALL technology development programs, and all Mars mission concepts that did not launch yesterday.

Offline Robotbeat

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Re: VASIMR Engine
« Reply #262 on: 04/07/2015 12:47 AM »
mainline news article:

VASIMR Rocket Could Send Humans To Mars In Just 39 Days

http://www.huffingtonpost.com/2015/04/06/vasimr-rocket-mars_n_7009118.html?ncid=txtlnkusaolp00000592
Why is it that Zubrin seems to have taken personal umbrage with this technology?

Remember that Zubrin takes umbrage at ALL technology development programs, and all Mars mission concepts that did not launch yesterday.
Which is actually quite odd, then, that he supports nuclear power but not solar electric propulsion, since solar-electric propulsion is FAR more mature (not to mention cheaper).
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online QuantumG

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Re: VASIMR Engine
« Reply #263 on: 04/07/2015 12:52 AM »
Remember that Zubrin takes umbrage at ALL technology development programs, and all Mars mission concepts that did not launch yesterday.

I don't think that's true. I think the objection here is that Bob and Frank both agree that space nuclear reactors are a good idea but that's not what NASA is working on. It's cart before the horse, and in this case they're advertising the cart as being super-fast when pulled by a unicorn.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline Stormbringer

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Re: VASIMR Engine
« Reply #264 on: 04/07/2015 02:37 AM »
erm; why does NASA got to do it? I have seen articles that say two or three big companies are ready to make, not design, make mini reactors that are self contained, no maintenance, safe, small and light and that would only cost a few million apiece. That's fission.

Next LM and well as at least a half a dozen other companies are working on fusion with at least three of those ready to put up or shut up about it.

Why does NASA need to do anything more than buy one of those fission reactors from either  the Japanese or GE and pimp slap the normal government regulatory crap out of the way? Tell the EPA that the whole lot of them can stop emitting Co2 at their earliest convenience. Same thing for the DOE and anyone else that wants to be their usual helpful selves.
When antigravity is outlawed only outlaws will have antigravity.

Offline Tetrakis

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Re: VASIMR Engine
« Reply #265 on: 04/07/2015 03:06 AM »
1. Ready to make? Advertised the possibility of making, yes. Actually deploying in the immediate future, no.

2. Reactors designed for use on earth can't just be launched into orbit. All coolant has to be actively pumped, waste heat has to be expensively removed (there is no river of cold water next to the reactor in space).

Offline Stormbringer

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Re: VASIMR Engine
« Reply #266 on: 04/07/2015 03:17 AM »
these are reactors of advanced design from garbage can sized to small CONEX sized. I think there were two Japanese companies offering them and also GE said they had one. I don't see how a garbage can sized reactor needs a river by it.

This is one of the various mini reactors I have read about in recent years:

http://www.ft.com/cms/s/0/22c1b17a-1f71-11e0-87ca-00144feab49a.html#axzz3WaeylOlG

It uses molten lead and bismuth as a coolant and I'd wager as radiation shielding too. Still... it says the ancilliary equipment takes up an acre. But that is for turbines and the like. What about thermo-electric converters?

and there were others.

http://en.wikipedia.org/wiki/Toshiba_4S

and there are still more.
« Last Edit: 04/07/2015 03:43 AM by Stormbringer »
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Online QuantumG

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Re: VASIMR Engine
« Reply #267 on: 04/07/2015 03:43 AM »
Space reactors and ground reactors are not even slightly related. They don't even use the same fuel.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline Stormbringer

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Re: VASIMR Engine
« Reply #268 on: 04/07/2015 03:44 AM »
At the moment there isn't a such thing as a space reactor so how can you tell? :D
« Last Edit: 04/07/2015 03:45 AM by Stormbringer »
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Online QuantumG

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Re: VASIMR Engine
« Reply #269 on: 04/07/2015 03:45 AM »
Of course there is.. ya know, when you're in a hole, you really should stop digging.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline Jimmy Murdok

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Re: VASIMR Engine
« Reply #270 on: 04/07/2015 03:46 AM »
At the moment there isn't a such thing as a space reactor so how can you tell? :D

There are dozens of Russian reactors and few american ones that were launched to space between the 60's to late 80's.
Same discussion few days ago.
http://forum.nasaspaceflight.com/index.php?topic=36805.120

Offline Stormbringer

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Re: VASIMR Engine
« Reply #271 on: 04/07/2015 03:53 AM »
In that case then there are space rated nuclear reactors...so what were we arguing about again?  ;D
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Offline Jimmy Murdok

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Re: VASIMR Engine
« Reply #272 on: 04/07/2015 05:30 AM »
In that case then there are space rated nuclear reactors...so what were we arguing about again?  ;D
They did exist and russia is making the biggest one in history (1MW & 7T). But if you need 200MW  :o ... well no need to justify.

Offline Stormbringer

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Offline Nilof

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Re: VASIMR Engine
« Reply #274 on: 04/09/2015 11:54 AM »
:)

http://www.sciencedaily.com/releases/2001/01/010103073253.htm

That would require huge amounts of an exotic isomer of americium.

If that was available in the large quantities needed for a reactor, I think you'd be better off doing nuclear pulse propulsion instead. Though the possibility of a nuke in a hand-grenade form factor terrifies me as far as Earth applications are concerned.
« Last Edit: 04/09/2015 11:55 AM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Stormbringer

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Re: VASIMR Engine
« Reply #275 on: 04/09/2015 01:53 PM »
Yeah, that's the draw back with any type of advanced fission tech. At least fusion reactors aren't immediately a weaponization threat. Though anything that can approach relativistic speed or even just orbital speed is by default a terrible potential for misuse.
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Offline nadreck

Re: VASIMR Engine
« Reply #276 on: 04/09/2015 04:49 PM »
Yeah, that's the draw back with any type of advanced fission tech. At least fusion reactors aren't immediately a weaponization threat. Though anything that can approach relativistic speed or even just orbital speed is by default a terrible potential for misuse.

Basically the higher the exhaust velocity, then the better weapon just the engine itself can make. Ion cannons are just ion engines pointed at someone ;-)
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline Hanelyp

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Re: VASIMR Engine
« Reply #277 on: 04/09/2015 05:23 PM »
That would require huge amounts of an exotic isomer of americium.

If that was available in the large quantities needed for a reactor, I think you'd be better off doing nuclear pulse propulsion instead. Though the possibility of a nuke in a hand-grenade form factor terrifies me as far as Earth applications are concerned.
My understanding is that the irreducible minimum quantity of nuclear material for a single bomb is about what you need for a reactor of some designs.  A steady state reactor needs cooling, which increases volume and fuel needed for a critical mass, but can use moderating reflectors which reduce the fuel needed.

Offline Kansan52

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Re: VASIMR Engine
« Reply #278 on: 04/09/2015 06:13 PM »
Solar Thermal. May still have the McDonnell Douglas glossy color handout of their space based, microwave beamed SPS from 1970's (if memory serves).

It was solar concentractor reflecting to a tube running the lenght of the reflector trough. It steamed mercury and ran a steam turbine. Dumped the excess heat, repeat. If the mass could be controlled, a trough along the length of the vehicle might accomplish the job.

3D solar cells. Didn't they test those on ISS (or are)? Basic idea is a layer that reflects the sunlight to the solar cell even at extreme angles.

BASP-Beamer. A big a** solar power station that beams the energy to the vehicle. This assumes the colectors for the beamed energy can be much smaller that solar panel.

Offline Hop_David

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Re: VASIMR Engine
« Reply #279 on: 05/07/2015 05:41 AM »
OK lets keep going with this Hummer/Prius analogy, it is kind of amusing.

You're easily amused.

The flaw in your hill analogy is that EML1 is not the top of a hill, it is more like the lip of the grand canyon with the canyon being the Earths gravity well (it's not literally C3=0 but its very close).  Once your up on the plateau (heliocentric space) it is perfectly flat and the Prius is free to accelerate.  If you were going to use a Hummer to push a Prius you would do it going up the side of the canyon UNTIL you got to the lip, not after that point.
 

It's a flat plateau after you reach C3=0? Um, no. Your Grand Canyon metaphor is way off base. Once you reach reach the edge of earth's Hill Sphere you still need another 3 km/s to raise your aphelion to 1.52 A.U.



Your correct that we can just depart from EML1 directly to Earth Escape without doing any swing buys of the moon or Earth.  And the DeltaV is VIRTUALLY THE SAME.  The Chemical high thrust system gets a LITTLE boost of something like 100 m/s from plunging deep into thouse gravity wells and burning with an Oberth effect.


Wrong.

Falling from a high apogee you'd be moving 10.8 km/s at perigee.

At that speed, a .5 km/s burn will give you 3 km/s Vinfinity.

 

.4 km/s to drop from EML2 and a .5 km/s perigee burn for TMI. The delta V from EML2 to TMI is only .9 km/s. So the booster stage can be a lot smaller than the MTV. Accordingly I ditched your Hummer for the more appropriate Moped.

After separation it will take the Moped another .9 km/s to get back to EML2 but this will take a lot less propellent since the Moped has much less dry mass. With an .18 km/s delta V budget and no need to endure an 8 km/s atmospheric re-entry, the Moped's reuse becomes a little more plausible.

In the mean time the MTV is on its way to mars without the mass of the moped.

If a one km/s acceleration takes 11 days, that LITTLE boost saves 33 days.

Of course mining and infrastructure capable of making hydrogen/oxygen bipropellent would also be able to make water that can be used for drinking, sanitation and radiation shielding. Also oxygen to breathe. If half of the MTV's mass is loaded at EML2, that halves the GLOW from earth's surface.

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