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Board index » Non-Fiction » Science, Logic, And Morality


Quote of the Week: "History teaches us that men and nations behave wisely once they have exhausted all other alternatives." - Abba Eban, Israeli statesman (1915-2002)

The Starship Enterprise can be built within 20 years

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Stas Bush
PostPosted: 2012-05-15 03:46am 

Glamorous Commie


Joined: 2003-02-26 12:39pm
Posts: 17115
Location: 差不多先生
Destructionator XIII wrote:
Holy shit, 10 kW/kg is better than I imagined to even be reasonable. The one I read (don't have the link anymore; I read it back in 2008 or so) was 1 kW/kg, which I considered spectacular.

If you're reading carefully, these were used just as an example. Their properties (including organic nature) would make it hard to utilize them in space. However, considering even 1kW/kg or 1kW/10kg is enough to start planning realistic solar ship deployments.
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PeZook
PostPosted: 2012-05-15 04:00am 

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Joined: 2002-07-18 06:08pm
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Solar panels have the undeniable advantage of not producing waste heat ; While heat from a nuclear reactor can be used to warm the spacecraft, damage to the cooling system can be totally catastrophic in an environment without ready access to outside sources of cooling water/air: even a reactor that's shut down still produces lots of heat which you will have to radiate away.
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Lord Zentei
PostPosted: 2012-05-15 10:48am 

Space Elf Psyker


Joined: 2004-11-22 03:49am
Posts: 8742
Location: Ulthwé Craftworld, plotting the downfall of the Imperium.
Zinegata wrote:
Lord Zentei wrote:
I haven't yet seen large scale solar electrics that can beat the nukes for heavy loads, though I have admittedly not been following more recent developments. You got links for that?


Have nukes actually progressed beyond the old Project Orion blue prints though? There's been a lot of movement against nukes.

Yes, there has been a lot of negativity lately; though I was thinking more of nuclear-electrics or something along those lines, not nuclear pulse propulsion.
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Sea Skimmer
PostPosted: 2012-05-15 11:34am 

Yankee Capitalist Air Pirate


Joined: 2002-07-03 11:49pm
Posts: 35320
Location: Passchendaele City, HAB
PeZook wrote:
Solar panels have the undeniable advantage of not producing waste heat ; While heat from a nuclear reactor can be used to warm the spacecraft, damage to the cooling system can be totally catastrophic in an environment without ready access to outside sources of cooling water/air: even a reactor that's shut down still produces lots of heat which you will have to radiate away.


Sure, but if you use solar panels you will never be able to explore all the planets, they just don't provide worthwhile power beyond a certain point, IIRC about Uranus distance from the sun. If you had a reactor problem, ejecting the core would work pretty well; then creep home on RTG power.
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Alkaloid
PostPosted: 2012-05-15 01:11pm 

Jedi Knight


Joined: 2011-03-21 07:59am
Posts: 949
Would it be possible to have a nuclear plant and a backup system and if you run into problems with the nuke plant or its cooling system just go with the old Trek standby and eject the damn thing into space? I'm assuming anything manned and exploring planets is going to be modular and assembled in orbit to avoid having to strap the whole thing to one rocket.
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Junghalli
PostPosted: 2012-05-15 08:21pm 

Sith Marauder


Joined: 2004-12-21 11:06pm
Posts: 4999
Location: Berkeley, California (USA)
Sea Skimmer wrote:
Sure, but if you use solar panels you will never be able to explore all the planets, they just don't provide worthwhile power beyond a certain point, IIRC about Uranus distance from the sun.

You could have specialist nuclear spacecraft for missions to the outer system.
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Zinegata
PostPosted: 2012-05-15 09:54pm 

Jedi Council Member


Joined: 2010-06-21 09:04am
Posts: 2259
Hmmm, question regarding Solar powered drives:

In the game High Frontier (which is a very "hard" sci-fi game, complete with Project Orion as a buildable system), solar-powered drives become less and less useful the farther away you get from the sun, to the point that they simply stop working around Saturn / Uranus.

However, you can workaround this to an extent by setting up satellites around Jupiter - which collect solar energy and then beam it using a more focused laser to a waiting spaceship's solar panels.

It still won't get you to Alpha Centauri, but it does make exploration of the Kuiper belt with a solar drive "kinda" possible (albeit still very slow).

Is this scenario realistic in real life or a total pipe dream?
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GrandMasterTerwynn
PostPosted: 2012-05-15 11:24pm 

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Joined: 2002-07-29 06:14pm
Posts: 6513
Location: Somewhere on Earth.
Zinegata wrote:
Hmmm, question regarding Solar powered drives:

In the game High Frontier (which is a very "hard" sci-fi game, complete with Project Orion as a buildable system), solar-powered drives become less and less useful the farther away you get from the sun, to the point that they simply stop working around Saturn / Uranus.

However, you can workaround this to an extent by setting up satellites around Jupiter - which collect solar energy and then beam it using a more focused laser to a waiting spaceship's solar panels.

It still won't get you to Alpha Centauri, but it does make exploration of the Kuiper belt with a solar drive "kinda" possible (albeit still very slow).

Is this scenario realistic in real life or a total pipe dream?

This is absolutely plausible, though if you want to keep the beam usefully narrow, it's going to have to be a very large aperture laser of fairly short wavelength. Though you could to the same with a network of very large mirrors . . . although, if you're at the stage where you can build such installations, you're no longer really "exploring" in the "I plant our flag on this here space-rock for 'MURCA! Fuck yeah!" sense, and more in the "we're going to explore this space rock for volatiles and platinum-group metals to sell on the solar market" sense.
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Zinegata
PostPosted: 2012-05-16 12:17am 

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Joined: 2010-06-21 09:04am
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GrandMasterTerwynn wrote:
This is absolutely plausible, though if you want to keep the beam usefully narrow, it's going to have to be a very large aperture laser of fairly short wavelength. Though you could to the same with a network of very large mirrors . . . although, if you're at the stage where you can build such installations, you're no longer really "exploring" in the "I plant our flag on this here space-rock for 'MURCA! Fuck yeah!" sense, and more in the "we're going to explore this space rock for volatiles and platinum-group metals to sell on the solar market" sense.


Actually, the subject of High Frontier is precisely that - which is to set up outposts / automated factories throughout the Solar System that can produce new materials and technology (in low gravity) which becomes part of a new Solar System-wide economy.

The remote power satellite technology is a fairly late-game technology, which you probably won't get until quite a few asteroids (and likely both the Moon and Mars) are home to some kind of small colony. But in the epic version of the game (with a map extending to the Kuiper belt), it's very possible to setup this kind of wide-ranging satellite network to aid your push to Pluto.

I will note though, that in-game nuclear rockets tend to be superior (the best one in-game being the Salt Water Zubrin; whereas Project Orion is a support system that is very helpful for launching things from planets / moons with higher gravity), but since we tend to play the game for the "experience" of it rather than the "winning" aspect of it my gaming group tends to look at some of the wackier possibilities. Besides which, it's possible for Earth-bound politics to ban the use of all nuclear rockets and powerplants entirely.
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FedRebel
PostPosted: 2012-05-19 09:36pm 

Jedi Knight


Joined: 2004-10-12 12:38am
Posts: 888
Zinegata wrote:
Lord Zentei wrote:
I haven't yet seen large scale solar electrics that can beat the nukes for heavy loads, though I have admittedly not been following more recent developments. You got links for that?


Have nukes actually progressed beyond the old Project Orion blue prints though? There's been a lot of movement against nukes.


Technically Orion could use conventional charges of equivalent yield. Nuclear charges would be more efficient in space, but the touchy issue of the liftoff can be circumvented.
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Simon_Jester
PostPosted: 2012-05-20 04:11am 

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Joined: 2009-05-23 07:29pm
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Conventional charges of equivalent yield would be ruinously heavy; the mass equivalent of a quarter-kiloton bomb is a quarter-kiloton of high explosives. You'd expend the ship's weight in fuel very quickly. To actually make it work you'd need the ship to carry many times its own weight in chemical explosives, just as a normal rocket carries many times its own (dry) weight in fuel- the Saturn V put something like 2000 tons of fuel into about 200 tons of rocket, for instance.

And since an Orion drive has a very high minimum weight (that big pusher plate), almost all the weight you actually got into orbit would be the engine. It'd be very wasteful to do it without nuclear bombs.

The whole point of Orion is to take advantage of the fact that nuclear weapons have just about the highest instantaneous energy-release-to-mass ratio of anything known to man.
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The Duchess of Zeon
PostPosted: 2012-05-23 05:37pm 

Gözde


Joined: 2002-09-18 01:06am
Posts: 14353
Location: Exiled in the Pale of Settlement.
As for cooling a regular nuclear reactor, the (ion particulate) fuel itself does that. Cooling it while accelerating will be trivially easy. Cooling it while it is stopped is what will require an enormous effort.
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Sarevok
PostPosted: 2012-05-23 05:43pm 

The Fearless One


Joined: 2002-12-24 08:29am
Posts: 10681
Location: The Covenants last and final line of defense
Simon_Jester wrote:
Conventional charges of equivalent yield would be ruinously heavy; the mass equivalent of a quarter-kiloton bomb is a quarter-kiloton of high explosives. You'd expend the ship's weight in fuel very quickly. To actually make it work you'd need the ship to carry many times its own weight in chemical explosives, just as a normal rocket carries many times its own (dry) weight in fuel- the Saturn V put something like 2000 tons of fuel into about 200 tons of rocket, for instance.

And since an Orion drive has a very high minimum weight (that big pusher plate), almost all the weight you actually got into orbit would be the engine. It'd be very wasteful to do it without nuclear bombs.

The whole point of Orion is to take advantage of the fact that nuclear weapons have just about the highest instantaneous energy-release-to-mass ratio of anything known to man.


Are not nuclear bombs very expensive to make ? They may have highest energy density of any explosive known to man. But hydrogen or kerosene is cheap compared to what goes into building nuclear bombs.

Or can they be made cheap by mass production (ignoring obvious safety issues) ?
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PeZook
PostPosted: 2012-05-24 03:32am 

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Joined: 2002-07-18 06:08pm
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Location: Poland
Thing is, if you want to use conventional explosives, LOX/H2 fuel has TWO ORDERS OF MAGNITUDE higher energy density than TNT. So using a "conventional orion" type of drive is pointless ; You literally get vastly less ISP out of such an arrangement than a conventional chemical rocket.
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Zinegata
PostPosted: 2012-05-24 04:27am 

Jedi Council Member


Joined: 2010-06-21 09:04am
Posts: 2259
BTW, does anyone know if the Salt Water Zubrin rocket is actually feasible?
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Zinegata
PostPosted: 2012-05-25 12:04am 

Jedi Council Member


Joined: 2010-06-21 09:04am
Posts: 2259
Awwww :(.
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Sea Skimmer
PostPosted: 2012-05-25 08:39am 

Yankee Capitalist Air Pirate


Joined: 2002-07-03 11:49pm
Posts: 35320
Location: Passchendaele City, HAB
Someday new materials might make one possible, certainly impossible today as the engine would most likely destroy itself. Another far out nuclear engine concept would be the fission fragment engine which basically attempts to use nuclear fuel flung through a additional reactor as the propellent itself. IIRC they've had actual proofs of concept of this, though it might never work either in useful terms.
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MrDakka
PostPosted: 2012-05-26 04:37am 

Padawan Learner


Joined: 2011-07-20 07:56am
Posts: 252
Location: CA
Sea Skimmer wrote:
Someday new materials might make one possible, certainly impossible today as the engine would most likely destroy itself. Another far out nuclear engine concept would be the fission fragment engine which basically attempts to use nuclear fuel flung through a additional reactor as the propellent itself. IIRC they've had actual proofs of concept of this, though it might never work either in useful terms.


Isn't that the one with an Isp comparable to antimatter rockets and has an exhaust velocity of around .03c? I know I read a white paper about it; but I can't seem to find the damn thing. :(

The attractive thing about nuclear pulse propulsion is its thrust capabilities which are impressive to say the least; its Isp IIRC is better than any chemical rocket, but not too great compared to other nuclear rockets. Thus it would be ideal for getting stuff into orbit, except for the fact that it rides a pillar of atomic fire to do that.

An interesting tidbit about the charges used for an Orion style spaceship is, that with a little modification, you can create nuclear shaped charges (known as the Casaba howitzer)...
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Sea Skimmer
PostPosted: 2012-05-26 01:17pm 

Yankee Capitalist Air Pirate


Joined: 2002-07-03 11:49pm
Posts: 35320
Location: Passchendaele City, HAB
That would be the one, ISP of 100,000-1,000,000 seconds and in excess of .03c exhaust velocity.
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skinofevil
PostPosted: 2012-06-17 02:42am 

Youngling


Joined: 2012-06-17 12:53am
Posts: 106
Who is the retard who dreamed this crap up, and how is it that he doesn't seem to have even ONE family member able and willing to slap him upside the head for lying about being any kind of engineer?
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