Nuclear rockets are very very very bad idea?

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Polishguy

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MeteorWayne":2lgqomxv said:
It doesn't work like that. By the the time the "object" get to GEO, you will have completed several day and night cycles, during most of which the sat would not be visible in the sky.
I'm not doubting what you say, I'm just trying to make sure I understand. If the object's lateral velocity is equal to the velocity of the laser on the earth's surface, wouldn't it be visible in the sky constantly? Because the laser and the object are moving at the same velocity, only the object is also moving up.
 
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neutrino78x

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I believe the laser would just get the object to the edge of the atmosphere, at which point onboard rockets would take over (or it would dock with one of those rotating tethers or something). It is basically the same idea as using an airplane to get the rocket to the edge of the atmosphere, or using a balloon...all these techniques are intended to get the rocket to space, at which point the rocket takes over. So you would probably start using the rocket at like 30 km altitude, the maximum altitude for commercial flight according to this page?

--Brian
 
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neutrino78x

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Polishguy":2k5ltwjz said:
Ah, this is an interesting article. But lightcraft do have their own problems. It is much easier to sabotage a launch by a lightcraft than a chemical launch. If one were to sabotage the Space Shuttle in flight, for example, you'd need to launch an ASAT missile. For a lightcraft, one must only set off a smoke grenade near the laser.
I don't think that would disrupt it long enough. The laser is pulsed. You have to block the laser in a sustained way. Plus, I assume the crew would be able to eject in such a situation.

And 1/1000 of all humanity's annual power usage may not seem like a lot...until you calculate what it really means.
Well it means 1/1000 of humanity's annual power usage. You had claimed that more energy than humanity generates in a year would be needed, so I was just proving that statement to be incorrect.

Now, what we don't know is, does it need that power, total for the entire flight, or does it need that each second?

It's actually a lot; Hoover Dam produces just 2 gigawatts at maximum capacity. However, higher amounts of energy have been compressed into lasers before.
I assume you would generate the power over time, and store it somehow.

As for making launches accessible for all nations, is this really desirable? Do you want to give Iran or North Korea the ability to place kinetic weapons into LEO?
In theory, any nation has that capability, if they are not under sanctions.

Anyway, the lightcraft has made me curious, and I'm e-mailing the physicist in charge (Dr. Leik Myrabo) to ask about whether it has the potential to replace chemical rockets for launch to earth orbit.
He has a company that intends to launch satellites with it. Note that the laser is just bringing the satellite up to a certain point, then rockets would kick in.

--Brian
 
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neutrino78x

Guest
Also, the other thing I forgot to say, this laser effect, as least, the one they are using to push objects up, requires an atmosphere, so yeah, it definitely is intended to just get the thing to the edge of the atmosphere.

The principle is that the laser is reflected by the bottom of the target, heating the air underneath to a plasma, propelling the object.

--Brian
 
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orionrider

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The craft needs a tank of reaction mass, be it gas, liquid of ablative, to be laser-propelled in the vacuum. In fact, that's how they intend to use laser to de-orbit space junk, by vaporizing a part of it :idea:
This launch method only works if you have airborne or orbiting lasers to provide the necessary tangential velocity. It means at least 2 or 3 lasers to get from the ground to orbit. Put another string of lasers on the Moon and you can give the initial velocity to an interplanetary craft, sparing a lot of mass on the craft itself. But the laser stations would have to be huge!

Sounds like Nuclear is going to be cheaper after all, at least medium term ;)
 
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Valcan

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orionrider":3c78kivv said:
The craft needs a tank of reaction mass, be it gas, liquid of ablative, to be laser-propelled in the vacuum. In fact, that's how they intend to use laser to de-orbit space junk, by vaporizing a part of it :idea:
This launch method only works if you have airborne or orbiting lasers to provide the necessary tangential velocity. It means at least 2 or 3 lasers to get from the ground to orbit. Put another string of lasers on the Moon and you can give the initial velocity to an interplanetary craft, sparing a lot of mass on the craft itself. But the laser stations would have to be huge!

Sounds like Nuclear is going to be cheaper after all, at least medium term ;)
It always was it just had the Nuke word in it and some people including politicans get stupid when its used.
 
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nec208

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The problem why we do not have 8 or 10 countries in the world or more putting people in space is not of smarts but cost.Even the 3 countries in the world are under major lobby for the government to go with space probes and not putting people in space.Really in the 60's it was pride a country can put people in space and going in space was big fad and every kid was into rockets .Now it is dumbing down science and intellectual.Look at the schools and look at TV tank overhaul ,monster truck ,ice road truckers ,ice pilots ,forensic ,murder and crime , fixing up cars, so on.

People are obsessive with crime,,forensic,war and militay and reality TV and that is what takes up most of the learning channels on TV now.It hard to get science and intellectual stuff on TV.

Again 8 or 10 countries in the world or MORE could put people in space if they really wanted to give the money.Countries want to put money in space probes not put money to put people in space,


Look at Canada do you really think Canada is going to spend millions of dollars to make a space shuttle to put people in space and spend millions of dollars to keep it going every year when the militarty is so out of date from the 70,s and long wait times in the ER.And the UK has even longer wait times in the ER.


It money money money meony.They cannot even inprove the long wait times in the ER or give money in social programs for the needy and they are going to cough up money to put people into space.

To they get off Chemical rockets on to some better system or make Chemical rockets better the 3 countries are going to be the only countries that can put people in space and with major lobby for the government to go with space probes and not putting people in space.Not to say launching rockets take along time of getting the rocket and launch site ready.And no where do we have weekly launches or 3 or 4 launch every month.
 
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nec208

Guest
neutrino78x":csufeiy9 said:
I believe the laser would just get the object to the edge of the atmosphere, at which point onboard rockets would take over (or it would dock with one of those rotating tethers or something). It is basically the same idea as using an airplane to get the rocket to the edge of the atmosphere, or using a balloon...all these techniques are intended to get the rocket to space, at which point the rocket takes over. So you would probably start using the rocket at like 30 km altitude, the maximum altitude for commercial flight according to this page?-Brian

What are the problems with laser ? I thought laser was very very small.So could not take up 4 or 8 people in space.May be 3 tops.But laser was very cheap than Chemical rockets .

Some people say nuclear rockets are more costly than Chemical rockets so really will not help with bringing cost down.
 
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Polishguy

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nec208":hvucem2z said:
What are the problems with laser ? I thought laser was very very small.So could not take up 4 or 8 people in space.May be 3 tops.But laser was very cheap than Chemical rockets .

Some people say nuclear rockets are more costly than Chemical rockets so really will not help with bringing cost down.
Meteor Wayne and I just had a discussion on the problems with laser, specifically that it's useless for LEO. And I'd like to point out that the gigawatts required are hard to come by, since we actually have very little infrastructure in place for storing electricity.
And chemical can be quite cheap. Estimates in the '60s for a chemical design thought they could bring it down to $60 per kilogram (google "Astronautix Sea Dragon". You'll get a good page for it).
 
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nec208

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Meteor Wayne and I just had a discussion on the problems with laser, specifically that it's useless for LEO. And I'd like to point out that the gigawatts required are hard to come by, since we actually have very little infrastructure in place for storing electricity.
Has of now laser will not work do to the crude laser power problem and distortion of the laser in the atmosphere .

And anti-matter is way to costly to the extreme and cannot be contained or controlled.So there is no point talking about anti-matter or laser for other 70 or 100 years to the problems are fixed.Well nuclear rockets are way more cheaper and can take up more payload.

I think has of now nuclear rockets or Chemical rockets are the only option.May be in 100 years the space elevator ,anti-matter ,laser or mono magnetic propulsion if one can make monopoles in the lab.If not than all you going to have is nuclear rockets or Chemical rockets .
Well nuclear rockets could take up 2 or 3 times the payload than Chemical rockets that is alot cheaper.But I think in the future the space elevator or anti-matter will fix all these problems.
 
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robertfortner

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pathfinder_01 wrote:
The trouble with nuclear thermal is that no material can stand the heat needed so the reactor is operated in a controled meltdown.
The NASA reports online I've found talk about corrosion and show it as less and less of a problem over generations of engines. Is there a citation for the fundamentally unsolved-ness of the problem? Does it remain significant even with advances in reactor design and new materials?
 
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neilsox

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There is hafnium nitride, melting point 3310 c = almost 6000 degrees f, but hafnium is expensive, because the ore is rare.
Nuclear rockets operating in space, far from Earth can, perhaps be unshielded, with no containment structure and other safety stuff / thus light weight. Neil
 
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MeteorWayne

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Both of these have nothing to do with the subject of this discussion. (and you posted the same link twice :( )
 
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