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Space, the final frontier... - Page 2

post #41 of 49
7/16/11 at 6:06pm
Quote:
Originally Posted by Splinemodel View Post

... A fusion reaction creates a _force_...

No, a fusion reaction releases energy. That energy still needs a reaction mass to turn the energy into force.

Perhaps you know that, and we're just not making our thoughts clearly understood at these keyboards.
From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, "Look at that!" -...
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From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, "Look at that!" -...
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post #42 of 49
7/16/11 at 6:13pm
Quote:
Originally Posted by Splinemodel View Post

The idea of a fusion rocket is old enough, and thoroughly conceptualized, that it has manifested into basically all sci-fi. The only thing that is missing is the steady-state fusion.

Yes, and those fictional fusion rockets still required a fuel tank... A fusion motor will be many orders of magnitude more efficient than our chemical rockets, but still require a "fuel tank" of reaction mass... Which could be something as simple as water ... Or whatever other mass is readily available. (We're going to be using these things in a vacuum, we won't have an atmosphere of freely available reaction mass to negate the need for a "fuel tank".)
From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, "Look at that!" -...
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From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, "Look at that!" -...
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post #43 of 49
7/16/11 at 6:37pm
Quote:
Originally Posted by Splinemodel View Post

You are mistaken. Thrust is provided by force being applied in equal and opposite directions. A fusion reaction creates a _force_. Expansion of gas in a chemical reaction is also a _force_, and the exhaust is really just a byproduct of the gas expansion. This is basic newtonian physics. Before you try to lodge further arguments on the matter, you should do some research & homework.

The idea of a fusion rocket is old enough, and thoroughly conceptualized, that it has manifested into basically all sci-fi. The only thing that is missing is the steady-state fusion.

I fail to see how what you say negates anything that I said. If you want to get off Earth, you'll need to get to at least 25k mph. If you are doing it through a rocket technology where you are throwing stuff out the back, you're are going to need a lot of what you are throwing out the back. If you can get 10x the ISP of a typical rocket and maintain thrust with a "fusion rocket" it'll be a big win. But color me skeptical. Pulse detonation of a nuclear bomb could maybe work, but I'm doubtful.

For in-space, a fission reactor with an ion drive sounds good to me.
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post #44 of 49
7/16/11 at 7:40pm
The helium and oxygen (if heavy water is used) byproducts are sufficient to drive a vehicle. The use of a fusion reactor as a heat engine for secondary fuel gas expansion is therefore NOT the design objective.
Cat: the other white meat
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Cat: the other white meat
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post #45 of 49
7/17/11 at 3:34am
I agree propulsion is key in solving a lot of issues getting off the ground, accelerating to a planet and especially decelerating as well to enter orbit/land.

Otherwise we really are too constrained by issues of mass, time to destination and the ability to cover massive distances. Let alone powering habitats during travel and on the moon and Mars.

I'm not convinced about fission for space travel, we seem to be having trouble with that here on earth... Convince me otherwise. Fusion? Hopefully harnessed properly within the next 50 years. Or maybe we'll discover how to use antimatter or something else coming from particle physics research.
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post #46 of 49
7/18/11 at 8:43am
Quote:
Originally Posted by Splinemodel View Post

The helium and oxygen (if heavy water is used) byproducts are sufficient to drive a vehicle. The use of a fusion reactor as a heat engine for secondary fuel gas expansion is therefore NOT the design objective.

You still need direct the helium (and oxygen) out the back. If you could direct the neutrons, those too. But you are still bound by the momentum transfer of the particles. And you'll need a lot of hydrogen to feed the reactor as you'll need a lot of byproduct to generate significant thrust. That'll mean some big propellent tanks.
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post #47 of 49
7/18/11 at 8:47am
Quote:
Originally Posted by nvidia2008 View Post

I'm not convinced about fission for space travel, we seem to be having trouble with that here on earth... Convince me otherwise. Fusion? Hopefully harnessed properly within the next 50 years. Or maybe we'll discover how to use antimatter or something else coming from particle physics research.

The fact that we can design, build and operate fission reactors while we have never achieved a net gain in a fusion reactor appears to be convincing enough to me.
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post #48 of 49
7/24/11 at 12:33pm
Quote:
Originally Posted by Bergermeister View Post

In short, it would be a one-way adventure.

Sign me up.

There have always been a few willing to push the boundaries to further humanity. We are going to require the same at some point - or we, as a species, die on this rock...
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post #49 of 49
7/24/11 at 12:53pm
Quote:
Originally Posted by Shrike View Post

Like Final Cut Pro 7, the architecture was on its last legs. To continue with it would have handicapped the future. Of course, the current management isn't inspiring any confidence in winning the future, but to do anything beyond shuttle, the program has to be retired one way or the other.

Exactly. And while no fan of either the Democrats or Republicans, this isn't Obama's fault. The shuttle program went on too long as it is.

We should have never lost the ability to build the Saturn V...
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