The Next Generation of Human Spaceflight

[GIThruster]

Laser launchers require propellant in the craft.

http://www.niac.usra.edu/files/library/ ... 97Kare.pdf

[chrismb]

Either way, I'm just saying that I don't believe 'light-pushing' will work in space, whatever the configuration. Makes no sense to me.

[GIThruster]

The physics behind a "light sail" is pretty simple. Photons have mass and even though it's not much, they can impart momentum.

[chrismb]

Show me an experiment that proves this works in space, then.

(Actually photons don't have mass, they have momentum. My claim is that their momentum is gravity-field dependent.)

[Betruger]

What pedantics? If you don't know what you're debating, you screw it up. Where in the OP does GIT specify discussion of "something worthwhile"?

I've got an idea. . .how about Chris and i, and Aero and icarus and Kiteman and anyone else interested, all find something worthwhile to argue over? We're not gonna find much about the Poly to argue, but this country is going to have a new human spaceflight program in a few years and no one knows what it will look like. How about, if we're gonna burn the brain oil, we use it for something useful?

OK, so it is not in this thread.

So I missed that other discussion. My bad.

But, there again, how did GIT address the topic of the thread where he posted that?

If GIT's post was relevant to that topic, then mine is relevant to this one. Or are you one of those 'double standards' kinda people.

I don't see what you mean in either of those two separate statements.

[GIThruster]

Show me an experiment that proves this works in space, then.

(Actually photons don't have mass, they have momentum. My claim is that their momentum is gravity-field dependent.)

Well since all fields extend to infinity, you're not making much of a claim. You're drawing a distinction without a difference, but here's what you asked about:

http://www.jspec.jaxa.jp/e/activity/ikaros.html

[rjaypeters]

Laser launchers require propellant in the craft.

http://www.niac.usra.edu/files/library/ ... 97Kare.pdf

Never said laser launchers didn't require propellant in the craft. But then, so will a TRITON VentureStar.

Please, please, please read and think about the report you sent us. That report is newer than I have seen since I lost hope several years ago...

All of the technologies are being developed for other requirements/customers:

High powered lasers e.g. National Ignition Facility

Lower powered lasers e.g. mostly US DOD projects.

Tracking technologies e.g. again (drat!), mostly US DOD projects.

Launch catapult e.g. USN to replace steam catapults on aircraft carriers.

Etc.

I don't know where you get the trillion dollar estimate. The estimate in the report is $US 2Billion, so be sceptical and multiply by any reasonable factor you please and it's tough to get to $US 1Trillion.

So, we have a reasonable competitor to TRITON VentureStar. Next, I will think about how they can complement each other, because as a true propeller-head, I want them both.

[D Tibbets]

Show me an experiment that proves this works in space, then.

(Actually photons don't have mass, they have momentum. My claim is that their momentum is gravity-field dependent.)

Another link to some information on light pressure. Perhaps the most obvious easily visable effect of light pressure is on the morphology of comet tails.

http://encyclopedia2.thefreedictionary. ... t+Pressure

Dan Tibbets

[GIThruster]

I don't know where you get the trillion dollar estimate. The estimate in the report is $US 2Billion, so be sceptical and multiply by any reasonable factor you please and it's tough to get to $US 1Trillion.

I think you misunderstood the report. 2 things: first is this is not an accounting report. This is a NIAC report. It doesn't do any hard number crunching. They made a guess.

Second thing is the $1 billion figure is not for a laser projector. It's what they guessed would be necessary to develop a 100 MW laser. That's development only, it does not include the cost of building them and as stated previously, you need a lot of them. As something circles the globe it will be continually going out of direct line of sight.

This is an infrastructure rich architecture. It's not the right way to lower launch costs. Remember, fuel is the smallest portion of launch cost. Infrastructure costs much more and the laser solution is going to require much larger infrastructure and a larger standing army of engineers. The cost would be astronomical. Conversely, once you have a TRITON, you have what's needed for both launch and exploration, and you have flexibility you do not have with stationary laser stations that have severe limitations as to the orbits they can contribute to.

[GIThruster]

While we're on the notion of a TRITON Venturestar, I should mention that it's quite possible to solve the two issues X-33 had.

First was that they had a group building the composite tank who did not know what they were doing. They not only had a tank with so many seams that it weighed too much, but it then delaminated. Both these issues could easily be solved in the future. Just hand the issue to Burt Rutan and Scaled Composites.

Second trouble was that the aerospike team found they needed an enormous copper heat sink that added too much weight to the thruster design. That could easily be solved with a fission drive like TRITON. In the case of H2/LOX engines, the propellant supplies the heat that needs to be carried away by the heatsink. In the case of the TRITON, the reactor generates heat that is carried away by the propellant.

Makes a real difference. . .

http://upload.wikimedia.org/wikipedia/c ... W_edit.jpg

[chrismb]

Show me an experiment that proves this works in space, then.

(Actually photons don't have mass, they have momentum. My claim is that their momentum is gravity-field dependent.)

Well since all fields extend to infinity, you're not making much of a claim. You're drawing a distinction without a difference, but here's what you asked about:

http://www.jspec.jaxa.jp/e/activity/ikaros.html

This has no demonstration of 'light acceleration'.

It says "Acceleration and navigation using the solar sail will then be demonstrated (full success level) within half a year. ". Yawn... we wait, and wait.

I have not claimed gravity is a field. If you have read my previous, you will see that I have argued that it is mediated by no fundamental particles, and is not a 'field'.

[chrismb]

Show me an experiment that proves this works in space, then.

(Actually photons don't have mass, they have momentum. My claim is that their momentum is gravity-field dependent.)

Another link to some information on light pressure. Perhaps the most obvious easily visable effect of light pressure is on the morphology of comet tails.

http://encyclopedia2.thefreedictionary. ... t+Pressure

Dan Tibbets

am unconvined the morphology of comet tails is due to solar radiation rather than solar wind. Can you provide contrary evidence to my supposition, as I am not aware of any?

Your link proves nothing, in respect of my statement above.

[GIThruster]

Show me an experiment that proves this works in space, then.

(Actually photons don't have mass, they have momentum. My claim is that their momentum is gravity-field dependent.)

Well since all fields extend to infinity, you're not making much of a claim. You're drawing a distinction without a difference, but here's what you asked about:

http://www.jspec.jaxa.jp/e/activity/ikaros.html

This has no demonstration of 'light acceleration'.

It says "Acceleration and navigation using the solar sail will then be demonstrated (full success level) within half a year. ". Yawn... we wait, and wait.

I have not claimed gravity is a field. If you have read my previous, you will see that I have argued that it is mediated by no fundamental particles, and is not a 'field'.

Well no, I had no idea you were a physicist, Chris. You say you have a theory that says Einstein is wrong? Can you point us at some peer review and tell us in a few words why you think Einstein is wrong? Seems it needs its own thread. Did I miss it somewhere?

[chrismb]

How have I claimed Einstein is wrong?

[GIThruster]

You're not a physicist, are you Chris?

GR is pure field theory.