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jaredGalen
Interesting article, the 1-week to mars claim seems dramatic. It would be interesting to see some the basis for this though.

http://science.slashdot.org/science/07/09/13/2328233.shtml
Eric Hartwell
It's the magic of constant acceleration. Using the Space Math calculator at http://www.cthreepo.com/cp_html/math1.htm, if we assume a constant acceleration of 1G for the first half of the trip and constant deceleration of 1G for the second half, it would take about 1.7 days at closest approach (55.75 million km) or 2.85 days at 1AU. Mars hardly moves relative to the Earth in only a few days, so with this kind of speed you can follow a straight line path instead of worrying about messy orbits.

With constant 1G acceleration/deceleration you can visit Jupiter in less than 6 days, Saturn in less than 10, and even Pluto in less than 3 weeks. The 4.22 light year trip to Proxima Centauri would take only 4.8 years (3.5 years to the people onboard, due to time dilation).

Of course, there is a minor tradeoff due to Newton's second law: it takes energy to generate that constant acceleration. In the real world, the Dawn spacecraft's ion drive will produce an acceration a million times less than 1G, and it takes years to get anywhere nearby.

We're still waiting for antimatter drives, negative-mass generator, or the ever-handy space warp.
nprev
I don't know...kind of skeptical based on the context. If you drill back into the article, you'll see the source is a press release by the guy who made this thing, so this could be yet another publicity grab attempt.

Happy to be wrong, though; God knows we need as many propulsion breakthroughs as we can get!
tty
I wouldn't like the Earth to get in the way of the "exhaust" of a laser powerful enough to give a 1 g acceleration to a spacecraft. That's an awful lot of photons.....
ugordan
Right, tty. My first thought about this concept was "this will be a weapon first". I'm also very skeptical about the whole thing. Where do you get the energy for such a push?
helvick
The claims referenced by the article talk about a very low thrust in this demo - 35 micro newtons. Compare this to Dawn's 12x 0.9 Newton Ion thrusters to get some idea of how far this will have to be scaled before it can be used in similar situations to an ion drive let alone the scaling needed to accelerate anything worthwhile at anything close to 1g.

What's with the name by the way? What would a non-Photonic Laser Thruster be ? Or does this do something neat with optical logic circuitry as well as lasers to achieve its magic?

Seems neat and it seems a promising area of research despite my scepticism with regard to its imminent use in actual spacecraft but I'm not buying any shares just yet either.
nprev
Yeah. For one thing, I have to wonder what sort of power source would be required to provide enough energy to achieve 1g for a practical spacecraft, even if some evolute of this thing was capable of doing so. If you'd have to fly a nuclear reactor, then why not just use a NERVA derivative?
crabbsaline
Bae Institute & Photonic Laser Thrust (PLT)

And

Bae Institute article

it's Interesting stuff. I am looking forward to updates concerning this technology. I haven't, yet, found an article that compares ion propulsion to plt.
SteveM
The "Laser Thrusters to Mars" claim seems like a PR extensionof a modest claim to use lasers to microposition satellite constellations. The details are in this paper (I'm not certain if it's a published peer-reviewed paper or only a conference presentation). Additional similar presentations at the Bae webpage.

The system described generates thrust between two spacecraft separated by "maximum estimated distances in the order of tens of km." As such, it wouldn't be applicable to a trip to the Moon, to say nothing of Mars.

Steve
crabbsaline
For what it's worth, the Mars statement is coming from Dr. Bae himself:

QUOTE
Bae, looking forward with anticipation, observes, "This is the tip of the iceberg. PLT has immense potential for the aerospace industry. For example, PLT powered spacecraft could transit the 100 million km to Mars in less than a week."
tty
I was wondering what anyone might want a laser thruster for, but for position holding spacecraft in interferometric arrays precisely controllable micronewton thrusters does make sense. It's a rather big step to main drives for planetary missions though.....
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