Posted on 09/10/2007 11:31:01 AM PDT by LibWhacker
TUSTIN, Calif., Sept. 7, 2007 -- An amplified photon thruster that could potentially shorten the trip to Mars from six months to a week has reportedly attracted the attention of aerospace agencies and contractors.
Young Bae, founder of the Bae Institute in Tustin, Calif., first demonstrated his photonic laser thruster (PLT), which he built with off-the-shelf components, in December.
The demonstration produced a photon thrust of 35 µN and is scalable to achieve much greater thrust for future space missions, the institute said. Applications include highly precise satellite formation flying configurations for building large synthetic apertures in space for earth or space observation, precision contaminant-free spacecraft docking operations, and propelling spacecraft to unprecedented speeds -- faster than 100 km/sec.
“This is the tip of the iceberg," Bae said in a statement from the institute. "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.”
Bae founded the institute to develop space technologies and has pursued concepts such as photon, antimatter and fusion propulsion for more than 20 years at SRI International, Brookhaven National Lab and the Air Force Research Lab. He has a PhD in atomic and nuclear physics from UC Berkeley.
Several aerospace organizations have expressed interest in collaborating with the institute to further develop and integrate PLT into civilian, military and commercial space systems, Bae said, and he has recently been invited to present his work by NASA, JPL, DARPA and the Air Force Research Laboratory (AFRL).
Franklin Mead, a senior aerospace engineer at AFRL, said in a Bae Institute statement that the PLT demonstration and measurement of photon thrust is "pretty incredible. I don’t think anyone has done this before. It has generated a lot of interest."
The institute said Bae’ paper, “Photonic Laser Propulsion: Proof-of-Concept Demonstration,” was recently accepted for publication this year in the American Institute of Aeronautics and Astronautics' Journal of Spacecraft and Rockets. It documents how he overcame the inherent inefficiencies of traditional photon thrusters in generating thrust by amplification with the use of an innovative optical cavity concept.
"For decades, rocket scientists have tried to overcome the inefficiency of photon thrusters by amplification based on optical cavities separated from laser sources, but failed," the institute said. "In contrast, Bae’s PLT (patent pending) places the laser medium within a resonant optical cavity between two platforms to produce a very stable and reliable thrust that is unaffected by mirror movement and vibration -- ideal for spacecraft control or propulsion."
Bae will present at the AIAA SPACE 2007 Conference & Exposition, to be held Sept. 18-19 in Long Beach, at four sessions: Space Transportation Systems, Promising Space Concepts from the NASA Institute of Advanced Concepts (NIAC), Space Systems for the Next 50 Years, and Advanced Vehicle Systems.
The PLT research was partially funded by NIAC (NASA Institute of Advanced Concepts) as part of a spacecraft formation flight concept grant.
The bad news is it works just like the flux capaciter and requires 1.26 gigawatts to run.
No, it wouldn't. They said that they would get you there in a week. Nothing about you being in any shape to ever come back. Just keep on accelerating until impact.
In the simple case of a constant force (assuming a constant mass):
x(t) = x_0 + v_0t + 0.5 * a t² (x_0 and v_0 are assumed to be zero)
a = 2*x(halfway)/t² = 2*50e9 m/(3.5 days)² = 1.09 m/s²
This is about 1/9th of a g. If they had the capability to have 1 g of acceleration then the transit time would only be 56 hours (1/3 of a week).
Oh, I should also mention that since power equals force times velocity, it probably wouldn’t be feasible to be able to power the thrusters after the beginning of the trip so the initial forces will have to be much higher.
Err, I mean that the thrusters will have the same power applied, but will lose thrust the faster you go, so your initial thrust has to be much higher than the lower thrust (using the same power) later in the trip (because KE = 1/2 mv² and you have to pay 4 times the energy for every doubling of velocity).
Whatever mass you're kicking out of the back of the vehicle is accelerated relative to the vehicle. No matter how fast the vehicle is going, if the mass-flow-rate and the delta-v is the same, the thrust produced is the same and the energy cost is the same.
Once you go warp, you’ll never look back.
“That was just his desktop prototype. He says it’s scalable.
But I have a lot of doubts about it myself. We see too many of these too-good-to-be-true scams.
But... IF it’s real... OH, BOY!”
Maybe, just MAYBE, I’ll get to visit Mars before I die, after all.
Old Student <————CROSSES FINGERS REAL HARD!
“If it was built by using “off the shelf parts” then it’s not patentable, IIRC.......”
Which means anyone who could read the blueprints could build one. (Given the cash, of course.)
Power to the People! ;)
I can see a LOT of people taking off on their own. Also a lot of debris fluttering down...
You do not conserve energy in your case. KE = 1/2 mv². The higher the velocity, the higher the cost per incremental change in velocity. Since, P = F * v, your rocket would become much more powerful the faster it goes if it had a constant force. Does it make sense to you that an object that hasn’t changed its mass becomes more powerful the faster it goes when it is only powered by a constant power source?
Oh, and before you mention it, an accelerating body is, by definition, not in an inertial reference frame. So your Galilean transformation arguments do not apply.
Feel like weighing in? ;)
That depends, actually -- space is funny that way. We used to model continuous thrust forces of 0.05 lb for the Shuttle (which weighs 225,000 lb). That's a tiny acceleration, but very noticeable over the course of an orbit.
If you can keep even this small thruster firing for long periods of time, it adds up to a lot. Of course, it really all boils down to power: how much does it take to get this mouse-fart thrust?
They have no rest mass. But they have a small mass by virtue of the fact that they have energy:
Ephoton = mc2, so m = Ephoton/c2
And they have an exhaust velocity = c.
Thrust = mass flow rate * exhaust velocity. So if you have some number N photons per second, then
T = NEphoton/c2 * c = NEphoton/c.
I don't rightly know how you'd count photons, but it occurs to me that NEphoton is the total photon energy flux, so you don't really need to count photons, you just need to know the photon energy output by the thrust "beam".
Uh, no. a = 35e3/1e6 = 35e-3 m/sec2.
It would take about 28.6 sec per meter per second -- so a day's thrust would give you around 3 km/sec of delta-V.
Interesting!
F=ma
F = 35 µN
m = Mass of your spacecraft
Solve for a!
(Hint, not a lot of G’s, but you don’t need a lot as long as the acceleration is constant for a long period of time...)
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