Photonic Laser Thruster Promises Earth to Mars in a Week

serutan writes "Using lasers to drive spaceships has been a subject of interest for many years, but making a photonic engine powerful enough for practical use has been elusive. Dr. Young Bae, a California physicist, has built a demonstration photonic laser thruster that produces enough thrust to micro-maneuver a satellite. This would be useful in high-precision formation flying, such as using a fleet of satellites to form a space telescope with a large virtual aperture. Scaled up, a similar engine could speed a spacecraft to Mars in less than a week."

You can't go home again

[Harmonious Botch (921977)]

...we fried it duing liftoff.

acceleration?

[OrangeTide (124937)]

What sort of acceleration would that be? Would it be multi G-force worth, that might be impractical for humans.

Re:acceleration?

[scoot80 (1017822)]

They didn't say you would get there alive. They just said you would get there in a week.

Re:acceleration?

[Harmonious Botch (921977)]

About 1/2 G.

Re:acceleration?

[Score Whore (32328)]

Half a G will get you way further than Mars in a week. The greatest distance between Earth and Mars is 391 million Km. Assuming you're going to go constant acceleration half way and constant acceleration in the other direction the second half of the trip, 1/2 G acceleration will get you 897 million Km end to end in seven days.

If you don't mind going through the Sun, that 1/2 G will get you Earth to Jupiter, in the worst geometry possible, in seven days and one hour and thirty minutes.

Re:acceleration?

[Harmonious Botch (921977)]

It includes turnaround at the halfway point.

Re:acceleration?

[AKAImBatman (238306)]

As I recall, the computations for reaching Mars in a week were predicated on One-G acceleration. i.e. Earth normal gravity for a ship in transit. To slow down, you simply spin the ship at the halfway point and accelerate in the opposite direction.

If (and I stress *if*) this invention is not so much hyperbole, it could change the face of space travel forever. We could build interplanetary starships (in this context, ships that never land on a planet) that would be limited only by their power-generation capabilities and not by their reactive fuel. Which means that we could build a ship with a large nuclear powerplant on board, and it could cruise the solar system for as long as its Uranium/Plutonium fuel held out.

Of course, we still need to solve the problem of high cost of launch, but that little issue would be easier to solve if we actually had somewhere to go once we got in orbit. Scaling up the number of launches would almost certainly bring the price per launch down. In fact, the reason why the Space Shuttle never reached its promised price-per-kilo is because it was predicated on regular launches that never materialized. Starships could change all that. Especially if the cost of moving personnel and equipment was marginalized by carrying more of them per trip.

For example, I always figured that a special module could be fitted to the Shuttle's cargo bay to carry as many as 60 people to the ISS. Given that the Shuttle has to be man-rated for flight, carrying people makes a lot more sense than hauling around equipment that's better served by a Delta or Atlas rocket.

How exciting! And probably too good to be true.

Re:acceleration?

[Hucko (998827)]

Do you currently find 1G uncomfortable?

Re:acceleration?

[scoot80 (1017822)]

That was funny, I'll give you that one. I am an idiot.

All a matter of scale...

[Microlith (54737)]

And if scaled up, cockroaches run at 800mph and fleas could jump over a mile. However, the increase in mass and energy requirements would make it impossible.

Small scale thrusters using only lasers is a good start, but we'll have to see what else gets bigger with scale, other than just the thrust.

Re:All a matter of scale...

[iamhassi (659463)]

"we'll have to see what else gets bigger with scale, other than just the thrust."

That's what she said ;)

The Warriors

[PresidentEnder (849024)]

At least now we'll have a way to beat the Kzinti [wikipedia.org] when we make first contact.

I smell bullshit

[Rix (54095)]

The Bae Institute was founded in 2002 by Dr. Young K. Bae

In other words, no existing institution would accept the good doctor, so he made his own, and issued a press release written in false third person.

Re:I smell bullshit

[s4m7 (519684)]

In other words, no existing institution would accept the good doctor, so he made his own, and issued a press release written in false third person.

http://www.photonics.com/content/news/2007/September/7/88894.aspx [photonics.com]

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).

Lasers are better with Photons...

[fahrbot-bot (874524)]

Photonic Laser Thruster

Muuuuch better than using those LASERS without Photons.

[I hear that adding the photons also makes them lighter...]

Energy source?

[StefanJ (88986)]

Where is the energy coming from to create those photons?

Since you're dealing with a photon drive, the reaction mass usage (as determined by the classic rocket equation) is going to be negligible for the speeds required for interplanetary travel.

In fact, I'm not sure what the reaction mass would be in this case.

But in any case, you're going to need a lot of energy to create that photon thrust. Great phrigging big reactors, which means great, great, phrigging big radiators since you don't have the luxury of a river to carry away your waste heat.

Antimatter might be a compact way to store the required energy, but converting the gamma rays from matter/antimatter reactions to electricity is going to require heat exchangers and great big radiators as well.

Well, anyway, scaling this up is going to involve several bears of a problem.

Also, please note that this "article" is a press release from the guy who made the invention.

Re:Energy source?

[Arabani (1127547)]

I did quite a bit of reading on spacecraft propulsion recently (specifically Nuclear pulse propulsion [wikipedia.org] and basically what I got out of it is that if you have a massive energy source (say, antimatter) you're better off just blowing it up and riding the blast wave. You can get extremely high thrust AND specific impulse that way, which is not possible with almost any other engine technology (either high thrust and low specific impulse like chemical rockets, or low thrust and high specific impulse like ion engines). NPP (and its derivatives) is basically the best way we know of right now to get high enough performance for interplanetary, or even interstellar, missions.

NPP originally started with using nuclear explosions, but more recent research has focused on inertial confinement fusion and even antimatter-catalyzed fusion. The obvious extreme is using antimatter-matter detonations and riding the blast wave, which I'm fairly certain would be more efficient and yield better performance than taking that energy and pumping it into a laser.

Scaling up is fun

[suv4x4 (956391)]

I wonder why we don't just scale up a bridge right to Mars and drive to there with a drag racer car. If the latter is too slow, I suppose no problem, we can scale it up as necessary.

Re:How "scaled up" is this?

[Mothinator (1103295)]

It only says it can get the spacecraft to Mars in a week. It does claim to be able to stop once it gets there.

Re:How "scaled up" is this?

[Dachannien (617929)]

Actually, it says that it can get the spacecraft to Mars in a week and can stop once it gets there. But it doesn't claim that anyone will survive the impact.

Re:How "scaled up" is this?

[MrNaz (730548)]

Survival isn't necessary. Just get your ass to Mars. G-G-Get your ass to Mars.

Re:How "scaled up" is this?

[azenpunk (1080949)]

nasa knows how to stop things at mars, that's easy. (think: "feet, meters, same difference")

Re: Metric Joke

[Telephone Sanitizer (989116)]

A harsh lesson that I have learned here...

If you're going to make a lame joke, at least include a cite so there's a chance of getting modded up as "informative."

The Mars Climate Orbiter:
http://en.wikipedia.org/wiki/Mars_Climate_Orbiter [wikipedia.org]

"The Mars Climate Orbiter was intended to enter orbit at an altitude of 140-150 km above Mars. However, a navigation error caused the spacecraft to reach as low as 57 km. The spacecraft was destroyed by atmospheric stresses and friction at this low altitude. The navigation error arose because a NASA subcontractor (Lockheed Martin) used Imperial units (pound-seconds) instead of the metric units (newton-seconds) as specified by NASA."

Power = Thrust * Exhaust Velocity

[roystgnr (4015)]

To send a ship to Mars in a week, Thrust should be roughly 10m/s^2 times the ship's weight, which we'll say is only ten metric tons. (Because we're getting there in a week, we can pack light... pack light, get it? I slay me.) That gives us 10^5 Newtons of thrust.

Exhaust Velocity is the speed of light, or about 3*10^8 m/s.

So our power consumption is 3*10^13 Watts.

By comparison, the USA is currently consuming less than 1*10^13 Watts on average.

In other words, if think you think it costs too much to refuel an RV now...

It's not completely implausible to use light to propel a spacecraft, but either that propulsion will be ridiculously slow (e.g. solar sails, laser sails, or the "precisely tweak your satellite's orbit a tiny bit" applications mentioned in the article), or it's going to require ridiculous "cheap antimatter" amounts of energy.

Re:Solar system escape velocity!

[AKAImBatman (238306)]

So anyone riding the spacecraft better hope that there isn't a malfunction of the "slowing down" laser at the other end, as depending on the angle, that might be enough to exit the solar system altogether!

The article calls this a "Photon Thruster". What that means is that the device would be mounted on the vehicle as a thruster rather than the vehicle "riding" a laser-beam like in Beam-powered propulsion [wikipedia.org]. So as long as the laser restarts after you flip the ship, you're good to go.

Note that this is a separate issue from powering a laser cluster large enough to reach Mars in a week...