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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."
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.
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.
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.
They didn't say you would get there alive. They just said you would get there in a week.
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.
nasa knows how to stop things at mars, that's easy. (think: "feet, meters, same difference")
I did quite a bit of reading on spacecraft propulsion recently (specifically Nuclear pulse propulsion 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.
It includes turnaround at the halfway point.
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
"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."
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.
Do you currently find 1G uncomfortable?
Semi-automatic amateur armchair Australian philosopher; conjecture ready at any moment...
That was funny, I'll give you that one. I am an idiot.
Survival isn't necessary. Just get your ass to Mars. G-G-Get your ass to Mars.
I hate printers.
His demonstration thruster produces 35 micronewtons.
.0005467722 Km/s^2 = 64 milligrams, so if we were using this to power a marscraft with the mass of the acetominophen contained in a single extra strength tylenol tablet, it would be more than 10x too heavy. Of course they said it could be scaled up, but that's a heckuvalot of scaling.
35 micronewtons /
I doubt the smallesst possible manned Mars vehicle could be less than 1,000kg. That's a scaling factor of 15.6 million. I can jump over 3 feet on the trampoline in my back yard, which translates to a maximum velocity of 4.23 m/s. If I scale that up by 15.6 million, I would be launching myself at 66,000,000 m/s, far exceeding escape velocity, and reaching Mars under my own power in under 30 minutes.
You must have forgotten that nuclear power, by definition, harms the environment.
That's just how it works.
There's no environment to harm in space so nuclear power can't possibly work out there.
IOU one (1) signature
voila! sublight speed!
Big deal. I have sublight speed sitting at my desk.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
- That the grandparent post was funny.
- That you are an idiot.
Both of these could reasonably considered informative, however the second is likely untrue, since in my experience idiots are quite likely to be the last to realise, and the moderation totals on the grandparent would have informed even the most humour deficient. Or are moderators now giving karma to people who admit their errors? If so, have I accidentally logged into some kind of bizarro-Slashdot, where everyone is polite and respectful? And is there a way of making sure I don't accidentally end up on the other one again?I am TheRaven on Soylent News
But what about the heat? It's quite difficult to cool off lump of metal in a vacuum without discarding hot material to do so. Even if you could feasibly power a craft to Mars with this, how would you stop yourself from arriving as Astronaut McNuggets?
Our chief scientist, Davros McDonald, has calculated the ultimate evolutionary form of the human race to be McNuggets. Why do you struggle against progress?
echo -e 'global _start\n _start:\n mov eax, 2\n int 80h\n jmp _start' > a.asm; nasm a.asm -f elf; ld a.o -o a;
The concept of external (i.e. explosions are not contained within the ship's structure) nuclear pulse propulsion was actually studied in the late 50s, early 60s as Project Orion (internal NPP, which is like your car analogy but with nuclear explosions instead of fuel-air explosions, places too great of a stress on the ship's structure to be feasible).
... it was a combination of quite a few political reasons:
They never did get enough funding for a test with a nuke, but they did build 1-meter scale models powered by RDX charges. Powered by I believe 6 explosive charges, one of these reached 100 meters in a controlled test flight, proving that the concept worked (at least with lower energy pulses). As for whether or not it would work with nukes, their numerical modeling strongly indicated that it would.
You mentioned that the blast wave might be moving too fast to be useful, but actually that's the whole point - the impulse of the blast wave impacting against and then rebounding off the back of the spaceship is what provides thrust, so the faster the blast wave is moving, the greater the impulse and thrust.
Of course, the spaceship would have to be stupidly large to survive the instantaneous acceleration, but that was why it was so attractive. A ship around 10000 tons could've made it to Pluto and back within a year. Plus, it had a very high thrust-weight ratio, which meant that the fraction of the weight that was useful payload was stupidly high as well.
So then if NPP is so good, why was the project killed? It wasn't because it didn't work
1) NASA had thrown its support behind the competing NERVA rocket.
2) Fallout was problematic.
3) There was no mandate from Congress for missions that would require such performance, and NASA had no desire to dictate policy.
4) Partial Test Ban Treaty of 1963 banned all above-ground nuclear testing.
Remember, there's a big gap between "likely untrue" and "always untrue." When someone can look at their own statement, realize what it implies about their capacities, and then confidently declare "I am an idiot," they are displaying insight that is well above average, and certainly deserving of mod points.
I, for one, welcome our new self-insight-possessing commenters.
I'm an idiot, too.Singularity: a belief in the "God" idea with the "demiurge" relation inverted.
The current space shuttle seems to deal with the heat from explosives fairly well in the atmosphere and in space. They use a model called "let's not put it next to the astronaut's faces".