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Modular Laser Launch Systems
BerntB writes "I don't think Jordin Kare's NIAC article has been covered? It's about using new laser tech to build modular
laser launch systems. The modular nature makes it easier to test and build. The only other launch ideas as cool are the Orion Project and the space elevator."
cheap labor conservatives - they want to keep you hungry enough to be thankful for minimum wage.
a) the vehicle may blind by reflected light at a considerable distance (100m - 1km or more- think of the wildlife [handwring]).
b) it ideally uses pure liquid hydrogen fuel; this means that the fuel tank ends up pretty heavy relative to the fuel (heavier than the space shuttle, because the Space Shuttle tank also holds LOX, so the average propellent density is rather better.) The ratio of the vehicle weight full/empty is critical in a high performing rocket- so this rocket doesn't perform as well as you would hope- it's not a SSTO solution, not quite, so he has a drop tank or two.
c) got a few billion? The lasers are very expensive... note that conventional rockets can be designed for *well* under a billion if you don't do anything fancy (see SpaceX)
d) it works best when you are launching a lot, but then again, just about any launch system gets cheap real fast if you launch a lot; and this one is expensive up front, so you have to launch even more to offset this.
Still, it's a very cool idea, and he's still working on it. But I can't shake the feeling Jordin has missed something that will move the idea up one more notch.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Kare, who's been plugging this idea for decades, writes "A rule of thumb for laser launchers is that the unit payload is 1 kg per MW of laser power." The Apollo lunar module (all the stuff that went to the moon) massed about 6500 Kg, of which 2500Kg made the round trip. So we're going to need several gigawatts of laser power for a moon shot.
Kare is talking about using continuous diode lasers in the 1KW range. These don't exist, but 60W units are available, so this isn't totally unreasonable. Kare proposes to use maybe 150 of these future 1KW units in a prototype. That only launches a 150g craft.
Launching something the size of the Apollo lunar module would take six million such units, and about 12 gigawatts of electrical power for several minutes. This is twice the power output of Grand Coulee Dam, the biggest single power source in the US.
The power storage problem might be overcome using ultracapacitors. You can get 2600 farad capacitors (not ufd, farads) at 2.5V today, and you can take current out fast. Auto engines can be started with six of these things, weighing a total of about 3Kg. With a big budget, a laser launch system could have enough energy storage to do the job.
Six million lasers, though, is a bit much. The prototype doesn't put enough mass in orbit to be useful, and the real version is too big.
If you want to launch a microsat, you call Orbital Sciences Corporation, and they launch a Pegasus rocket from a L-1011 for you. The X-prize guys get all the press, but Orbital actually puts stuff in orbit. They've launched 45 payloads so far. Click here for their user manual.
Project Promethius
Promethius is not a launch solution. It's a nuclear powered Ion Drive. Energia Vulkan, Sea Dragon, and the Gas Core Nuclear "Liberty Ship" are all cool launch solutions he forgot.
Javascript + Nintendo DSi = DSiCade
Dean Ing's "The Big Lifters" talked about this 15 years ago, with a prototype unit that used a maglev train to push the orbiter to just about transsonic, a short-lived ramjet booster to get upright, then hit it in the @$$ with a laser to get to orbit.
Ing talked about other interesting transportation options in that book, such as delta dirigibles to handle cargo off-load from moving trains, and engineering trucks for intermodal hauling over short distances that are better at city driving than highway. Good socioeconomics for hard sci-fi.
Design for Use, not Construction!
You are wrong.
LH tank weight is exactly the same problem with both shuttle and this approach (using LH as monopropellant + laser heating).
The main limitation of rocket propulsion is the weight of the oxidizer. Even with LOX (most weight-efficient oxidizer) the weight of the oxygen is 8x higher than the weight of hydrogen. And you need lotsa fuel/oxidizer to lift the weight of the fuel/oxidizer, etc. Any weight savings will greatly reduce the overal rocket mass and size.
Compared to shuttle (without SRBs) you would be flying the laser/hydrogen rocket with about the same tank of LH but without oxydizer.
If opportunity came disguised as temptation, one knock would be enough.
3^2 * 67^1 * 977^1
The original post said hydrogen with 2 protons per molecule which is true since hydrogen is normally found as H2 with two atoms bonding to form a diatomic molecule.
Someone didn't read the original post...(Shame too, 'cause the post is correct it just corrects something that was never said).
"When you sit with a nice girl for two hours, it seems like two minutes. When you sit on a hot stove for two minutes, it
That is some really cool stuff. I had trouble with the link there, here's the article I think you are refering too:
Riding the Highways of LightBasically, there are two types of laser rocketry, as defined by fuel: air-burning, as used by Dr. Leik Myrabo and has been seen on tv; and soild fuel (usally a dense metal) burning, as being developed by Dr. Andrew Pakhomov at the University of Alabama in Huntsville. The problem with the Myrabo method is that the laser is tuned be absorbed by the air, and thus is inefficent over long distances. Ablative laser propulsion doesn't have this problem. It is however still very much theoretical: I've seen their first fight model; it's 3/4 of a cm tall...
;)
More info on Dr. Pakhomov: pakhomov.uah.edu
Simon