Author Topic: Laser Propulsion  (Read 16947 times)

Offline nec207

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Laser Propulsion
« on: 09/21/2015 08:54 pm »
 I read today that NASA is researching laser propulsion and that may change the way we send people and cargo into space.  What is this researcher into laser propulsion? Two ways of doing it from what I understand.

1 Build a laser platform on the ground to shoot at the craft
2 Build laser on the craft to shoot out the back of the craft


I hear that NASA and some other private companies are doing researcher now into laser propulsion and so far it looks really good the research!!!

Can some one explain this laser propulsion that NASA and some other private companies are working on?

 The pros and cons of laser propulsion. And when we may have it like 15 or 20 years from now?
« Last Edit: 11/03/2015 11:41 am by Chris Bergin »

Offline mfck

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I read today that NASA is researching laser propulsion and that may change the way we send people and cargo into space.  What is this researcher into laser propulsion? Two ways of doing it from what I understand.

1 Build a laser platform on the ground to shoot at the craft
2 Build laser on the craft to shoot out the back of the craft


I hear that NASA and some other private companies are doing researcher now into laser propulsion and so far it looks really good the research!!!

Can some one explain this laser propulsion that NASA and some other private companies are working on?

 The pros and cons of laser propulsion. And when we may have it like 15 or 20 years from now?
You might want to start here
https://scholar.google.com/scholar?q=laser+propulsion+spacecraft&hl=en
« Last Edit: 09/21/2015 09:12 pm by mfck »

Offline Burninate

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Four types, all of which build big, heavy lasers somewhere easy to reach, like Earth's surface, and use them to power a lightweight remote craft:


Laser thermal propulsion - Uses the laser to heat up an inert propellant aboard a rocket, through a transparent window, so it can emit it out of an expansion nozzle like a normal rocket

Laser electric propulsion - Normal solar electric propulsion uses solar panels to gather electricity to power a small particle accelerator, an 'ion thruster'.  This simply adds laser light to supplement the light from the sun, increasing generated power to weight ratio.

Laser ablative propulsion - Very short pulses of high-intensity light are pointed at orbitting debris, vaporizing milligrams of material;  The expanding gas produces a small thrust which acts to eventually push the debris out of orbit

Laser lightsails - Like solar sails, these are big mirrors affected by photon momentum exchange, but supplemented by lasers for higher thrust to weight, this is a plausible path for far outer solar system probes.

In re: mounting it on the spacecraft - there's no point in building a photon rocket out of a laser, since a small elliptical reflector around a light/heat source is nearly as effective, and neither power generation nor lasers can ever be 100% efficient.  A photon rocket itself is only useful for missions millenia long;  In reasonable timespans, it makes more sense to use propellant, which generates much more thrust per watt.
« Last Edit: 09/22/2015 06:16 am by Burninate »

Offline NovaSilisko

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You must take into though there's a lot of groups that make up "NASA", and they study all sorts of different things. Only a tiny subset of those will ever come to fruition. It's appreciated to see your enthusiasm, though.  :)

Online Lampyridae

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Yup this tech has been researched (and tested) as far back as the 70s. I read about it in Jerry Pournelle's book A Step Farther Out. Currently, reusable rockets are the next step in cost saving - a laser launch system has a huge infrastructure cost (also R&D dollars), and the launches will still not be cheap. Maybe in 30 years we'll see some entrepreneur trying to shake up the market. NASA's role is really to stimulate growth in cutting-edge tech with an aim to helping high-tech companies later on.

Offline aceshigh

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Laser ablative propulsion - Very short pulses of high-intensity light are pointed at orbitting debris, vaporizing milligrams of material;  The expanding gas produces a small thrust which acts to eventually push the debris out of orbit

not only "debris".

Lightcraft concept, by Leik Myrabo also follows the same concept

a video in english



another video in brazilian portuguese (Discovery Channel)


and another in japanese


« Last Edit: 09/22/2015 07:22 pm by aceshigh »


Offline nec207

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Four types, all of which build big, heavy lasers somewhere easy to reach, like Earth's surface, and use them to power a lightweight remote craft:


Laser thermal propulsion - Uses the laser to heat up an inert propellant aboard a rocket, through a transparent window, so it can emit it out of an expansion nozzle like a normal rocket

Laser electric propulsion - Normal solar electric propulsion uses solar panels to gather electricity to power a small particle accelerator, an 'ion thruster'.  This simply adds laser light to supplement the light from the sun, increasing generated power to weight ratio.

Laser ablative propulsion - Very short pulses of high-intensity light are pointed at orbitting debris, vaporizing milligrams of material;  The expanding gas produces a small thrust which acts to eventually push the debris out of orbit

Laser lightsails - Like solar sails, these are big mirrors affected by photon momentum exchange, but supplemented by lasers for higher thrust to weight, this is a plausible path for far outer solar system probes.

In re: mounting it on the spacecraft - there's no point in building a photon rocket out of a laser, since a small elliptical reflector around a light/heat source is nearly as effective, and neither power generation nor lasers can ever be 100% efficient.  A photon rocket itself is only useful for missions millenia long;  In reasonable timespans, it makes more sense to use propellant, which generates much more thrust per watt.


None of the above.

What I was looking at is closer to this.

LightCraft


It would change the way we send people and cargo into space.

 


Offline Jim

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It would change the way we send people and cargo into space.


no not really.  Old non news

Offline A_M_Swallow

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{snip}
Lightcraft concept, by Leik Myrabo also follows the same concept


To achieve LEO the spacecraft has to get to very high and gain an enormous horizontal speed. For what amounts to a propeller gaining horizontal speed in a vacuum will be difficult.

Current balloons have reached 53 km (32.9 miles). There may be customers for a product that can hover higher than that, which costs less than a sounding rocket and Virgin Galactic's suborbital craft.

Offline aceshigh

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{snip}
Lightcraft concept, by Leik Myrabo also follows the same concept


To achieve LEO the spacecraft has to get to very high and gain an enormous horizontal speed. For what amounts to a propeller gaining horizontal speed in a vacuum will be difficult.

Current balloons have reached 53 km (32.9 miles). There may be customers for a product that can hover higher than that, which costs less than a sounding rocket and Virgin Galactic's suborbital craft.

I did not post my thoughts or any judgement on the proposal, just the videos and article links. Anyway, some of the newer articles talk about an "evolution" of Myrabos concept, which sends to have it's own fuel which the laser hits to explosion

I agree that the original concept either shows Myrabo confuses an orbit with height or that he somehow thinks his device is aerodynamic enough to accelerate to 28 thousand kilometers per hour in dense atmosphere...

Offline nec207

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It would change the way we send people and cargo into space.


no not really.  Old non news

Sorry but what do you mean by this? That this is old article I was reading? And NASA is no longer doing research?

That this is old and this research is over?


Offline TrevorMonty

Escape Dynamics are design a LV that uses Microwave beamed power to heat hydrogen, giving a 750 ISP. This is similar to one of NASA Laser systems. Don't know how financially viable it is, requires quite a large outlay for the ground station. 

http://spacenews.com/startup-makes-progress-in-beamed-propulsion-for-reusable-launch-vehicles/

Offline Burninate

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So it turns out this stuff is mostly available on library genesis.  After reading a number of his papers:

Leik Myrabo is a cool guy who managed to weasel his way into sustaining fundamental science research after the failure of Star Wars, but he was never really a launch vehicle designer.

He investigates propulsion technologies as theoretical constructs without regard to realistic numbers, and it seems most of them stem from the question "So what else could you do with an arbitrarily powerful laser?".  He demonstrates that the equations or models for his idea work to some detectable effect under very specific conditions in the advanced wind tunnels he has access to, and then he moves on.  Then he and his followers bunge them together into one 'visionary' concept for a flying saucer without regard to actual numbers.

The small-scale hardware units he did tests on seem to be designed as a laser-heated VTOL pulsejet, with no ablation, just a shroud onto which the laser is focused, which heats the air to produce a modest thrust to weight ratio.  This is not likely to scale very well due to fundamental geometric constraints, and material science problems with very hot surfaces in a nitrox airstream;  It's also fundamentally a VTOL aircraft, not a launch vehicle.

This is fairly nice, but more on the scale of electrostatic lifters than rocket engines or airplanes.

The concepts for an actual spacecraft seem more invested in the shape of a flying saucer than any particular feasibility study.  Over and over again power levels are contrived in such a way that electrical propulsion is a feasible way to move air - gigawatts or terawatts invested in creating shockwaves out of thin air & lasers to push the vehicle, creating shockwaves out of thin air and lasers to move the air out of the way to reduce drag ahead of the vehicle, bending the shockwave electrostatically, and all sorts of crazy stuff.

This is the sort of person an enlightened country employs on the very small chance that one out of a hundred of his serendipitous ideas turn out to be practical, but I don't think any of them did, and it *seems like* his launch vehicle propulsion work is more of a portfolio than a project, because it employs most of them.  That's why the websites I've looked at before were barely legible, reading like a parody of a technical proposal, shifting fluidly from one technology to another without a clear indication that the author recognizes they're talking about several different things.

That's not to say I'm a skeptic of the general principle: I think there's a pretty safe case to be made that laser-electric accelerated orbit raising or laser thermal-jet aircraft could be done on a small scale for a few tens of millions of dollars;  that laser-thermal-thruster upper stages could be productive for a few tens of billions of dollars;  That laser-thermal-thruster vertical launch or laser-thermal-scramjets are a medium-term possibility.  Laser power just keeps creeping upwards.  I just don't see any breakthrough capacities in Myrabo's proposals.

Escape Dynamics are design a LV that uses Microwave beamed power to heat hydrogen, giving a 750 ISP. This is similar to one of NASA Laser systems. Don't know how financially viable it is, requires quite a large outlay for the ground station. 

http://spacenews.com/startup-makes-progress-in-beamed-propulsion-for-reusable-launch-vehicles/

Escape Dynamics' plan is much simpler and more decipherable;  The difference between microwave and laser beamed power is minimal for our purposes, whichever works better.  They're beaming power to heat fluid which is expelled out a nozzle in the rear.  I'm sort of skeptical that a single stage vertical launch vehicle is the best place to start, however;  The numbers for base stations are much more favorable for upper stages of reusable first stages, upper stages of impulsive or air-breathing first stages, & air-launched single-stages.  Start out high and you need far fewer base stations, start out fast and they don't need to be as powerful.
« Last Edit: 10/11/2015 09:56 am by Burninate »

Offline nec207

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 I just checked their company website, they are not reporting any recent developments at all. The most recent event I found was the publication of a book about LightCraft in 2004. They do mention having developed computer software to model flight control characteristics, there is no mention of any actual flight experiments beyond the ones in 2000 that you provided the link to. My guess is that not much work is being done anymore.




http://www.lightcrafttechnologies.com/media.html

LightCraft by Leik Myrabo by a small private group of people.
 

 It was to radically change the way we send people and cargo space.

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