Beamed Propulsion Trajectory

Void · 2013-11-15 09:12:43

Void, you may not agree with me-- and that's fine! I'd encourage you to state your disagreement if you don't agree, because I'm far from being right all the time.

OK, thats fine, it's better to find truth than to continue in ignorance.

However, if beamed power with lasers has any merit, then would it be possible to beam power to an attachment intended for that purpose, and not a rocket engine? Then having the hybrid capability that way. Of course the beamed power must be able to lift the attachment, and to make it worth anything it must provide a surplus of lift to add to that of the rocket.

If you are completely negitive to this then I would have to conclude that beamed power by laser is not a possibility.

Supposing that lifting a device with lasers is theoretically worth considering;
I will point out that if beamed power to a device without a chemical (Or altenative) lift has it's own problems. Clouds for instance.

But yes any device which has not been produced yet has lots of unknowns, and I am sure that there was a time when many people thought that chemical rockets could never do what they do now.

GW Johnson · 2013-11-15 10:20:10

There's a vast difference between scientific feasibility and engineering practicality, measured in tens of millions, if not billions, of dollars. I seem to recall some feasibility experiments were done a few years ago regarding laser beamed propulsion. I don't recall anything ever being done with a flying vehicle.

The tracking and pointing problem for laser propulsion is far more difficult than a "simple" laser weapon. You have to hit a specific point on the "engine" (whatever it is) without wandering off-target at all. With the weapon, anywhere on the (mostly tankage) vehicle will do. To the best of my knowledge (admittedly short in this topic) we don't yet have that kind of pointing and tracking ability yet.

The Isp numbers being bandied about in this conversation do indicate that it might be worthwhile to attempt the development of that kind of pointing and tracking ability. Although, it enables the laser weapon at higher effectiveness, as well.

GW

Void · 2013-11-15 11:23:00

Here is a reference to that GW:

http://en.wikipedia.org/wiki/Beam-power … ed_systems

http://upload.wikimedia.org/wikipedia/c … tcraft.jpg

I guess I will continue even though it is above my level

For a pulsed laser;
1) Have the rocket communicate it's position per gps on a continuing basis. Also send other information such as how atmospheric conditions (wind) are affecting the path and future predicted location of the rocket.
2) Analyze the atmosphere for twinkle per a low powered signal laser as is done for astronomy
3) Alternate pulses. First a signal pulse to confirm pointing is good, followed by a power pulse, if the results are confirmed as good.

In the case of delivery to a non-chemical engine, it might be possible to fine tune the reciever with actuators, to displace it an inch or two.

By this method successful delivery of power pulses would be facilitated. As it would be a chemical rocket intended to go to orbit if necessary without any successfully delivered power pulses, missing out on some would not be a problem.

Also, if the duration of a pulse were short, the actual delivery of a power pulse to a unintended part of the rocket might be survived, because actual damage might require a long set of power pulses being delivered to the wrong spot over a short period of time.

Of course the higher in the sky you got, the longer the communication time lag, which would make it harder, so for this reason (And others) there would be an altitude and distance limitation to it.

JoshNH4H · 2013-11-15 14:25:45

Void-

With regards to hybrid propulsion, it's not impossible. I just don't think that it's a good combination of the two systems because you're adding complexity for what sounds like a small gain in performance. If you have a more significant gain in performance, I'd question why you're not using beamed propulsion in place of your chemical rockets, since it will likely have much higher performance, and if it can handle the whole mission (even if it's an order of magnitude, it's probably worth scaling your power system up and/or your payload size down).

By the way, GPS gives a standard error of 5 m, and won't work at speeds above 565 m/s. That means it's probably not a good resource for this.

GW-

That's the benefit of pointing straight up, IMO. You only have to really calibrate the pointing once, and reorient it occasionally afterwards. You don't need to move anything with high precision, just construct it precisely and fix it every once in a while to account for mechanical/thermal loading.

I don't claim that this will give perfect accuracy. But from there, the rocket can actually do the maneuvering. I would expect that the rocket would look something like a normal rocket, but with a parabolic dish at the bottom, reflecting and focusing the light towards a heat transfer chamber region. The larger the dish is, the more leeway there is in terms of being off the mark during launch. Presumably the beam will be most intense at the center and less intense on the outsides, and by having some way to tell the temperature of the mirror it will be possible to determine the position of the rocket relative to the position of the beam. It's also conceivable that there could be a much lower intensity guide laser.

I wouldn't be too worried about clouds, really. The beam intensities are likely so high that they will simply burn through any clouds in a fraction of a second. The bigger issue would be moisture/condensation, but I would expect that the beam could be turned on before launch to clear any moisture out of the way.

Void · 2013-11-18 11:13:37

Why?

As a laboratory for the development of instrumentation. Just because it is not good enough now does not necessarily stop it from being improved.
First you perfect your instrumentation, your laser point system.

FYI (Strike GPS, substitute, Local Postioning Systems/Instrumentation/A camera on the rocket looking at Eor, owl, Christifer Robin, and Poo Bear waving flags on the ground.)

Then bring back GPS, because it may still be useful at some point bring it back as a future better GPS.

And if you tell me that it is impossible to point a laser at a machine, then of course it is impossible to
communicate with a spacecraft orbiting the Moon.
http://www.space.com/23308-nasa-moon-la … ecord.html

Then the chemical rocket as a laboratory to study the transmission of power by energy beam to a moving object.
Laser, use the more generic “energy beam” phrase, which also allows lasers).

A chemical rocket is a moving object and moves similar to how a moving object projected by an energy beam might move.
Therefore you can build a very small scale version (Laser pointer) to test the process and define it's potential. If the results seem positive, you can scale it up by increments as far as the reality of physics and economics will allow.

It is possible that you would eventually eliminate the chemical rocket characteristic and then have an energy beam only method, but as far as I am concerned "Why would you want to do that?". An energy beam to project a machine upwards still needs working mass, which you must either carry with the machine, or draw from the atmosphere. Drawing from the atmosphere comes to fault where it gets too thin.

So, if you are carrying mass in the machine for the beam to heat up, and you have a choice for that mass to carry chemical energy with it. Such machines have already been made (Chemical Rockets). So you have this mass which can be burned to produce thrust, and you can also project more energy into it.

As for engines not being tolerant of this, I said "I don't think existing engines could put up with this very well". Then you told me that "A space shuttle engine would not put up with it very well".

I say again true, that is my expectation as well. But of course do the experiment on a very small engine. One that can be throttled back.
Throttle it back, but try to bring the thrust level back up by adding energy from a power beam. Is the engine going to perform well? No it is an existing engine which was designed for a specific purpose. However, you might learn something about designing an engine that could operate in both modes.

Mode 1: 100% chemical energy for situations where the power beam failed or was not convienient to use.

Mode 2: 50% chemical energy + 50% power beam for situations where the power beam was on line and functional. I have previously stated a limit of 5,000 to 10,000 feet, but that was arbitrary, maybe it works 5,000 to 10,000 feet and you want to attempt to expand it upwards.

Why is this worth doing? Because you might conserve propulsion mass if Mode2 is functioning well, and be able to bring it up to orbit along with your other payload. It might be worth a buck or two, should it be possible to apply it to a value added service.
And finally it has been stated by that guy that owns space X, that the hardware is more valuable than the fuel. And so they are trying to figure out how to recover booster stages.

The scheme listed above also has the potential to recover the hardware by either getting it up to orbit, or landing it on the surface of a world.

If it is power beam alone, I have a hard time figuring out what the abort modes exist that could recover the hardware.

As for economics, it seems that I have to jump through that hoop more than anyone else (Or maybe that's just my perception).

Could you get your fuel from the Moon cheaper? Maybe, but then you could also use a hybrid system to get it to Earth orbits, conserving the finite amount of such fuels that can be gotten from the Moon.

Is it the only and best plan? That is not proven at all. I did use the word laboratory, which implies testing. It would have to pass quite a few tests, to displace other methods.

But keep in mind that my objective was to transfer an idea to other minds, and I have done that so, it really does not matter what further reply I get on this.

I expect I will vacate this thread, at least for a while, and so keep the peace, even so, thank you for your time and input, and I really and truly hope that you outdo lasers with your power beam concept.

GW Johnson · 2013-11-18 12:50:29

Why not combine laser energy delivery with the super-high Isp explosion propulsion concept underlying the old Project Orion nuclear pulse propulsion? Explode some on-board reaction mass with a ground-based laser pulse, so that it blasts against a pusher plate on the base of the vehicle. That kind of beam power and pointing accuracy is available today, right now. The old Project Orion team did almost exactly that back in the 1950's when they flew a 1 meter scale model with dynamite charges. I dunno what Isp is achievable, but the effective temperature of a high power laser beam upon hitting the reaction mass should be well beyond anything we might see as the chamber temperature in any imaginable chemical rocket. With shaped-charge effects on the explosion design, you can recover almost half the momentum released in the explosion.

GW

Last edited by GW Johnson (2013-11-18 12:56:44)

JoshNH4H · 2013-11-18 13:47:10

Void: My issue with your proposals is related to the implicit scalability of any physical systems. If you can make a laser capable of outputting 50% of a rocket's power, it's not that big of an advance to make a laser capable of outputting 100% of a rocket's power. This is especially true when we're already talking about a hundredfold (Approximation; No calculations done. Depends strongly on payload size, effective Isp, and what you consider to be the state of the art in lasers) increase over existing lasers.

I don't disagree that a technology development program would be needed to step up the laser power, but the way to do that would probably be on test articles of smaller size, not by adding this system to existing rockets.

GW- That sounds pretty feasible. Actually it sounds a lot like the lightcraft idea, only in that design the pusher plate and the explosive charge are one and the same, which simplifies the design significantly.

Void · 2013-11-18 14:55:36

GW I like it also. Also perhaps even more if explosive materials could come from the Moon for some space activities.

Yes Josh, your arguments have merrit, but look what happened. GW did a good one.

We do have bad natural chemestry togeather, so small doses maybe. I am vacating this thread. Have fun.

GW Johnson · 2013-11-18 15:11:56

Hi Josh & Void:

In the old nuclear Orion proposal, the reaction mass was a huge block of polyethylene on the side of the nuke charge toward the vehicle. The neutron reflector around the fission device was shaped to produce the gamma blast in two sharp spikes, one pointed toward the vehicle through the reaction mass, side/lateral gamma minimized. That's the shaped charge I spoke of.

That gamma spike toward the vehicle converts the reaction mass into super ionized plasma moving at super high velocities toward the vehicle. The pusher plate diameter subtends the entire plasma spike at the blast distance. Out in space, they were talking 1-3 KT charges to push spaceships in the 10,000 to 20,000 ton class at near 2 gees, and at Isp in the 10,000 to 20,000 sec range. It works better the larger the vehicle; their NASA-mandated small Mars design was several hundred tons and was under a miserable 5000 sec Isp.

If one explodes inert mass with a laser blast, one should be able to package the inert reaction mass in such a way as to produce the same double-spike shaped charge effect. You suddenly and catastrophically blast it into oblivion with a death ray-strength laser. I doubt it would go far into the plasma ionization range, so the achievable Isp would be far less than the nuke. WAG: 1000-2000 s Isp, or 10 times less than the big nuke Orion.

Still a pulsed explosion drive, should still be better that lighting fires inside tin cans (chemical rocketry). Ha ha.

GW

JoshNH4H · 2013-11-18 15:19:10

What benefits do you see that having relative to ablating a plate? It seems like it's more complicated but not necessarily higher performing.

GW Johnson · 2013-11-18 15:37:02

Actually should be about the same performance as direct plate ablation. At least very crudely. The difference is you don't lose the plate.

The reaction mass could be just water. Probably as ice, with carbon dust in it to make it opaque and black. It has to absorb the laser energy efficiently. Dirty ice should be cheaper to make than plastics or steel.

It'd be a bit smoky, though.

GW

JoshNH4H · 2013-11-18 23:08:48

I'd personally have no issue with the notion of a plate that popped on and off with each flight. It's sort of an intermediate between reusable and nonreusable rockets, but the manufacture would be simple and inexpensive.

GW Johnson · 2013-11-24 22:44:39

Here's a silly idea: put the dirty ice cube on the tail of the vehicle. Then just keep shooting it with the laser cannon pulses. It ought to fly by pretty much the same physics as pulse propulsion. But without nukes.

GW

JoshNH4H · 2013-11-25 22:54:32

GW Johnson wrote:

Here's a silly idea: put the dirty ice cube on the tail of the vehicle. Then just keep shooting it with the laser cannon pulses. It ought to fly by pretty much the same physics as pulse propulsion. But without nukes.
GW

Actually, I think this is pretty much what Leik Myrabo is talking about with his lightcraft proposal.

Tom Kalbfus · 2013-11-26 07:44:41

Remember the Millennial Foundation? They had a plan to build a floating Island powered by an OTEC plant using accretion of materials from seawater by electrolysis, later on they proposed building a maglev that accelerates a ship and shoots it out the side of a mountain, and a battery of lasers would track and fire on the craft hitting a dirty ice cube as it passed overhead to boost it out of the atmosphere and to orbital velocity. Their space colony was a zero-g colony, there was no rotation for gravity, people just lived in zero-gee. They stimulated their muscles with electrical shocks to prevent them from atrophying in the zero-gee environment. They also planned on building a Dyson Bubble out of solar sail material made out of the material of Mercury when its taken apart, then they planned to harness the energy to the Sun to produce antimatter by the ton to power starships and colonize other star systems, later on after trade routes are established, they'd build a maglev that is one third of a light year long to accelerate capsules at 3-gee over four months to near the speed of light and have another maglev outside the Alpha Centauri system to catch the capsule and slow it down to bring the colonists to that star system. A lot of wild ideas here, what do you think of them?

JoshNH4H · 2013-11-26 10:06:44

Wild indeed

None impossible but of course each has its own technical issues. Mostly this isn't really the thread for them, but I've been harping on why vertical launch is better than horizontal launch for beamed propulsion for the better part of two pages

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#26 2013-11-15 09:12:43

Re: Beamed Propulsion Trajectory

#27 2013-11-15 10:20:10

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#29 2013-11-15 14:25:45

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#30 2013-11-18 11:13:37

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#31 2013-11-18 12:50:29

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