NASA Study on the possibility of using Beamed Energy Propulsion for Space Launches

Originally posted by sbctinfantry
You kind of lose most of your energy when you create the beam.

Lasers aren't known for high efficiency, but then again, launching a chemical rocket isn't a completely efficient process either. At the end of the day, it's how the overall launch economics work out, assuming other issues like safety and reliability can be addressed satisfactorily.

If you could harvest 100% of the energy output, that wouldn't be an issue. You're probably looking more at least $100k a second because we all know you're only going to harness about 1% of your output unless it is a closed environment.

Wait, you just said you lose most of your energy when you create the beam. now you're saying if you could harvest 100% of the beam that wouldn't be an issue, which is inconsistent. Is the issue creating the beam, or harvesting the beam? I'm sure both are.

I thought I was pretty clear but I can see where I'm not, I'll just tell you to give me the benefit of the doubt or learn mathematics.

Where did you come up with 1%? I don't know of any hard mathematics that limits overall efficiency to 1%. If you were one of the two physicists who developed the prototype, I would defer to your expertise. However that doesn't seem to be the case.

I'm not saying this technology will work, or that it will be cost effective. It may turn out to not be practical. But an argument of "trust me, learn math" is hardly convincing when you're arguments are a little inconsistent, and you've failed to show any math I don't understand, nor do you have any idea how much math I know (which is quite a bit).

Originally posted by Arbitrageur

Originally posted by sbctinfantry
You kind of lose most of your energy when you create the beam.

Lasers aren't known for high efficiency, but then again, launching a chemical rocket isn't a completely efficient process either. At the end of the day, it's how the overall launch economics work out, assuming other issues like safety and reliability can be addressed satisfactorily.

If you could harvest 100% of the energy output, that wouldn't be an issue. You're probably looking more at least $100k a second because we all know you're only going to harness about 1% of your output unless it is a closed environment.

Wait, you just said you lose most of your energy when you create the beam. now you're saying if you could harvest 100% of the beam that wouldn't be an issue, which is inconsistent. Is the issue creating the beam, or harvesting the beam? I'm sure both are.

I thought I was pretty clear but I can see where I'm not, I'll just tell you to give me the benefit of the doubt or learn mathematics.

Where did you come up with 1%? I don't know of any hard mathematics that limits overall efficiency to 1%. If you were one of the two physicists who developed the prototype, I would defer to your expertise. However that doesn't seem to be the case.

I'm not saying this technology will work, or that it will be cost effective. It may turn out to not be practical. But an argument of "trust me, learn math" is hardly convincing when you're arguments are a little inconsistent, and you've failed to show any math I don't understand, nor do you have any idea how much math I know (which is quite a bit).

I understand you don't study physics so I'll just be congenial and explain where your errors are and you can learn something as well as get the facts right.

It is fact that our current abilities to release and harness energy are fairly primitive. If you want to start sending things into space, you are required to harness a lot of energy very cheaply. The problem with lasers is that they are run off that same primitive power grid which uses coal as it's main feul. Trade that for rocket feul and it really doesn't make a significant difference. In fact, until we can learn to harness more of the energy we create, most of it will continue to be lost in the release.

There are two issues that need to be addressed, basically. If we learn to harness 100% of our energy production, or at least close to it, we could send rockets into space much more cheaply and regularly that we do now. However, the second issue is that the actual energy in must always be mathematically subtracted from any force to overcome a few things.

First, there is friction. I'll try to use layman terms because it's the most difficult problem in introductory physics. It's called, the incline plane. Yale is offering introductory physics right now, and here's a discussion on the inclined plane.



The point you should gather is that no matter if you are going vertical or almost horizontal, there is always an inclined plane when it comes to figuring out what kind of energy is needed to move an object when the force of friction is acting on it. I'm not going to go into formulas, and the basics are that once you overcome friction, the values change, but you still have to pay the initial toll to move.

There is also inertia. The idea that objects in motion, stay in motion. Objects at rest, stay at rest. You must overcome inertia before you ever actually move. Keep in mind that this is the first force you must overcome, combined with friction. From that point forward, friction will work against you until you leave the atmosphere, constantly slowing you down.

All of this is difficult to feul, and unless we can harness near 100% energy efficiency from something like anti-matter drive engines, it's going to stay expensive. It's like saying we're greener for running electric cars. Where does the electricity go? What does it take to transport it, what's lost in transit and is the quality the same as it could be.

Anyway

If you don't know why we don't get full efficiency, just look at gasoline.

Modern gasoline engines have an average efficiency of about 18% to 20% when used to power a car. In other words, of the total heat energy of gasoline, about 80% is ejected as heat from the exhaust, as mechanical sound energy, or consumed by the motor (friction, air turbulence, heat through the cylinder walls or cylinder head, and work used to turn engine equipment and appliances such as water and oil pumps and electrical generator), and only about 20% of the fuel energy moves the vehicle. At idle the efficiency is zero since no usable work is being drawn from the engine. At slow speed (i.e. low power output) the efficiency is much lower than average, due to a larger percentage of the available heat being absorbed by the metal parts of the engine, instead of being used to perform useful work. Gasoline engines also suffer efficiency losses at low throttle from the high turbulence and head loss when the incoming air must fight its way around the nearly-closed throttle; diesel engines do not suffer this loss because the incoming air is not throttled. Engine efficiency improves considerably at open road speeds; it peaks in most applications at around 75% of rated engine power, which is also the range of greatest engine torque (e.g. in the 2007 Ford Focus, maximum torque of 133 foot-pounds is obtained at 4,500 RPM, and maximum engine power of 136 brake horsepower (101 kW) is obtained at 6,000 RPM).

In reality, this is the number that the industry wants you to hear. However, that is only the efficiency of burning the feul to create energy. It doesn't account for the amount of feul it takes to drill, refine and transport between every stop before it reaches a gas tank, or rocket.

There really isn't much efficency difference between JP8 and gasoline, even though you probably are told so.

Just keep in mind these lasers are extremely inefficient and are somewhere around 10-18 percent depending on the temperature operating. All lasers are different, but not as different as you think. The cost of running a facility that can keep the laser cool enough to function at high efficiency would give a net (end average) efficency in the negative, or close to zero. Also keep in mind, that the average efficiency of 10-18% is very generous.

Originally posted by sbctinfantry
Just keep in mind these lasers are extremely inefficient and are somewhere around 10-18 percent depending on the temperature operating. All lasers are different, but not as different as you think. The cost of running a facility that can keep the laser cool enough to function at high efficiency would give a net (end average) efficency in the negative, or close to zero. Also keep in mind, that the average efficiency of 10-18% is very generous.

So are you saying that this claim of a 1300W laser with wall socket efficiency of 30% including cooling is false, and it's actually closer to zero?

LIMO introduces 1.3 kW diode laser with 30%efficiency

Recommend Recommend () Recommended Recommended () LIMO introduces 1.3 kW diode laser with 30%efficiency Social Media Tools Share Print Email Save Sponsored by: 08/02/2011 By David Belforte Contributing Editor,Industrial Lasers, Chief Editor, Industrial Laser Solutions LIMO Lissotschenko Mikrooptik GmbH, Dortmund, Germany, has introduced the LIMO1300-F200-SL808/9xx-EX1472, a 1.3 kW diode laser that has wall-plug efficiency of 30 percent, (including cooling). A comparison with systems in the same power class: A typical CO2 laser has an efficiency of approximately six to eight percent and a fiber laser has an efficiency of 20 to 25 percent.

Not only can you buy 30% off the shelf today, but the winner of NASA's award, Lasermotive, claims that there's a clear path to achieving efficiencies over 30%:

lasermotive.com...

Laser power beaming has only become practical within the last decade, as diode lasers have become more efficient and less expensive. Now that system efficiencies greater than 20% have been demonstrated (with a clear technical path to achieving greater than 30% in the near future), a variety of applications make economic sense.

As I said in a previous post, the current method of launching rockets with chemical propulsion is the baseline for comparison purposes that a more economical launch method will have to improve upon to be adopted. Friction is an issue during launch, but it's one that both chemical and beamed energy propulsion alike will have to overcome.

Inertia, on the other hand, would give a clear advantage to the beamed energy method of launch, because without all the extra fuel a chemical rocket needs, a beamed energy payload will have a much smaller mass launched with it, and therefore it will have a much smaller inertia to overcome than a chemical rocket, right?

I'm not arguing that the beamed energy method is highly efficient. but I also don't know what the upper limit is on efficiency..You never did say where you got this 1% figure from:

Originally posted by sbctinfantry
we all know you're only going to harness about 1% of your output unless it is a closed environment.

You managed to write a bunch of other stuff I already knew but you never explained how you arrived at 1%.

I also think you need to expand your vision from what the specific efficiency is, to what the overall launch costs are. It seems to me like that's the key issue, whether overall launch costs are more or less economical than with chemical rockets. Certainly efficiency is one factor in overall launch costs, but if NASA is considering the beamed power alternative, it's the overall economics of all related launch costs that should concern them.

Originally posted by sbctinfantry
I understand you don't study physics

I never said I don't study physics.