Apr 14, 2016 02:43
Karen Pease
Posted on: Breakthrough Initiatives
As I've mentioned elsewhere on this site, electricity storage is not reasonable. High-power li-ions are something like $10/kW. That sort of battery buffer would be a billion dollar line-item. And that's if your lasers are 100% efficient fed straight from DC, while real world lasers tend to be notoriously inefficient. And li-ions are particularly high power batteries, and supercapacitors don't help the budget situation any, so don't expect better rates by switching technologies.
As mentioned elsewhere, it's a lot simpler than that. The highest power lasers are chemical lasers (the lasing medium is "self-cooling", as hot exhaust leaves and is replaced by (relatively) cool fuel), and they also happen to produce a high quality beam with reasonably good efficiency. No electricity storage is needed - you just need to be able to store the feedstocks, and ideally regeneratively create them onsite. Also as mentioned elsewhere, look to COIL for a good example; a syngas generator fueled by any hydrocarbon can drive the whole regenerative process (electricity for the chloralkali process, hydrogen for the anthraquinone process, CO for regenerating the iodine) for 5-6 figures ($USD) per shot with material storage requirements on the rough order of several hundred tonnes per shot and material capital costs in the 7 figures range.
This issue simply goes away. Focus your efforts on the beam creation and focusing / pointing hardware, that's where the actual challenge is. The US military has been working on this for a while for missile defence - talk with them.
Apr 17, 2016 21:40
Wissam@franklab.net
Posted on: Breakthrough Initiatives
Can we use the energy coming from the lightening ?, without the uses of capacitor, it can be used as the same instant as the delivery.
Another idea could be the direct conversion between lightning and laser. Lightning can give excitation to crystals that can be directly re-emmited to laser.
Apr 18, 2016 17:22
21laceyn@my.weston.org
Posted on: Breakthrough Initiatives
Have to you considered using thermal energy to power to nanocraft, surely lots of heat could be generated from the lasers.
Apr 25, 2016 12:25
Andrew Palfreyman
Posted on: Breakthrough Initiatives
@Karen Pease:
Good, pithy detail. But where in all this do Lubin's sexy fibre amplifiers figure? They are supposed to, after all, constitute the meat of the breakthrough here.
May 27, 2016 02:14
Dream Walker
Posted on: Breakthrough Initiatives
I do not think this issue 'goes away' quite so easily. But not impossible either.
First, this will take a lot of power. Doing this on Earth or in space leads to the same source: solar. Although we are using chemical for a limited space program, any attempt to use fossil for this project, or even water, will result in severe opposition from environmentalists, justifiably imo, for I will join with them on the lines. Every sane person who has dreamed the dream of going to the stars knows they cannot do so from a ravaged world. Nuclear not sufficient or safe, solar appears acceptable but we still will have to consider the environmental aspects if it is done from Earth, as proposed. It will probably have to be on Earth at first, later we will need to proceed from space, or the Moon. Well, that said, lets do some fun physics. The easy kind, but physics it must be, just to keep us a little grounded as we dream this dream.
1) The theoretical minimum energy required to launch a probe at relativistic speeds is the relativistic kinetic energy of the probe relative to earth , which is (gamma-1) mc^2. For a small probe of practical size (1 gram chip + 1 gram light sail) launched at 0.25 c this is (counting furiously on fingers....) a lot ~ 6 TW-s . Thats 6 Terrawatt-seconds.
showing work: gamma = lorentz factor for 0.25c = 1.0328 then
0.03280 * 2 x 10^-3 Kg x 9 x 10^16 m^2/s^2 = approx 6 x10^12 joules OR ~6 TW-s
2) To deliver 6 TW-s of energy to the probe over a 100 seconds period requires power delivery of 6TW-s/100sec ,
or 60 GW. That is the power and energy that must be delivered to the lightsail over 100 seconds.
3) The solar plant in Rosamond Californa, Solar Star, (may be the largest in the world), has a reported 0.6 GW capacity. This is plainly insufficient to deliver the required power directly. The Three Gorges Dam plant in China has a whopping 22GW capacity, but still insufficient for the 60GW requirement. So that's where the energy storage/ batteries come in.
Analysis
Hypothetically, just dreaming here folks, IF we could store 10,000 seconds (2.7 hours) of a flat out capacity output of the Solar Star Plant (thus dimming all lights in Vegas for a few hours), that would give us our 6TW-s of needed energy, but in stored form. BTW, ask an engineer, this storage can present a safety concerns, not to mention exceedingly expensive unfortunate misshaps. That much energy storage is not quite as cheap and easy as we may think, for remember that not only does it have to store the energy, it has to DELIVER 6TW-s over 100 seconds at a rate of 60GW. Got those numbers? Fortunately our engineers manage to build our ridiculous ideas on a routine basis, so I'm not personally that worried. Still, a challenge I think. I'll be amused to see how they handle the battery cooling, much less the laser cooling. These numbers also assume no losses, which is an obviously ridiculous assumption, but we are just dreaming here, so no harm done.
But the real kicker is, we are going to do this anyway, power and storage tech, because we need it INDEPENDENT of Starshot. So you might say that our space probe is getting an energy piggyback on top of our world's insatiable gluttony for POWER. You might also say this project just might magically turn one of our VICEs into a bit of a VIRTUE. A cool bonus.
Good ideas and tech are still needed here. I was concerned that Elon Musk had not joined this initiative, but I just think he's a little busy right now, everyone calling him a dreaming fool and such. I don't think he is any kind of fool, his actions make perfect sence if you view then through the STARSHOT lens. Investors pah, he's a visionary.
Conclude
Please consider this basic physics as you propose ideas for the energy problem. For example, consider whether the battery you propose can, eg deliver the requisite current etc, do so reliably, and be cost effective. As you can see, this area still could use some good ideas.
Jun 07, 2016 22:05
Andrew Palfreyman
Posted on: Centauri Dreams
In rough terms:
The latest fiber amplifiers will produce output at the 1 KW level. The latest COIL lasers will produce continuous output at the 100 KW level. So for 100 GW output (for the required 100 seconds) and assuming 100% power conversion efficiency, we either need 10^8 amplifiers or 10^6 COILs. Before proceeding, we need to cost out these two items. Any takers?
Jun 16, 2016 10:30
michael.million@sky.com
Posted on: Centauri Dreams
If we built the power system in the atacama desert we could use the vast expanse to create solar panel farms and cap banks, the cold temperatures would aid the convertion factor of light to electrical energy. The altitude would also aid the beams atmospheric transmittance and cooling systems.
Jun 22, 2016 12:30
michael.million@sky.com
Posted on: Centauri Dreams
If a MHD generator is used to create the power needed there are plenty of salts in areas of the Atacama desert that can be processed for metal ions such as sodium and lithium to aid the conductivity of the exhaust improving electrical efficiency.
Jul 01, 2016 07:05
michael.million@sky.com
Posted on: Centauri Dreams
We can generate large amounts of power with these MHD generators, since the power density is proportion to the square of the magnetic flux density, B^2, superconductors could make themselves felt in the design. By using the liquid hydrogen to first cool the superconducting magnet devices then the engine chamber/nozzle and then into the rocket engine a higher conversion efficiency can be obtained.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19970020328.pdf
