NSSO on Space Based Solar Power 198
apsmith writes "About a year ago some of the people at the US National Security Space Office began looking into space-based solar power (SBSP) as a technology in the near-term strategic interests of the United States. At first the participants were skeptical, and the "phase 0 study" went along with no official funding. In a rather innovative move, they organized the study as a series of internet-based (bulletin-board and email) discussions, with the wordpress site open to the public, and a closed experts-only discussion using Google Groups. Initially expecting only a dozen or so interested parties, the discussion grew to include over 170 people with past expertise and interest in the issues. The final report was released Wednesday morning; it provides an excellent broad-brush review of the status of SBSP, showing immense potential, but also a number of challenges that appear only surmountable with a strong government commitment to the project. The big question is where it goes from here — NASA? DARPA? The new ARPA-E? Or something new? I was able to attend the press conference, which included Buzz Aldrin in an announcement of a new alliance to push for implementing the recommendations of the report."
cool (Score:3, Insightful)
Ok, someone explain it to me (Score:5, Insightful)
Don't get me wrong, I'm all for finding ways to utilize space, but I don't see how this is even remotely economical, especially at our current technology levels.
Convince me.
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Re:Ok, someone explain it to me (Score:4, Informative)
So that problem's solved...leaving only the original problem of manufacturing enough defect-free tubes in enough industrially-significant quantities to make the skyhook in the first place...
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heh
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Re:Ok, someone explain it to me (Score:4, Funny)
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No weather, and a clear view (no atmosphere at all in the way).
That gives you a factor between 5 and 10 over on-the-ground systems to start with.
If you really lose 50% in transmission *and* 50% in receiving the case is harder to make - most estimates seem to have higher numbers for overall system end-to-end efficiency, but of course nobody's buit one yet.
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If you really lose 50% in transmission *and* 50% in receiving the case is harder to make - most estimates seem to have higher numbers for overall system end-to-end efficiency, but of course nobody's buit one yet.
Actually, I'm quite sure someone has built an earth bound a set of devices capable of comparable beam energy density to a proposed orbit power system. IIRC, the efficiency of the receiving antenna can be around 90%, not sure about that of the transmitter.
Personally, I'm sure an array of heat engine
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Of course, I'm more of the belief that solar power satellites will not be practical until we have off earth resources to build them from and, as such, low tech heat exchange designs are a better s
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Obviously it's no
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how do you propose we maintain them from that distance? yes, solar cells aren't this eternal source of power people think they are. expect to need to do rolling replacments every 10 years atleast, if not more under those conditions.
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Robot equipment would perform the maintenance, powered by the array itself.
...and how will the robots create a new solar panel if a panel is damaged?
Think of them as an army of advanced Roombas.
Are they able to repair themselves, and if so, where do they get spare parts?
As far as the idea is concerned, I'd not mind if they can do it cleanly. The S-G power delivery methods I'd heard of so far have been microwave-based; anyone think there'd be any impact to global warming?
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1) Over-size the array, so a few dead/damaged panels wouldn't matter.
2) Have a stock of spares. Robots cut bad panel loose, push into sun, slap spare panel into place.
3) We could ship up a stack of spares every so often.
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Interesting hard SF treatment of this in a fairly old set of novels. They were talking of communications, but the same rules apply. I recommend "The Complete Venus Equilateral" by George O. Smith.
Re:Ok, someone explain it to me (Score:4, Interesting)
And how exactly do you keep the power beam locked onto the target, when the target is on a sphere rotating once per day?
Putting them in equatorial geostationary orbits is *much* simpler. You'll lose a small amount of generating time each day (while the station is in Earth's shadow), but if you schedule as much of your maintenance as possible during this time, the effect is minimal.
And maintenance *will* be required, for the foreseeable future. Someday we may be able to build solar cells that don't need to be periodically replaced, but not today.
Furthermore, it's been noted that Earth orbit is "halfway to anywhere in the solar system" (attributed to Heinlein). So we'll need serious orbital capability to build these things, regardless of where we put them.
Point source vs. directed beam. (Score:2, Informative)
Actually, no.
Light intensity from the sun drops off at the square of the distance because the sun radiates as a point source in all directions.
If you put your collector array closer to the sun, you collect significantly more sunlight. Then you use that energy to power a laser. If
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Not a maser?
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No. An equatorial orbit only goes into Earth's shadow during two short periods a year, near the Equinoxes. Off the cuff, I think the sats will be able to enter Earth's shadow once daily for about three weeks every Equinox.
The rest of the time,
we will indeed need serious orbital capability (Score:3, Informative)
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I think it was Robert Forward who raised the possibility of putting the solar power stations on Mercury and just having them make antimatter. The antimatter is then shipped (nice, high energy density stuff that) to Earth.
There are a few engineering details yet to be worked out, of course.
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No it most certainly doesn't. The kind of power loss I am talking about is the power loss due to dispersion. The sun radiates its light in all directions, so most of it is wasted. The further you go away from it, the more it has spread out and the smaller the available density of energy is.
A perfectly collimated laser or maser (admittedly a practi
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Because you don't need batteries... (Score:5, Informative)
I'm skeptical too, but it's not quite as crazy as it sounds.
The difference between... cannot go wrong (Score:3, Interesting)
Lets build in some redundancy shall we? (Just in case.)
I think you covered the list pretty well but corrosion is also a factor that space should mitigate. Well, mostly aside from the wandering bit of space debris.
I haven't RTFA, probably won't, but I'd
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Re:Ok, someone explain it to me (Score:5, Informative)
Portability:
By using an orbital energy collection system, you can simply re-route the beam to any place on the planet within the system's FOV...done right, you can get full 4*pi sr coverage of the Earth 24/7. Design a portable ground station, and you can provide power to a disaster area that has been removed from the rest of the power grid (paraphrased directly FTA).
Extensibility:
If, once in place and a standard orbital collection platform design has been established, more power is required, simply launch the spare unit. Proper formation flying techniques (something currently at about the cutting edge of orbital design) should allow the new unit to 'hook in' to the system to boost the amount of available power. This may be in the article, I have not finished reading it yet.
The LISA mission provides a pretty good overview of how I see the entire system distributing power from the collectors to the emitters (the things that will transmit the power down to the surface), though I may be totally off base from what the authors have in mind. The LISA mission will consist of three satellites forming an equilateral triangle with leg lengths of 5 million Km shooting lasers at each other. Last time I checked, anyway.
It is currently not economical, nor is it really achievable yet. I encourage you to at least browse through the article as it does discuss some of your questions in a more cogent manner than I have.
Re:Ok, someone explain it to me (Score:5, Informative)
The second number, however is totally wrong. If you're going to talk about what "the sun provides", i.e., the theoretical 100% efficiency solar panel, then you get a figure of about 1000W/m^2 on the Earth's surface. You could say it is more like 800W/m^2 when you take cloud cover into consideration.. and then there's the fact that you only get that during daylight hours, so halve it to get 400W/m^2 but that's still a lot more than 250W/m^2. It *feels* like someone is downplaying the possible efficiency of solar panels on the Earth's surface vs the same solar panel in space in order to make their argument stronger. As you took that figure straight from the article, I'll give you the benefit of the doubt, but that's what it sounds like.
It's still a heck of a lot of difference though. You're talking nearly 3.5 advantage to putting your solar panels in space over leaving them on the ground.. but there *are* losses to transmitting the power as microwaves through the atmosphere, and there is the astronomical cost of launching anything into space.
Whenever I hear people talk about solar power satellites I'm reminded of the episode of Seinfeld where they stock the mail truck with bottles to collect the 5c deposit in the adjacent state. If you can get a free ride you might be able to make solar satellites work, but you've still gotta crunch a lot of numbers first, and no-one has done that successfully.
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Solar cells on earth aren't exposed to an "average" per unit area, you put them in the places where they work best, like high, cloudless deserts, and you steer them.
1/2 of 1000, since half the time is still night-time
And solar cells in orbit around the earth move through the earth's shadow. You can't put them into geostationary orbits (too crowded), and further out is expensive. Maybe we could build stators.
If you were able to keep the arra
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Well, it ain't gonna happen: that space is too valuable and too crowded.
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It's space, dude.
The orbit is 264,869 km around.
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http://www.google.com/search?q=geostationary+orbit+crowded [google.com]
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[p]
You put the current communication satellite transponders (rather, their replacements) aboard the powersats. You give them bigger antennae. The bigger the antenna (at either end) the better the angular resolution.
The "too crowded" comes down to angular resolution, not actual distance. They're not (much) worried about collisions but about a receiver on Earth being able to differentiate betw
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Of course.
They're not (much) worried about collisions but about a receiver on Earth being able to differentiate between adjacent satellites.
Well, duh! Next you'll tell us space is a vacuum! What more of those incredible insights do you have up your sleeve?
You put the current communication satellite transponders (rather, their replacements) aboard the powersats.
Brilliant idea! Let's put the receivers and transmitters right next to the gigawatt microwave a
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Thank you, but it's not original.
Let's put the receivers and transmitters right next to the gigawatt microwave antenna! That will surely fix all those problems!
Yep. Unless you're trying to watch satellite TV in the middle of a rectenna farm, of course -- although even there they'd likely have the transponders for that particular region mounted on a different satellite. It's not like everything on the powersat has to point in the same direction, you know, or operate at the same frequency.
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in regards to your point 2: I took that into account with the cloud cover, etc.
as for the 1kW/m^2, look in a physics book sometime.
In regards to wikipedia, when a reference is given, it's a good idea to read it.. and when one isn't given, it's a good idea to ignore or at least be extremely skeptical of the information given.
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Another advantage is that the array could be pointed directly at the sun permanently, whereas on Earth, you need to keep swiveling it.
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idunno, it just seems like a massively complex, expensive solution to something we don't have a problem with, and won't have a problem with in the forseeable future.
by all means reasearch, and if they can make it work and make economical sense, great. i'll remain skeptical until they solve th
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We don't have a problem with shrinking available land mass, increasing dependency on oil?
It's not that complex, the cost can be amortised easily enough, we do need clean energy, and you ended your sentence with a bl**dy preposition!
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Plus which, as others here have pointed out, in space solar power is something.
Re:Ok, someone explain it to me (Score:5, Insightful)
Not likely (Score:2)
TO be honest, years ago, I thought the same thing, but if you think about it, we can simply use a nuke power plant on the ground and beam the energy to a set of sats to send the power. Just make the main receiver be at geo over USA, and then from there beam it aro
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The infrastructure developed to implement this project is pretty much the infrastructure needed to leave earth and visit other places on a regular basis.
You get the Electricity, and Access to the Universe is gravy.
Here's the explanation. (Score:2)
How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency, and then receive the beamed power at (optimistically) 50% efficiency,
First: It isn't necessarily panels. Steam plants work just fine, and are much cheaper to build and lift.
Second: There's 7 times the power per square foot available up there due to lack of atmospheric attenuation and the 24/7 nature of sunlight in space, compared
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Then you transmit the power from the small panels to an space station in a geostable orbit around earth.
Then you transmit the power from the space station to a matching ground installation on the earths equator.
Then you transmit the power from there around the earth using whatever method is best.
The strengths of such a sy
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How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency, and then receive the beamed power at (optimistically) 50% efficiency, meanwhile creating the navigational hazards of the power beams and still requiring distribution from receiving stations rather than simply generating it via panels at the point of use?
Don't get me wrong, I'm all for finding ways to utilize space, but I don't see how this is even remotely economical, especially at our current technology levels.
Convince me.
The best ideas aren't solar panels in space, they're solar mirrors for heat turbines. You ever see that tower in the desert surrounded by mirrors? Up at the top they have a fluid that gets super-heated by the mirrors and it turns a turbine. Heating a fluid and letting it turn a turbine is the oldest form of power generation we have, it's just updating the heat source to solar.
So the idea is that you put something like this in space and beam the power down with microwaves. At the moment, this sort of device
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So I assume that many other more hostile nations will be able to within 50 years.
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Most solar powersat proposals don't actually suggest this (at least, not the ones I was looking at twenty years ago). The idea is to deploy sufficient systems (as automated and self-repairing/self-replicating as possible) on the Moon that the powersats are constructed from lunar materials. This avoids the costs of manufacturing them on Earth and lifting them to orbit. Some proposals just had leaving the panels on the Moon and beaming the power from
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Actually, that part is simplicity itself. All that is needed is an array of radiator fins, positioned behind the collector mirror. In the perpetual shadow behind the collector, things are going to get very cold, and any waste heat can easily be bled off there.
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That depends on what your definition of the word "cold" is
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Basically, if you're using a steam-engine type of generator to produce your power, you're tapping into the energy of a temperature differential you're creating. Using the occluded space behind the mirror as your low point increases that differential considerably. Also, even though the only mechanism a radiator fin can lose heat by is radiation, that difficulty can be surmounted by simply increasing the surface ar
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Ahh...I'm glad you returned. I have a question.
Given the potentially huge range of temperatures we're talking about here (potentially millions of degrees in the focus of the mirror, only a few degrees above absolute zero in the shadow of the mirror), what sort of material were you considering for the heat transfer? You made a reference to "steam engines", suggesting water as a possibility, but considering the temperatures involved, might not another substance prove to be more suitable
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How about mercury vapor?
http://en.wikipedia.org/wiki/Mercury_vapour_turbine [wikipedia.org]
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Yes, but it helps if you're radiating toward the 3 kelvin background temperature of most of space, and aren't surrounded by air at around 300 kelvins radiating back at you.
Beyond the Orange-Bellied Parrot (Score:3, Interesting)
I like the idea of a separate organisation dedicated to this technology, as it's clear none of the existing organisations can do it. Set it in motion, get it done before the bloat sets in. Also like the idea of the solar-electric HEO ferry -- anyone have a link to an artist's perception of it (a real one I mean)?
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Ryan Fenton
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"Why?"
"It isn't there any more"
-- "The Moon is a Harsh Mistress", Robert A. Heinlein.
Yep, lots of energy up there, and you don't have to produce it, just sort of funnel it. Large concentrating reflectors are quite easy to maintain in microgravity, just lots of metallised mylar film with supporting struts made of alfoil. Oh, and a guidance system of some sort. Some time back there were a few designs for manufacturing these as they unrolled from st
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bring in Zaph Brannigan (Score:2)
By "something new", I'm sure you mean the formation of D.O.O.P.
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I would say the same. (Score:2)
If I needed funding for my project I would say the exact same thing, especially if I had 170 other highly skilled fanboys to back up my idea..
more intense sunlight? (Score:2)
solar cells here now aren't capable of extracting more then 35% of the light that makes it to earth now, so they won't do any better in space.
the only type of solar generation that will produce more power in space due to the more intense soalr rays will be some form of mirror heating, and that present a whole bunch of other problems.
i'm also curious as to how they will keep the solar a
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The main proposed orbit is geo-stationary; these are very rarely shaded (for about 1 month of the year a satellite there gets about an hour's worth of shade every day, the rest of the year it's clear).
Inexpensive space launch is definitely one of the technical challenges. The report calls for large-scale development and deploy
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This is exactly the way they work.
Go get yourself one of those toy solar-powered cars, or a solar energy demo kit (solar cell and motor) from Radio Shack or someplace. Move the cell towards a light bulb; observe how the motor speeds up or slows down as the cell gets more or less light.
Yes, there's an upper bound. Probaby shortly before the silicon starts to melt.
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Bzzzt... wrong.
PV panels can only extract electricity at a specific bandgap energy (although I believe recent developments allow multiple bandgaps, improving efficiency). Photons below that energy (i.e. longer wavelength) are not converte
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On earth, you get ~250w/m^2, is space, you get 4-5 times as much. So, a solar cell in orbit at the same efficiency will produce 4-5 times as much power. It's not that they are more efficient, it's that they are getting more sunlight->more po
Gerard K. O'Neill (Score:2, Informative)
It is a gun, a really big gigawatt class gun. (Score:2, Insightful)
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Besides which, I think it would be probably that the economic advantage of having this power would outweigh taking it offline willy-nilly to terrorize lesser nations...we can terrorize lesser nations quite adequate
Won't happen until one world, united. (Score:3, Insightful)
We're certainly not going to rely on a very fragile orbiting setup which is a sitting duck to anyone with a decent missile/launch vehicle.
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Justin.
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Nope.
These things will be high up - in GSO, which takes it right out of the range of any ICBM based launcher. Unless you can figure out how to pack propulsion, power, guidance, and a Dangerous Payload into a five to ten pounds or so... (And no, the classic 'handful of sand' or 'paint chip' or 'styrofoam cup' won't cut it here - the interception geometry is diff
President Camacho Has a PLAN (Score:2)
He'll pick a bunch of SMART guys and they'll solve our ENGERNY problems and they'll do it all in ONE WEEK or he'll... uh... he'll uh... give them MORE TIME and MORE MONEY because its REALLY REALLY HARD to solve our ENGERNY problems! And then if they don't do it before they die then... uh... he'll pick some MORE SMARTER GUYS and let THEM solve our ENGERNY problems!
Nothing like incentives [geocities.com]!
let me get this straight (Score:2)
And the justification for this seems rather dubious, too. Capturing solar power in space has no obvious overall advantage over capturing it on the ground.
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The US has been fielding megaton-range nuclear weapons (lately they're more sub-megaton) around the world for most of the last six decades (as have a few other countries). You're worried about a few megawatt beams?
Capturing solar power in space has no obvious overall advantage over capturing it on the ground.
Follow the money (Score:2)
It's not about the watts per square meter, or the transmission feasibility or losses, skip to the final number: how many kilograms do you have to put into HIGH orbit to deliver a 1kW to the ground?
I didn't find that number, but by searching on "$", 56 pages in to a 75 page
Jimmy Carter must be laughing his ass off (Score:5, Insightful)
So, here we are today, some 27 years later, and the same proposal gets floated.
Imagine if laziness hadn't dropped the issue back then. Iran, Iraq and the whole business of 9/11 would have been less critical than they now are.
Fatal error in their assumptions? (Score:2, Insightful)
"Conflict prevention is of particular interest to securityproviding institutions such as the U.S. Department of Defense."
Hmmmm - not on recent evidence!
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forget LEO (Score:2)
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if it's geosynchronous, you still have night time to deal with, since *shock* the earth will block the sun on you.
what makes you think your power production will double out in space suddenly. solar panels are operating at their limits under the measley solar rays we get here on earth.
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You're not thinking in orbital distances - the Earth only blocks it for a few minutes, at local midnight. Most power usage is during the day, so this would have very little impact. (Needs some design - such as getting power from another sattelite half a time zone away, but not a hard problem).
Given: GEO orbit is 35,786 km up, the Earth is 6,400 km in radius, the sun is 150,000,000 km away. Set
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don't laugh and please mod me informative ;-)
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Essentially, you create an artificial sun in GEO - except it only shines in one direction and all the energy is at one microwave frequency. That makes "solar cells" much easier to design, and much more
Launch costs can be radically improved. (Score:2)
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In LEO, you lose half the benefit because half the time, the devices are in earth's shadow.
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Hitting said targets with a few hundred pounds of TNT could cause serious damage, too.
To use the example of a megawatt beam an earlier poster mentioned, hitting a target with a one megawatt beam for one second delivers about the same energy as a hand grenade (about a half-pound of TNT). Yeah, for some very few targets that kind of exotic delivery system might be of interest, but most of the time a Tomahawk or even an RPG fired fr