Shpaget

Like water? If you vaporize it fast enough, it looks a lot like explosion. Iron evaporates at around 2860°C, which is still within the realm of believable sci-fi weapons.

That would be quite a bit of comments, so we better get started... When it comes to space, I'm in favor of any technology study and experiment. I'd really like to see humanity in space in my remaining lifetime which, by the way, is getting shorter by a frightening rate of roughly 365 days per year. Until we get a hang of fusion, nuclear fission is still the most energetic process we can control. We should use it. As for the actual proposal to restart it, I was not able to find anything about it on NASA site and the article linked by Stranded provides little detail.

Look into teflon based products for escape proofing your enclosure. https://www.amazon.com/Insect-Ant-Barrier-Improved-Version/dp/B00UJLH12A

Could be. I just don't see direct transmission from light years away as feasible, so I assumed it would use relay system.

That's the impression I got from their press material and stuff, I could be wrong, of course, but consider this: He talks about "sending hundreds and maybe thousands" of probes for each target. He also talks about 1 W lasers mounted on the probes, and I don't see how those can work over 4 light years. At those distances, a perfect diffraction limited red laser with a lens diameter of 3 m would have a minimum beam width of around 10 million kilometers. To achieve a 1 km diameter laser spot, we would need to go to x ray wavelengths (1 nm) and scale up the size of the lens to 50 m. All that is assuming a diffraction limited optics, which a fresnel lens made out of a flimsy solar sail material that is changing shape mid-flight can't realistically be. However, let's consider that they managed to do it and get a 1 km wide laser dot smack right on top of their receivers on Earth. You are now receiving a 1 W signal over 1 km2 that is competing with natural starlight and man made interference. I'll let somebody else to figure out if that sort of signal/noise ratio is usable. Relays would make more sense.

Because you need power for all the probes en route that act as relays.

If you think that we are bashing this without reason, don't. We are calling the project out on what we see as fundamental flaws that are not just one discovery away from being solved, but deeply rooted in the laws of physics. The problem with the proposed laser launch is that this system needs mind boggling acceleration for couple of reasons. 1. They need to have a steady stream of probes to maintain the relay network (or is it a relay line?), with individual probes not too far from each other due to the problems with coms over vast distances and their fundamental lack of proper parabolic dishes and strong transmitters (they want their probes to be absolutely tiny). 2. It's not possible focus lasers over very large distances, so they need to deliver all the energy before the probe gets beyond the usable focus range of the laser (we've talked about this multiple times in the many space warfare topics that popped up on these forums over the past years). Those two facts and their wish to achieve relativistic speeds directly lead to the requirement that they deliver insane amounts of energy to the probes in very short time, which leads to several problems. The acceleration of the probes needs to be very aggressive. It is questionable if they could survive it, but even if they could, the sheer amount of energy over the short period of time will result in heating beyond any hope of ever being manageable. Earlier in this thread I said 430 trillion degrees. I did not pull that number out of my derrière, I actually did some rough math, but even if I'm three orders of magnitudes wrong, it's still hopelessly beyond being in the domain of solvable. But those two issues are far from the only ones. Every time I sit on a toilet, I find a new hole in the project. So far, these are the issues mentioned in this thread that would have to be addressed in order to achieve the goal: 1. Giant freaking lasers to push the probes (giant as in orders of magnitude larger than anything else existing). 2. Power supply for those lasers (while Earth would probably have enough grid capacity to supply it, I don't see any particular country/region on Earth that could do it by itself, and sharing the load just doesn't work). 3. Probe design that can survive the launch (so far we have no material that can even remotely approach surviving the conditions during the launch). 4. Communications between the probes (such tiny probes have no chance of transmitting and receiving over distances we are talking about). 5. Power supply for probes on their way while in interstellar space (solar panels are not an option, there is no sunlight in deep space, and laser power is out of the picture since we can neither focus the laser at the distances required nor provide laser power to all the probes in the relay line at once since the ones that are closer would cast a shadow on the ones further out). Resolving all of these issues is absolutely necessary for the accomplishment of this mission, with only the number 2. and 5. being in the realm of possible, if you could convince some country to dedicate a significant chunk of their electricity production to this project continuously for couple of decades and if we could develop some ultralight solid state radioisotope power generator for the probes themselves (which raises the issue of radiation shielding for the rest of the electronics). The rest of the issues are much harder to solve.

Go to a car tuning shop. NOX is the thing they use extensively in Fast and Furious. They call it Nitrous, NOS, etc. Comes in pretty blue bottles. Medical suppliers also have it. They call it laughing gas. They probably won't sell you.

Well, Earth gets about 1 kW per m2 (1 GW/km2) from the Sun, so if you use solar panels there is no net input, but you'd need to cover much more than 1 km2 with solar panels to get to 1 GW of laser energy delivered. Solar panels are about 20% efficient, so you need 5 km2. High power lasers are around 30% efficient, so our solar panel array climbs to about 15 km2., and then there's the beam width losses. You'd probably need to have your laser beam much much wider than the target to ensure the alignment. A factor of 10 seems highly optimistic (factor of 1 000 000 seems closer, since Voyagers parabolic antenna can aim "only" at particular hemispheres on Earth, not individual antennas), but let's go with 10 anyway - the array is now 150 km2 for 1 GW of energy delivered. So you need to take all the sunlight that usually falls on 150 km2 and dump it over just 1 km2. Yeah, it could cause some serious weather issues over a couple of decades, not to mention instantly kill every flying thing that crosses the beam. Ha! When I started to write this post, I intended to write "Nah! The Earth gets 1 GW per km2 from the Sun anyway", but just ballparking the math we get some very different answers.

It's probably been about 20 years since I launched my last model rocket, but if I remember correctly, those engines had a large spike in force at the start of the burn and then a longer period of lower thrust. That may prove to be difficult to manage. I'm also not entirely sure about the consistency and repeatability of their performance.

From the article: I don't find repeating words to indicate quantity as particularly logical, intelligent or even efficient. It's easy enough to use the system when you need to indicate just two or three instances of something, but after four or five, it is entirely unusable for humans since we are barely capable of counting in such a manner. While computers would have no problem in counting, it is still entirely inefficient usage of time. It's much faster to say you need 5 000 apples, than it is to say you need apple apple apple apple apple apple apple apple apple apple apple apple... https://en.wikipedia.org/wiki/Be_Right_Back

I'm not sure the term "plasma" would still apply XD. If all that energy was delivered instantly, it would raise the temperature of the probe (very generously assuming specific heat capacity of water) to about 430 000 000 000 (yeah, that's 430 trillion). Perhaps we're looking at this the wrong way. Maybe it's not a solar/laser sail, maybe it's a fusion drive.

Nice piece of reading! I haven't had a chance to go through it thoroughly, but one thing jumped at me - on page 10 the graph shows that even with large number of elements, an array antenna can't produce a beam narrower than about 0,45 radians (~25°), which is pretty useless for long range coms. Their proposal is to use multiple probes that would form sort of a train of moving relays. The thing is, if they take a month to accelerate one probe, than the probes are 6 light days away from each other. For comparison, Voyager probes are around 17 light hours away and require a 23 W transmitter with a 3,7 meter parabolic dish. Furthermore, on the receiving end, we use 34 meter parabolic dishes. The bandwidth they can achieve is something ridiculously low. So, they would need to significantly increase the acceleration to cut down on the distance between the probes (or use multiple laser installations for simultaneous launching of several probes). Yeah, that's one thing I haven't addressed - the politics. I figured basic laws physics will be enough, but if they somehow manage to brake those, there's no way of cutting through the red tape. That would compromise the structural integrity. You need to pull some serious gees in order to accelerate fast enough so as to not get out of range of the next probe.

Interesting approach. But it does not solve the problem entirely. There is still the issue of having no antenna for receiving from the probes further out. What I mean is if the sail is "downwind" then the problem is perhaps solved for transmitting, but you still need an antenna for receiving. If the sail is lined with reflective material for transmitting, than the receiving signal can't go through the sail to reach the probe. You'd need to somehow place a receiver in front of the probe, and that would require rigid structure quite a bit in front of the probe, and the 4 gram budget is busted. Another interesting tech, but frankly I don't know enough about it, so until I read up on the subject, I can't comment. IKAROS steering concept is ingenious, but works only with significant solar flux. It also gives us a ballpark for the sail mass - 10 grams per m2 (not counting panels and spinning weights). Another problem for Starshot to overcome. You can have the solar cells as large as you want, but there is no sunshine (or starshine) in the deep space worth mentioning. A huge solar cell array producing nothing per square cm is still producing nothing, and you need a lot to transmit over vast distances with poor antennas.

I hate to liquid on their parade (again), but what exactly have they done? They glued a few small radios on third party sats in LEO and demonstrated that they can transmit and receive signals. They could have done that on Earth. They still have not demonstrated a single technology that would make their goal feasible. This demonstration is not noteworthy. Where are the solar sails and long range coms they can't do without? They talked about using the sail as a radio antenna dish. For that they need some actuators (winches) that will form the parabolic shape of the sail (since it needs to point both forwards and backwards), how are they going to do that? These actuators are also vital for their suggested steering (for which they also need, the still lacking, navigation). What kind of transmitter do they plan on putting on the probes that would be capable of transmitting over hundreds of thousands of kilometers (assuming they launch one probe every few seconds for 20 years without missing a beat) while using a crappily malformed solar sail dish. They would need some serious umpf in that tx, even with a factory made highly accurate parabolic dish. Speaking about umpf, what about the power? Solar cells of a few cm2 will not cut it. I doubt they would be sufficient even in the region of Earth orbit. Interstellar space is out of the picture entirely. All in all, to me, their campaign seems less than honest and the hype not earned.

I'd say he's serious, however, verbal gov approval means less than diddly-squat. Furthermore, it could be dangerous to go out in public with such a statement.

I did some ballpark math before posting it, so here's what I came up with: NASA used IBM 7090 for the Mercury and Gemini program, and even during the early Apollo. 7090 could do roughly 100 KFLOPS, while modern CPUs easily get into the 100 GFLOPS (so a factor of a million). I doubt there were a million of 7090s, so at the beginning of Apollo, my statement could very well be true. Sure, the later 360 is faster than 7090, but modern GPUs go into the TFLOPS territory.

Including the computers on the ground, and entirely in the realm of "possibly more than all the computers existing at that time on the entire Earth combined".

10 years, very nice! Post a picture of the habitat? Mine were most likely L. Niger, although I've never had them checked by a professional. Not very exotic, I know, but that's what lives around here and I wouldn't consider importing a non native species, or even bringing one from the seaside to mainland.

Good luck with your ant colony! I had three queens a few years back, but once the colonies reached the size where I had to think and plan their food source, I had no choice but to set them free in the garden. I concluded that when my family members asked me "Are you seriously going to raise worms in the house????" they actually meant "You're not going to keep those things in the house!"

Well, I obviously do not think Mike caused the incident, but there was a press conference a day before, with media being allowed into the clean room, so it is conceivable that whatever happened (the "incident") is somehow related to the increased number of individuals present.

The article doesn't say anything about any damage. It only says "incident".

Possibly still somewhere in the muds of tidal zones, gasping for breath.

What specific issue are you talking about? Reaction wheels are a possible source of vibration, which could conceivably induce errors in gyro (if for example, the vibration frequency is in some resonance with the gyro sampling frequency). As for why it would be more noticeable on cubesats, I'd say because cubesats are much smaller than "regular" satellites, meaning much smaller masses involved, leading to lower robustness of the system. Don't use reaction wheels. For cubesats (specifically the ones in Earth orbit, due to the Earth's magnetic field) magnetorquers are enough. They are simple, (relatively) cheap and small. All that being said, reaction wheels are not practical for cubesats, since you still need RCS to dump the momentum of the spinning wheel and that introduces a whole lot of other issues.

I finally (after months of putting it off and not even playing the game) fulfilled two sat delivery contracts, one in high Duna orbit, the other around Ike. And that is quite something for me, since my usual playground does not extend beyond Minmus. I even installed KAC for the occasion, the action which doubled the number of mods installed. I should really play this game more.