NERVA did have problems... abysmal thrust to weight ratio
Are you speaking a language other than English here? How on Earth are you reading "abysmal thrust to weight ratio" as "unreasonably long burn time"?
An abysmal thrust to weight ratio means that you can't use it as an ascent stage. Not "it takes an unreasonably long time to burn". Seriously, how could you possibly think I was saying NERVA takes too long to burn while recommending VASIMR, and saying that NERVA fits in between chemical rockets and VASIMR?
Scrap that latter point about a 200 day burn, I shouldn't be doing math at 12 at night.
They don't get a heavy but efficient propulsion system for free. They get it for the initial launch cost
You only pay that *once* - only on the intial launch. Every time after that, yes, it is free.
propellant
1) You're seriously going to pretend that I didn't just write that? 2) The propellant mass is far less than the craft mass
, and more propellant to get it back to where it might be useful again
1) It both starts and ends where it's useful (LEO). 2) The propellant cost for a system like VASIMR maneuvering between Earth orbits, or even by planets, is tiny compared to the mass of the whole propulsion system and reactor.
If your tug is heavy that would mean that it would need to be even more efficient to be economical.
Which, has been pointed out to you, it is.
Without some plausible numbers to throw into a delta-v calculator I am afraid that I will remain skeptical.
Are you really so inept that you don't know how to go to Wikipedia and look up stats on something before you whine about it and whine about how you don't have the numbers on it? Hint: it's about 5000sec ISP. Chemical rockets are less than a tenth that much. And even with chemical rockets it would be a nice deal if you didn't have to haul up your orbital-maneuvering engines each time. With something like VASIMR, it's a huge deal.
you're looking at around a 30 minute burn. Hardly anything unusual.
I'm sorry, but were you under the bizarre impression that anyone in this thread was saying that the burn time on NERVA would be too long to be useful? And if so, why?
VASIMR exists insofar as a essentially a baby size version of it. Like the VX-200, a 200kW system, capable of, hold on to your seats, a whopping 5N of thrust!
And with the 620kg full system mass, plus 170kg propellant at 5000 ISP, the system could accelerate a 1605kg payload to 3600m/s in a 20 day period. For a matching reactor, we could use RAPID-L for estimates of what the mass would be - 670kg for 200kWe (space-based reactors have been made before - the Soviets used them heavily - but they're all old and obsolete now). Hence simply strapping 10-20 of them together and the corresponding reactors as-is would accelerate a 9,35 to 18,7 tonne payload in that time period. Of course, if you engineer a larger VASIMR and a larger reactor rather than many small ones, as is the general rule, you'll get a better mass ratio.
You're going to Mars. There's no point to trying to keep your burn down to 30 minutes.
No, the space station was a relic of the Apollo era.
Here was the thinking of the time, still high on the success of the Apollo program and dreaming of an even grander future (one in which their budgets didn't get deeply slashed).
1) We'll launch Skylab. It's going to get tons of usage. 2) At the same time, we'll develop a reusable launch system - a Space Shuttle. It's going to get tons and tons of usage and so it'll be very cheap per launch even if annual programme costs are high. And we'll save money because all disposable launch vehicle programs are going to go away. 3) Why is it going to get tons of usage? At first, mainly just restocking and reboosting Skylab. But shortly thereafter, it's going to be very busy because we're going to have three other large projects going on at the time: 3a) We're going to launch a giant 50-100 man "space base" to work on learning to live long-term and produce things in space 3b) We're going to establish a permanent moon base 3c) We're going to go be prepping to send humans to Mars, and then other celestial bodies - maybe as early as 1981! 3d) Oh, and we're also going to significantly expand our planetary exploration programme. 4) All of these things are going to require tons of launches. And the Shuttle will keep them cheap so that we can actually afford them.
That was the dream. Sure did fall apart, didn't it?
Launch #1: Earth: Launch spacecraft + heavy but efficient propulsion system + propellant tank + propellant for said system to LEO LEO: Spacecraft + heavy but efficient propulsion system + propellant tank + propellant to MTO & capture to LMO LMO: Spacecraft + heavy but efficient propulsion system + propellant tank + remainder of propellant to ETO & capture to LEO LEO: Spacecraft ditches everything else (letting it burn up), reenters and lands
Launch #2+: Exactly the same as the first
--------
Scenario 2: With a tug
Launch #1: Earth: Launch spacecraft + heavy but efficient propulsion system (the tug) + propellant tank + propellant for said system to LEO LEO: Spacecraft + tug + propellant tank + propellant to MTO & capture to LMO LMO: Spacecraft + tug + propellant tank + remainder of propellant to ETO & capture to LEO LEO: Spacecraft reenters and lands but leaves the tug behind
Launch #2: Earth: Launch spacecraft + propellant tank + propellant to LEO, but NOT another heavy but efficient propulsion system LEO: Dock with tug and direct-feed it propellant; transfer to MTO & capture LMO: Spacecraft + tug + propellant tank + remainder of propellant to ETO & capture LEO: Spacecraft reenters and lands but leaves the tug behind i LEO.
Launch #3+: Exactly the same as #2
--------
See the difference? In the latter case, you don't have to keep launching the heavy but efficient propulsion system. It's as if all subsequent launches get a heavy but efficient propulsion system for free.
Note that I made sure to point out that it's heavy because, compared to its thrust, it very much is, particularly when you include the power generation hardware (nuclear + radiators or large-scale solar). But it makes up for that with how sparingly it uses propellant.
And what I presented is the worst case. Because another advantage of tugs is that, depending on the design, not every mission has to inherently include a refuel. If the tug carries a propellant tank sufficient for a number of missions, then the tug can carry out many different orbital maneuvers with different payloads, then be replenished by a large refueling/tank replacement mission all at once. This is more cost-effective than carrying up a new, smaller tank for the tug on every launch.
Furthermore, if you think that someone hasn't "thought the concept through", it's not the GP who came up with this concept; it's a very popular, mainstream concept in the space industry, and will probably be built sooner or later.
VASIMR can provide more than sufficient thrust for a quick Mars journey, so long as you have a good-sized power source to pair to it.
There's no point to a rocket that exhausts its fuel in a few minutes or even hours when you're talking about a journey that even on a fast route will take many weeks to complete.
Part of NASA's problem is it just has too much infrastructure that it really needs to get rid of that would be way too painful for a government-run agency to just close. So it has to keep all of those people and facilities working on something. They make the goals to suit what they possess rather than the other way around. Sometimes that develops useful things. Sometimes it's just absurdly expensive busywork.
Changing the culture is going to require a combination of a White House strategy, a NASA administration, and a sympathetic congress promoting a "reorientation" of NASA. They need to sell off facilities, even if it comes at a loss, and try to route staff stuck on dead-end projects into new projects that are actually meaningful. NASA needs to stay out of the rocket industry and work on the less spectacular - but more meaningful - engineering behind the scenes required for real long-term habitation outside of Earth. Because there's a lot of it to do - decades and decades.
(Here's the things that really drive me crazy...: "The NASA people would say, ‘Come on Lori, you’ve got to talk to Elon because we got out of low-Earth orbit. We’re giving him that, but you’ve got to get him out of long-term, deep space, because that’s ours". This isn't a freaking competition people.... if someone else wants to spend their money to make hardware that is achieving a goal that you have set for yourselves then your response should be, "YEAY! How can we help?")
I can't wait to see the development budget on the world's first "no maintenance extraterrestrial stripmining robot fleet". Given that probes like Curiosity that slowly roll around making observations cost billions of USD.
And the budget for the prep missions that would be required to gather the data needed in the development of such robots.
Also: don't get your hopes up for Mars farms on early missions. Seriously. Farms that provide relevant food outputs to keep people alive are big even on Earth. Light is much scarcer on Mars, even when dust storms aren't blotting it out for weeks at a time. Anything "big" costs obscene amounts of money when you're talking about Mars. You can reduce the cost somewhat (although hardly as much as you'd want) by going with reduced-pressure greenhouses; plants can grow, with difficulty, at significantly lower pressures than humans can survive. But then you have to do all tending and harvesting while bungling around in a pressure suit, which hardly sounds like an efficient use of calories. You could instead credit a "large nuclear powered robot gardening fleet" to doing the harvesting for you... but wait until you see the price tag on that one. Also, wait until you see the amount of power it takes to supplemental-light and heat greenhouses sufficient to feed a colony. And the budget it would take to develop and deploy solar concentrators / nuclear reactors + lights to prove that.
Lets keep our expectations realistic. The first mission to Mars is not going to be growing crops and smelting steel out of regolith. Their water and fuel production rates are going to be the bare minimum trickle required to meet their needs and fuel their return vehicles. And even that won't be easy. We've been struggling for decades to find the budget for even a mission like that.
Don't get me wrong, nuclear does have some interesting avenues open to it. I just don't see nuclear thermal as among them.
I'm actually a big fan of fission fragment propulsion; I think that's a rather clever concept. It's about as high specific impulse as one could possibly get out of fission, and much higher than that of most fusion concepts, the vast majority of which we can't build today. In fact, I can't recall any fusion concept that beats it, except for fusion-driven photonic propulsion. Fission fragment concepts proposed thusfar provide thrust levels not that much less than VASIMR, but ISPs of over 100k sec.
Further in the future, I've pondered the concept of using Jupiter as an antimatter factory. Jupiter corrals the highest density of high-energy particles in the solar system into broad belts. They're of course still far too low energies and densities for antimatter production, but with a large enough magnetic pinch feeding it, I wouldn't be surprised if a realistic system could be designed to produce high flux beams in the dozens to hundreds of GeV energies required over a good-sized target (note: I haven't attempted to simulate this!). If you can get nature to provide your ion beam for you - a large/intense enough of one - then the concept of using antimatter as fuel could potentially become plausible. Here on Earth, the energy required to generate such beams renders antimatter implausible for direct spacecraft propulsion.
Don't get your hopes up for gardens;) Don't get me wrong, the first mission will surely involve plants. But they'll be more along the lines of something with a cutsie acronym like MAPLE (MArs PLant Experiment) or the like. It'll be a little self-contained box the size of a beach ball with its own self-contained grow environment that raises enough lettuce for a salad or two and the occasional sprig of basil. And NASA will make sure to get about 50 press releases out of it.
That's actually part of the reason for seeking faster transit times via better engines - to minimize the radiation dose to the crew, so that their health isn't compromised upon arrival. It's sort of an acceptance that we don't really have a good solution for it, and it might well be cheaper just to develop and deploy a better propulsion system (that benefits us elsewhere as well) than to launch a massive amount of shielding.
Or, for current tech (we don't have any nuclear reactors designed for use in space at the moment), solar-electric tugs. But indeed, tugs are an idea that's long overdue. High ISP propulsion systems have tiny thrust to dry mass ratios, so launching all of that dry mass every time is a major waste when you could just be launching the propellant.
In the context of Mars, one looks at cyclers - craft designed to continually transfer between Earth and another body while hauling payloads, only needing periodic propellant refueling. And a Mars-designed cycler should also be able to supply a colony on Venus as well - the ISP from LEO to a transfer orbit is almost identical for both, and otherwise a Venus cycler has an easier job (shorter trips, more abundant solar power, etc).
There's also the issue of reusable landers on the other side. Again, it makes no sense to have to haul a new lander each time, particularly when you're planning to use local propellant production. On Mars, single stage landers are not that challenging - the gravity and atmospheric pressure are quite low. An SSTO is harder for Venus, but doable (the other option is sending a drop tanks from Earth for each launch). Compared to Earth, Venus has 90% of the gravity, a higher starting launch altitude, a lower starting launch pressure (simplifying engine design), lower reentry shielding requirements, no need for the structural strength to stand on a solid surface (only to hang), and lower insulation requirements for supercooled propellants (Venus air doesn't liquefy and run off, drawing out heat like Earth air does; it just freezes in place, like water vapor does, forming an insulative layer). Both Venus and Mars have lower launch velocities than Earth at the equator (particularly Venus, but also Mars); however, overall they're easier targets for SSTOs than Earth (particularly Mars).
To be fair, NERVA did have problems. Good ISP (~850 sec), but abysmal thrust to weight ratio - depending on what numbers you look at, somewhere between 0,2:1 and 0,5:1 wet, 3-4 dry.
That really puts it as somewhere in-between chemical rockets and VASIMR, which has an even lower thrust to weight ratio but even higher ISP. The thing is... it's sort of an awkward middle ground. If you're going to Mars, you don't need your thrust to be delivered all that quickly. And VASIMR already exists. So unless you can dramatically improve on the NERVA concept, one has to wonder, what's the point?
(Totally ignoring the inevitable public opposition here)
Still not new. I was working for Rockwell-Collins back in 2000 and our department went to a lecture from a guy talking about Chinese work on radar. One of the concepts that they were apparently working on was broadcasting broad-spectrum noise and looking for statistical correlations in the return.
Wrong. Even the first one to land successfully, Venera 7, lasted for 23 minutes. And that was after a long descent. Venera 8 lasted 50 minutes. Venera 9, 53. Venera 10, 65. Venera 11, 95. Venera 12, 110 minutes. And these were rather cheap Soviet probes, hardly a dedicated system designed for long-term surface operations. Yet one doesn't need to stay on the surface for a long time if you have a local habitat. You descent, gather information and samples, return to altitude (actually to higher than when you left, to catch up), dock and deliver, then return to the surface. Each hop lets you explore a different part of the planet - something Mars rover operators could only dream of. Such a Venus program could sample and analyze the entire planet's surface.
What is boring about an atmosphere of a planet that contains iron in it? Venus's atmosphere is fascinating - it contains vastly more material diversity than Earth's, stratified into its different layers. Near the surface the harsh conditions extract metals as gaseous chlorides and fluorides, out of surfaces that appear as if molten rock - probably things like kimberlites and carbonatites - flowed like rivers. Most of the atmosphere is dynamically stable, like Earth's stratosphere, although the middle cloud - the habitable layer - has some degree of convection, like a mild version of Earth's troposphere. Near the poles there's a crazy freaky looking storm, although we have no clue at this point at what layers, if any, it'd be hazardous in and at what layers, if any, it'd be safe in. Lightning on Venus appears to be at least as common on Earth, but it's... weird. We're having trouble interpreting the data we've gotten so far, which has led to weird theories such as lightning bolts hundreds of kilometers long (probably not) to electrostatic "traps" that echo static from lightning around the planet, to layers of the Hadesphere that deliver a static shock to objects descending through them. But lightning flashes have never been observed, so it may not exist in the upper layers at all. Venus has crazy stratified winds that rotate much faster than the planet, leading to a "day" that's nearly an Earth week near the equator but only two days at 70 degrees latitude and even shorter the further toward the poles you go. The velocities are highly stratified by altitude, leading to great potential for wind energy. The atmosphere holds tons of mysteries still, like whether the "night glow" is real and if so what it is, or what it is that makes up the "mystery UV absorber" that soaks up most of the UV light in Venus's upper atmosphere (a benefit Martians could only wish for)
Not boring at all. It's one of if not the most interesting atmospheres in the solar system.
It would be possible to have a habitat descend below the lower cloud deck (indeed, the lower cloud layer appears to be somewhat uneven in thickness and may have gaps altogether) for short periods, wherein one could see the ground with their own eyes. Yet at the polar vortex the sky clears up at such a low height that a high colony could potentially see the stars. The ground is accessible by probes, and looks to be quite a mineral wealth - but the real life is in the clouds. Not only to fuel industry, but basically you're living in a floating Garden of Eden over Hell: vast amounts of space to live in (unlike a pressure vessel on Mars, which due to how heavy pressure vessels are, will always be very space limited), always temperate, tons of sunlight to fuel the growth of whatever tropical plants one desires, and easy buoyancy to lift a lot of them. Space on a scale that a popular recreational activity might be indoor skydiving onto the safety netting. You can even step outside and touch the atmosphere with your bare skin (just not for too long). Feel an alien wind.
For impersonal reasons, a colony there is not just appealing from the perspective of a no-mining-needed industrial basis, but also from a science basis; there's far more scientific reason to have humans on Venus than on Mars. And not just because we know far less about our "evil twin" than we do about Mars. On Mars, it makes basically no difference if you leave a robotic probe sitting around recharging its batteries in the weak sunlight while it awaits commands. You can't do that on Venus's surface. You have limited time on the surface with each dive before you have to rise to cool down and recharge; latency really does matter.
See my comment further down. I'd pick around 70 degrees latitude, 55,5km altitude during the daytime, 52km at night. A correction: the surface is not awash in sulfuric acid. Sulfuric acid cannot exist anywhere close to those temperatures at Venus pressures; it starts to fade out in the lower cloud (which seems more likely to be dominated by phosphoric acid) and completely gone by the lower haze. Also note that in none of the cloud decks are you "awash" in acid. They're acid mists, a few milligrams per cubic meter - similar to volcanic acid fogs or unscrubbed smogs on Earth. You could stand out in it (for a few hours, at least) if you had a full face mask on but otherwise no special protection (long term skin exposure to those levels however would cause dermatitis).
On the other hand, the mists are a huge *resource*. They're about 25% water to begin with, and H2SO4 heated breaks down first into H2O + SO3, and then with further heating the SO3 breaks down into SO2 and O2. So right there you have your two most important resources for a colony. There's a wide range of chemicals mixed into the mists, most of which are critical to establishing a local plastics industry, and are relatively easy to isolate and separate - the same heating system allows for fractional distillation, with an optional fractional crystallization step afterwards. So your habitat is PTFE with a ripstop (I'm preferential to UHMWPE, since it's one of the easier polymers to produce locally), and you have everything in your mists (and the air, for the Fischer-Tropsch/Sabatier hydrocarbon synthesis) to produce every step of the way - even the HF. After passing the hydrocarbons through an alkalai/rare earth catalyst bed at 20-60 bar and 500-900K, or a SAPO catalyst bed at 1-3 bar, 850K, you can recover alkenes; ethylene of course goes through a Zeigler-Natta catalyst at 1-3 bar / 300-320K to make UHMWPE, while the propylene goes into the SOHIO process (0,5-2 bar, 700-800k), mainly to recover the acrylonitrile fraction, which is polymerized (low pressure and temperature) and wet spun to make PAN, which is then oxidized and then carbonized to produce carbon fiber. Your other hydrocarbon fractions are turned back into syngas and fed back into your hydrocarbon synthesis. As for the PTFE side of the equation, there's significant HCl in the mists, which the Deacon process converts to Cl2,which is then used for the chlorination of methane to make chloroform (about 700K). This then is fluorinated at high temperatures and low pressures, fed into a neutralizaton stage (which involves sodium hydroxide recycled by the chloralkali process), then polymerized to PTFE. For your plants your nitrates are of course made nitric acid by the Haber and then Ostwald process; all local wastes are incinerated and the ash neutralized with the nitric acid, so your cations are recovered. Additional sulfates, phosphates, etc are abundantly available locally. Even iron is likely available in limited quantities; one of the Venera probes detected iron during its descent, and ferric chloride is considered a likely component of the cloud deck (possibly as a significant part of the mystery UV absorber). This would be left as a precipitate in the initial mist distillation stage.
I'm oversimplifying to a great degree here, mind you, but that's the basic layout for a starter industrial base on a Venus colony. It's amazing how much is available in the cloud decks, sucked right in through your motors (that you need to resist the meridional drift) and quite hygroscopic, so readily absorbed if you duct the thrust across absorption beds. You can also get even more if you're willing to spend the power (and ship the mass) for a cooling system to cool the interior air to below ambient, and then collect the condensation that runs down the habitat. Oh yeah, I probably forgot to mention that normal Earth air is a lifting gas on Venus... you live *inside* the envelope. More specifically, near the top, as you need the ballonets near the bottom for stability, you reduce the
In case you haven't noticed, Mars drains the lion's share of the exploration dollars these days.
It's kind of weird, really - we're far more obsessed with Mars now that we know it's a perchlorate-laden organics-destroying corrosive silicosis-risk hexavalent-chromium-laden dustscape than we were back when for all we knew there was life just sitting there on the surface. It's totally disproportionate to what we know of our solar system. If the goal was to find life, we'd be prioritizing Enceladus, whose oceans (containing a known potential energy source, H2) gush out into space for easy pickup by spacecraft. If the goal was to settle, we'd be priorizing Venus, which offers earthlike gravity, earthlike pressures, earthlike temperatures, requires no radiation protection, provides vast amounts of living space (pressure vessels = small, cramped per unit mass), vast amounts (well surpassing Earth) of energy (solar, wind), and for which all of the components of a plastics industry (and probably small steel industry as well, based on the evidence for FeCl3/FeCl2) get blown through your engines in a highly hygroscopic form from which water and oxygen can be recovered by mere heating and filtering. Meanwhile, you're sitting over a potential treasure trove where high heat, pressure and acids have been extracting minerals for rocks and concentrating them for billions of years, a region with pressures only 8% that of the deepest oceans on Earth and temperatures that can be - and have been, on 1960s Soviet tech - withstood by simple thermal inertia - and from which dredged materials can be hauled up by phase change balloon (rigid metal, contracting metal, Zylon, possibly others).
I'm all for that. Venus is a far more human-friendly target for colonization, and as for simple basic science, we know vastly less about Venus than we do Mars.
It caught them by surprise. Moon dust turned out to be a lot more problematic of a substance than was initially expected. In some ways, not in others. There were lots of worries about moon dust before NASA got there... most famously that the dust layer may be so deep and loose that it would just swallow up a spacecraft. Another hypothesis that wasn't retired until after the moon landings was that, due to its reduced nature, that it might be pyrophorric in contact with air - either immediately, or with a delay. The first Apollo mission had to conduct tests to make sure that they wouldn't destroy their spacecraft in a moon dust-triggered inferno;)
Strangely, it smells like spent gunpowder. The reason for this is unknown; it's certainly chemically nothing like spent gunpowder. A leading theory is that the smell is again due to the reduced nature of lunar dust, something you don't find on Earth - that because there's lots of oxidation potential to it, it tends to bond well with nasal receptors.
And beyond that, you don't need soil to grow plants. Hydroponics / aeroponics are pretty much perfectly suited for Mars agriculture - minimizing the water and nutrient loads needed.
The soil simulants were provided by NASA, with the moon soil actually coming from a desert in Arizona, and the Mars soil coming from a Hawaiian volcano
Huh? What kind of lousy "simulants" are those? Is Hawaiian volcano soil rich in perchlorates? Martian regolith is oxidizing enough that if you were playing around in it with your bare skin you'd get burns; it's similar to handling undiluted lye or bleach, highly destructive to organic matter.
It's also very corrosive just from abrasion, although lunar regolith is worse. Trivia for people here: how many vacuum-sealed samples of lunar regolith do you think we have left over from the Apollo days? Answer: none. The regolith abraded the seals over time, creating pinpoint leaks; every last sample is now partially oxidized by Earth air.
Additionally, both are believed to be very hazardous in terms of silicosis risk, akin to breathing what comes off of a rock crusher (Mars's is finer, but both are in the hazardous range). Martian regolith has some other nasty chemical surprises though (beyond the perchlorates)... among the contaminants that have been identified is what appears to be significant amounts of hexavalent chromium. That's the type of chromium almost never found in nature on Earth (because we live in an oxidizing environment) that's extremely toxic to people (think Erin Brockovich).
This isn't just Earth soil; it's a totally different beast.
Anyway, I'm not that big of a Mars fan... I'll take a colony on Venus any day over one on Mars.;)
Also, my other thought on this topic is, air superiority and air to ground attacks are all good, but that's only half of the picture, you still have to have some sort of ground capabilities to take and hold ground. When will that go robotic?
It's obviously a lot further into the future. One envisions, rather than raining bombs down on a city, one rains down small (as small as you can) armed "rovers" with rapid reaction times to gunfire (issuing counterfire / seeking cover) and constant close communications with air support and reinforcements. So if someone does attack or take one out, they're quickly swarmed by reinforcements. And obviously if the rovers visually identify weapons they can engage targets - under human control if unjammed, autonomously if jammed. Most of the time you'd want them sitting still and conserving power (they'd either need to be able to access refueling drops on their own, be passively powered, or self-destruct when their energy supplies run out), but you'd ideally want a platform mobile enough that it could move between areas, through buildings, etc if needed, and ideally at a good speed. In civilian areas you'd want them to be very obvious and actively warn people away from them in their local language.
Counter-tactics to such weapons would obviously be tactics that keep as far away from it as possible (so that you're not at the site when reinforcements arrive) and offer no reasonable reaction time to the attack, such as IEDs. Counters to that, in turn, are more eyes looking for suspicious activity and better sensors.
Indeed. Release a drone from altitude and you don't technically even need to give it active propulsion, just active flight surfaces to control its glide. That said, with a glider or weak-powered craft, you are going to be fairly subject to winds. Then again, that only matters for some types of applications - it would be a problem for using them to conduct a ground attack or surveilance, but if you're using the drones as sort of a smart aerial "screen" against incoming missiles, maybe not.
Seems to me that the most logical approach for hitting ground targets is paired active/passive control. You make each element smart enough to carry out the mission on its own reasonably well, but have a human controlling the elements / swarms for as long as they can. So they can't stop the attack or re-route it by jamming - if they jam, it goes into auto attack mode. Which if anything would make them more likely to attack, because then you no longer have a human worrying, "is that actually a military target or could I possibly be mistaking something civilian?" - instead, a fraction of the swarm goes after the jammer while the others seek other targets in the area. You deincentivize jamming, in favor of hiding.
The two keys to cost are mass production and size. They really could get very low unit prices here. And shaped charges aren't that heavy at all. A few kilograms can take out a tank. Far less for lightly-armoured or unarmoured targets. And the smarter the attacking element, the more effective it can be with its charge - focusing on weak points or hitting areas that have already been damaged. You already see the move in this direction with modern anti-tank weaponry.
On the downside, you face risks of ending up releasing "unexploded bomblets". You really need to get the dud rate down to essentially zero for that to be acceptable in modern warfare.
You must have personal presence at the battlefield, to gather information, not hit friendlies, perhaps captive, or because your enemy has in fact surprised you and carried the fight to your doorstep.
Hence the other key aspect of the F-35, the sensor suite.
despite costing several times as much
On the other hand, the F-35 is designed to reduce ongoing costs - both maintenance (though that remains to be proven), and basing / supply line costs.
Slashdot Mirror
Are you speaking a language other than English here? How on Earth are you reading "abysmal thrust to weight ratio" as "unreasonably long burn time"?
An abysmal thrust to weight ratio means that you can't use it as an ascent stage. Not "it takes an unreasonably long time to burn". Seriously, how could you possibly think I was saying NERVA takes too long to burn while recommending VASIMR, and saying that NERVA fits in between chemical rockets and VASIMR?
No, you shouldn't.
You only pay that *once* - only on the intial launch. Every time after that, yes, it is free.
1) You're seriously going to pretend that I didn't just write that?
2) The propellant mass is far less than the craft mass
1) It both starts and ends where it's useful (LEO).
2) The propellant cost for a system like VASIMR maneuvering between Earth orbits, or even by planets, is tiny compared to the mass of the whole propulsion system and reactor.
Which, has been pointed out to you, it is.
Are you really so inept that you don't know how to go to Wikipedia and look up stats on something before you whine about it and whine about how you don't have the numbers on it? Hint: it's about 5000sec ISP. Chemical rockets are less than a tenth that much. And even with chemical rockets it would be a nice deal if you didn't have to haul up your orbital-maneuvering engines each time. With something like VASIMR, it's a huge deal.
I'm sorry, but were you under the bizarre impression that anyone in this thread was saying that the burn time on NERVA would be too long to be useful? And if so, why?
And with the 620kg full system mass, plus 170kg propellant at 5000 ISP, the system could accelerate a 1605kg payload to 3600m/s in a 20 day period. For a matching reactor, we could use RAPID-L for estimates of what the mass would be - 670kg for 200kWe (space-based reactors have been made before - the Soviets used them heavily - but they're all old and obsolete now). Hence simply strapping 10-20 of them together and the corresponding reactors as-is would accelerate a 9,35 to 18,7 tonne payload in that time period. Of course, if you engineer a larger VASIMR and a larger reactor rather than many small ones, as is the general rule, you'll get a better mass ratio.
You're going to Mars. There's no point to trying to keep your burn down to 30 minutes.
No, the space station was a relic of the Apollo era.
Here was the thinking of the time, still high on the success of the Apollo program and dreaming of an even grander future (one in which their budgets didn't get deeply slashed).
1) We'll launch Skylab. It's going to get tons of usage.
2) At the same time, we'll develop a reusable launch system - a Space Shuttle. It's going to get tons and tons of usage and so it'll be very cheap per launch even if annual programme costs are high. And we'll save money because all disposable launch vehicle programs are going to go away.
3) Why is it going to get tons of usage? At first, mainly just restocking and reboosting Skylab. But shortly thereafter, it's going to be very busy because we're going to have three other large projects going on at the time:
3a) We're going to launch a giant 50-100 man "space base" to work on learning to live long-term and produce things in space
3b) We're going to establish a permanent moon base
3c) We're going to go be prepping to send humans to Mars, and then other celestial bodies - maybe as early as 1981!
3d) Oh, and we're also going to significantly expand our planetary exploration programme.
4) All of these things are going to require tons of launches. And the Shuttle will keep them cheap so that we can actually afford them.
That was the dream. Sure did fall apart, didn't it?
Here's the part you're missing.
--------
Scenario 1: No tug.
Launch #1:
Earth: Launch spacecraft + heavy but efficient propulsion system + propellant tank + propellant for said system to LEO
LEO: Spacecraft + heavy but efficient propulsion system + propellant tank + propellant to MTO & capture to LMO
LMO: Spacecraft + heavy but efficient propulsion system + propellant tank + remainder of propellant to ETO & capture to LEO
LEO: Spacecraft ditches everything else (letting it burn up), reenters and lands
Launch #2+:
Exactly the same as the first
--------
Scenario 2: With a tug
Launch #1:
Earth: Launch spacecraft + heavy but efficient propulsion system (the tug) + propellant tank + propellant for said system to LEO
LEO: Spacecraft + tug + propellant tank + propellant to MTO & capture to LMO
LMO: Spacecraft + tug + propellant tank + remainder of propellant to ETO & capture to LEO
LEO: Spacecraft reenters and lands but leaves the tug behind
Launch #2:
Earth: Launch spacecraft + propellant tank + propellant to LEO, but NOT another heavy but efficient propulsion system
LEO: Dock with tug and direct-feed it propellant; transfer to MTO & capture
LMO: Spacecraft + tug + propellant tank + remainder of propellant to ETO & capture
LEO: Spacecraft reenters and lands but leaves the tug behind i LEO.
Launch #3+:
Exactly the same as #2
--------
See the difference? In the latter case, you don't have to keep launching the heavy but efficient propulsion system. It's as if all subsequent launches get a heavy but efficient propulsion system for free.
Note that I made sure to point out that it's heavy because, compared to its thrust, it very much is, particularly when you include the power generation hardware (nuclear + radiators or large-scale solar). But it makes up for that with how sparingly it uses propellant.
And what I presented is the worst case. Because another advantage of tugs is that, depending on the design, not every mission has to inherently include a refuel. If the tug carries a propellant tank sufficient for a number of missions, then the tug can carry out many different orbital maneuvers with different payloads, then be replenished by a large refueling/tank replacement mission all at once. This is more cost-effective than carrying up a new, smaller tank for the tug on every launch.
Furthermore, if you think that someone hasn't "thought the concept through", it's not the GP who came up with this concept; it's a very popular, mainstream concept in the space industry, and will probably be built sooner or later.
VASIMR can provide more than sufficient thrust for a quick Mars journey, so long as you have a good-sized power source to pair to it.
There's no point to a rocket that exhausts its fuel in a few minutes or even hours when you're talking about a journey that even on a fast route will take many weeks to complete.
Couldn't agree with you more. :)
Part of NASA's problem is it just has too much infrastructure that it really needs to get rid of that would be way too painful for a government-run agency to just close. So it has to keep all of those people and facilities working on something. They make the goals to suit what they possess rather than the other way around. Sometimes that develops useful things. Sometimes it's just absurdly expensive busywork.
Changing the culture is going to require a combination of a White House strategy, a NASA administration, and a sympathetic congress promoting a "reorientation" of NASA. They need to sell off facilities, even if it comes at a loss, and try to route staff stuck on dead-end projects into new projects that are actually meaningful. NASA needs to stay out of the rocket industry and work on the less spectacular - but more meaningful - engineering behind the scenes required for real long-term habitation outside of Earth. Because there's a lot of it to do - decades and decades.
(Here's the things that really drive me crazy...: "The NASA people would say, ‘Come on Lori, you’ve got to talk to Elon because we got out of low-Earth orbit. We’re giving him that, but you’ve got to get him out of long-term, deep space, because that’s ours". This isn't a freaking competition people.... if someone else wants to spend their money to make hardware that is achieving a goal that you have set for yourselves then your response should be, "YEAY! How can we help?")
I can't wait to see the development budget on the world's first "no maintenance extraterrestrial stripmining robot fleet". Given that probes like Curiosity that slowly roll around making observations cost billions of USD.
And the budget for the prep missions that would be required to gather the data needed in the development of such robots.
Also: don't get your hopes up for Mars farms on early missions. Seriously. Farms that provide relevant food outputs to keep people alive are big even on Earth. Light is much scarcer on Mars, even when dust storms aren't blotting it out for weeks at a time. Anything "big" costs obscene amounts of money when you're talking about Mars. You can reduce the cost somewhat (although hardly as much as you'd want) by going with reduced-pressure greenhouses; plants can grow, with difficulty, at significantly lower pressures than humans can survive. But then you have to do all tending and harvesting while bungling around in a pressure suit, which hardly sounds like an efficient use of calories. You could instead credit a "large nuclear powered robot gardening fleet" to doing the harvesting for you... but wait until you see the price tag on that one. Also, wait until you see the amount of power it takes to supplemental-light and heat greenhouses sufficient to feed a colony. And the budget it would take to develop and deploy solar concentrators / nuclear reactors + lights to prove that.
Lets keep our expectations realistic. The first mission to Mars is not going to be growing crops and smelting steel out of regolith. Their water and fuel production rates are going to be the bare minimum trickle required to meet their needs and fuel their return vehicles. And even that won't be easy. We've been struggling for decades to find the budget for even a mission like that.
Don't get me wrong, nuclear does have some interesting avenues open to it. I just don't see nuclear thermal as among them.
I'm actually a big fan of fission fragment propulsion; I think that's a rather clever concept. It's about as high specific impulse as one could possibly get out of fission, and much higher than that of most fusion concepts, the vast majority of which we can't build today. In fact, I can't recall any fusion concept that beats it, except for fusion-driven photonic propulsion. Fission fragment concepts proposed thusfar provide thrust levels not that much less than VASIMR, but ISPs of over 100k sec.
Further in the future, I've pondered the concept of using Jupiter as an antimatter factory. Jupiter corrals the highest density of high-energy particles in the solar system into broad belts. They're of course still far too low energies and densities for antimatter production, but with a large enough magnetic pinch feeding it, I wouldn't be surprised if a realistic system could be designed to produce high flux beams in the dozens to hundreds of GeV energies required over a good-sized target (note: I haven't attempted to simulate this!). If you can get nature to provide your ion beam for you - a large/intense enough of one - then the concept of using antimatter as fuel could potentially become plausible. Here on Earth, the energy required to generate such beams renders antimatter implausible for direct spacecraft propulsion.
Don't get your hopes up for gardens ;) Don't get me wrong, the first mission will surely involve plants. But they'll be more along the lines of something with a cutsie acronym like MAPLE (MArs PLant Experiment) or the like. It'll be a little self-contained box the size of a beach ball with its own self-contained grow environment that raises enough lettuce for a salad or two and the occasional sprig of basil. And NASA will make sure to get about 50 press releases out of it.
That's actually part of the reason for seeking faster transit times via better engines - to minimize the radiation dose to the crew, so that their health isn't compromised upon arrival. It's sort of an acceptance that we don't really have a good solution for it, and it might well be cheaper just to develop and deploy a better propulsion system (that benefits us elsewhere as well) than to launch a massive amount of shielding.
Or, for current tech (we don't have any nuclear reactors designed for use in space at the moment), solar-electric tugs. But indeed, tugs are an idea that's long overdue. High ISP propulsion systems have tiny thrust to dry mass ratios, so launching all of that dry mass every time is a major waste when you could just be launching the propellant.
In the context of Mars, one looks at cyclers - craft designed to continually transfer between Earth and another body while hauling payloads, only needing periodic propellant refueling. And a Mars-designed cycler should also be able to supply a colony on Venus as well - the ISP from LEO to a transfer orbit is almost identical for both, and otherwise a Venus cycler has an easier job (shorter trips, more abundant solar power, etc).
There's also the issue of reusable landers on the other side. Again, it makes no sense to have to haul a new lander each time, particularly when you're planning to use local propellant production. On Mars, single stage landers are not that challenging - the gravity and atmospheric pressure are quite low. An SSTO is harder for Venus, but doable (the other option is sending a drop tanks from Earth for each launch). Compared to Earth, Venus has 90% of the gravity, a higher starting launch altitude, a lower starting launch pressure (simplifying engine design), lower reentry shielding requirements, no need for the structural strength to stand on a solid surface (only to hang), and lower insulation requirements for supercooled propellants (Venus air doesn't liquefy and run off, drawing out heat like Earth air does; it just freezes in place, like water vapor does, forming an insulative layer). Both Venus and Mars have lower launch velocities than Earth at the equator (particularly Venus, but also Mars); however, overall they're easier targets for SSTOs than Earth (particularly Mars).
To be fair, NERVA did have problems. Good ISP (~850 sec), but abysmal thrust to weight ratio - depending on what numbers you look at, somewhere between 0,2:1 and 0,5:1 wet, 3-4 dry.
That really puts it as somewhere in-between chemical rockets and VASIMR, which has an even lower thrust to weight ratio but even higher ISP. The thing is... it's sort of an awkward middle ground. If you're going to Mars, you don't need your thrust to be delivered all that quickly. And VASIMR already exists. So unless you can dramatically improve on the NERVA concept, one has to wonder, what's the point?
(Totally ignoring the inevitable public opposition here)
Still not new. I was working for Rockwell-Collins back in 2000 and our department went to a lecture from a guy talking about Chinese work on radar. One of the concepts that they were apparently working on was broadcasting broad-spectrum noise and looking for statistical correlations in the return.
Wrong. Even the first one to land successfully, Venera 7, lasted for 23 minutes. And that was after a long descent. Venera 8 lasted 50 minutes. Venera 9, 53. Venera 10, 65. Venera 11, 95. Venera 12, 110 minutes. And these were rather cheap Soviet probes, hardly a dedicated system designed for long-term surface operations. Yet one doesn't need to stay on the surface for a long time if you have a local habitat. You descent, gather information and samples, return to altitude (actually to higher than when you left, to catch up), dock and deliver, then return to the surface. Each hop lets you explore a different part of the planet - something Mars rover operators could only dream of. Such a Venus program could sample and analyze the entire planet's surface.
What is boring about an atmosphere of a planet that contains iron in it? Venus's atmosphere is fascinating - it contains vastly more material diversity than Earth's, stratified into its different layers. Near the surface the harsh conditions extract metals as gaseous chlorides and fluorides, out of surfaces that appear as if molten rock - probably things like kimberlites and carbonatites - flowed like rivers. Most of the atmosphere is dynamically stable, like Earth's stratosphere, although the middle cloud - the habitable layer - has some degree of convection, like a mild version of Earth's troposphere. Near the poles there's a crazy freaky looking storm, although we have no clue at this point at what layers, if any, it'd be hazardous in and at what layers, if any, it'd be safe in. Lightning on Venus appears to be at least as common on Earth, but it's... weird. We're having trouble interpreting the data we've gotten so far, which has led to weird theories such as lightning bolts hundreds of kilometers long (probably not) to electrostatic "traps" that echo static from lightning around the planet, to layers of the Hadesphere that deliver a static shock to objects descending through them. But lightning flashes have never been observed, so it may not exist in the upper layers at all. Venus has crazy stratified winds that rotate much faster than the planet, leading to a "day" that's nearly an Earth week near the equator but only two days at 70 degrees latitude and even shorter the further toward the poles you go. The velocities are highly stratified by altitude, leading to great potential for wind energy. The atmosphere holds tons of mysteries still, like whether the "night glow" is real and if so what it is, or what it is that makes up the "mystery UV absorber" that soaks up most of the UV light in Venus's upper atmosphere (a benefit Martians could only wish for)
Not boring at all. It's one of if not the most interesting atmospheres in the solar system.
It would be possible to have a habitat descend below the lower cloud deck (indeed, the lower cloud layer appears to be somewhat uneven in thickness and may have gaps altogether) for short periods, wherein one could see the ground with their own eyes. Yet at the polar vortex the sky clears up at such a low height that a high colony could potentially see the stars. The ground is accessible by probes, and looks to be quite a mineral wealth - but the real life is in the clouds. Not only to fuel industry, but basically you're living in a floating Garden of Eden over Hell: vast amounts of space to live in (unlike a pressure vessel on Mars, which due to how heavy pressure vessels are, will always be very space limited), always temperate, tons of sunlight to fuel the growth of whatever tropical plants one desires, and easy buoyancy to lift a lot of them. Space on a scale that a popular recreational activity might be indoor skydiving onto the safety netting. You can even step outside and touch the atmosphere with your bare skin (just not for too long). Feel an alien wind.
For impersonal reasons, a colony there is not just appealing from the perspective of a no-mining-needed industrial basis, but also from a science basis; there's far more scientific reason to have humans on Venus than on Mars. And not just because we know far less about our "evil twin" than we do about Mars. On Mars, it makes basically no difference if you leave a robotic probe sitting around recharging its batteries in the weak sunlight while it awaits commands. You can't do that on Venus's surface. You have limited time on the surface with each dive before you have to rise to cool down and recharge; latency really does matter.
See my comment further down. I'd pick around 70 degrees latitude, 55,5km altitude during the daytime, 52km at night. A correction: the surface is not awash in sulfuric acid. Sulfuric acid cannot exist anywhere close to those temperatures at Venus pressures; it starts to fade out in the lower cloud (which seems more likely to be dominated by phosphoric acid) and completely gone by the lower haze. Also note that in none of the cloud decks are you "awash" in acid. They're acid mists, a few milligrams per cubic meter - similar to volcanic acid fogs or unscrubbed smogs on Earth. You could stand out in it (for a few hours, at least) if you had a full face mask on but otherwise no special protection (long term skin exposure to those levels however would cause dermatitis).
On the other hand, the mists are a huge *resource*. They're about 25% water to begin with, and H2SO4 heated breaks down first into H2O + SO3, and then with further heating the SO3 breaks down into SO2 and O2. So right there you have your two most important resources for a colony. There's a wide range of chemicals mixed into the mists, most of which are critical to establishing a local plastics industry, and are relatively easy to isolate and separate - the same heating system allows for fractional distillation, with an optional fractional crystallization step afterwards. So your habitat is PTFE with a ripstop (I'm preferential to UHMWPE, since it's one of the easier polymers to produce locally), and you have everything in your mists (and the air, for the Fischer-Tropsch/Sabatier hydrocarbon synthesis) to produce every step of the way - even the HF. After passing the hydrocarbons through an alkalai/rare earth catalyst bed at 20-60 bar and 500-900K, or a SAPO catalyst bed at 1-3 bar, 850K, you can recover alkenes; ethylene of course goes through a Zeigler-Natta catalyst at 1-3 bar / 300-320K to make UHMWPE, while the propylene goes into the SOHIO process (0,5-2 bar, 700-800k), mainly to recover the acrylonitrile fraction, which is polymerized (low pressure and temperature) and wet spun to make PAN, which is then oxidized and then carbonized to produce carbon fiber. Your other hydrocarbon fractions are turned back into syngas and fed back into your hydrocarbon synthesis. As for the PTFE side of the equation, there's significant HCl in the mists, which the Deacon process converts to Cl2,which is then used for the chlorination of methane to make chloroform (about 700K). This then is fluorinated at high temperatures and low pressures, fed into a neutralizaton stage (which involves sodium hydroxide recycled by the chloralkali process), then polymerized to PTFE. For your plants your nitrates are of course made nitric acid by the Haber and then Ostwald process; all local wastes are incinerated and the ash neutralized with the nitric acid, so your cations are recovered. Additional sulfates, phosphates, etc are abundantly available locally. Even iron is likely available in limited quantities; one of the Venera probes detected iron during its descent, and ferric chloride is considered a likely component of the cloud deck (possibly as a significant part of the mystery UV absorber). This would be left as a precipitate in the initial mist distillation stage.
I'm oversimplifying to a great degree here, mind you, but that's the basic layout for a starter industrial base on a Venus colony. It's amazing how much is available in the cloud decks, sucked right in through your motors (that you need to resist the meridional drift) and quite hygroscopic, so readily absorbed if you duct the thrust across absorption beds. You can also get even more if you're willing to spend the power (and ship the mass) for a cooling system to cool the interior air to below ambient, and then collect the condensation that runs down the habitat. Oh yeah, I probably forgot to mention that normal Earth air is a lifting gas on Venus... you live *inside* the envelope. More specifically, near the top, as you need the ballonets near the bottom for stability, you reduce the
In case you haven't noticed, Mars drains the lion's share of the exploration dollars these days.
It's kind of weird, really - we're far more obsessed with Mars now that we know it's a perchlorate-laden organics-destroying corrosive silicosis-risk hexavalent-chromium-laden dustscape than we were back when for all we knew there was life just sitting there on the surface. It's totally disproportionate to what we know of our solar system. If the goal was to find life, we'd be prioritizing Enceladus, whose oceans (containing a known potential energy source, H2) gush out into space for easy pickup by spacecraft. If the goal was to settle, we'd be priorizing Venus, which offers earthlike gravity, earthlike pressures, earthlike temperatures, requires no radiation protection, provides vast amounts of living space (pressure vessels = small, cramped per unit mass), vast amounts (well surpassing Earth) of energy (solar, wind), and for which all of the components of a plastics industry (and probably small steel industry as well, based on the evidence for FeCl3/FeCl2) get blown through your engines in a highly hygroscopic form from which water and oxygen can be recovered by mere heating and filtering. Meanwhile, you're sitting over a potential treasure trove where high heat, pressure and acids have been extracting minerals for rocks and concentrating them for billions of years, a region with pressures only 8% that of the deepest oceans on Earth and temperatures that can be - and have been, on 1960s Soviet tech - withstood by simple thermal inertia - and from which dredged materials can be hauled up by phase change balloon (rigid metal, contracting metal, Zylon, possibly others).
I'm all for that. Venus is a far more human-friendly target for colonization, and as for simple basic science, we know vastly less about Venus than we do Mars.
It caught them by surprise. Moon dust turned out to be a lot more problematic of a substance than was initially expected. In some ways, not in others. There were lots of worries about moon dust before NASA got there... most famously that the dust layer may be so deep and loose that it would just swallow up a spacecraft. Another hypothesis that wasn't retired until after the moon landings was that, due to its reduced nature, that it might be pyrophorric in contact with air - either immediately, or with a delay. The first Apollo mission had to conduct tests to make sure that they wouldn't destroy their spacecraft in a moon dust-triggered inferno ;)
Strangely, it smells like spent gunpowder. The reason for this is unknown; it's certainly chemically nothing like spent gunpowder. A leading theory is that the smell is again due to the reduced nature of lunar dust, something you don't find on Earth - that because there's lots of oxidation potential to it, it tends to bond well with nasal receptors.
And beyond that, you don't need soil to grow plants. Hydroponics / aeroponics are pretty much perfectly suited for Mars agriculture - minimizing the water and nutrient loads needed.
Huh? What kind of lousy "simulants" are those? Is Hawaiian volcano soil rich in perchlorates? Martian regolith is oxidizing enough that if you were playing around in it with your bare skin you'd get burns; it's similar to handling undiluted lye or bleach, highly destructive to organic matter.
It's also very corrosive just from abrasion, although lunar regolith is worse. Trivia for people here: how many vacuum-sealed samples of lunar regolith do you think we have left over from the Apollo days? Answer: none. The regolith abraded the seals over time, creating pinpoint leaks; every last sample is now partially oxidized by Earth air.
Additionally, both are believed to be very hazardous in terms of silicosis risk, akin to breathing what comes off of a rock crusher (Mars's is finer, but both are in the hazardous range). Martian regolith has some other nasty chemical surprises though (beyond the perchlorates)... among the contaminants that have been identified is what appears to be significant amounts of hexavalent chromium. That's the type of chromium almost never found in nature on Earth (because we live in an oxidizing environment) that's extremely toxic to people (think Erin Brockovich).
This isn't just Earth soil; it's a totally different beast.
Anyway, I'm not that big of a Mars fan... I'll take a colony on Venus any day over one on Mars. ;)
Also, my other thought on this topic is, air superiority and air to ground attacks are all good, but that's only half of the picture, you still have to have some sort of ground capabilities to take and hold ground. When will that go robotic?
It's obviously a lot further into the future. One envisions, rather than raining bombs down on a city, one rains down small (as small as you can) armed "rovers" with rapid reaction times to gunfire (issuing counterfire / seeking cover) and constant close communications with air support and reinforcements. So if someone does attack or take one out, they're quickly swarmed by reinforcements. And obviously if the rovers visually identify weapons they can engage targets - under human control if unjammed, autonomously if jammed. Most of the time you'd want them sitting still and conserving power (they'd either need to be able to access refueling drops on their own, be passively powered, or self-destruct when their energy supplies run out), but you'd ideally want a platform mobile enough that it could move between areas, through buildings, etc if needed, and ideally at a good speed. In civilian areas you'd want them to be very obvious and actively warn people away from them in their local language.
Counter-tactics to such weapons would obviously be tactics that keep as far away from it as possible (so that you're not at the site when reinforcements arrive) and offer no reasonable reaction time to the attack, such as IEDs. Counters to that, in turn, are more eyes looking for suspicious activity and better sensors.
Indeed. Release a drone from altitude and you don't technically even need to give it active propulsion, just active flight surfaces to control its glide. That said, with a glider or weak-powered craft, you are going to be fairly subject to winds. Then again, that only matters for some types of applications - it would be a problem for using them to conduct a ground attack or surveilance, but if you're using the drones as sort of a smart aerial "screen" against incoming missiles, maybe not.
Seems to me that the most logical approach for hitting ground targets is paired active/passive control. You make each element smart enough to carry out the mission on its own reasonably well, but have a human controlling the elements / swarms for as long as they can. So they can't stop the attack or re-route it by jamming - if they jam, it goes into auto attack mode. Which if anything would make them more likely to attack, because then you no longer have a human worrying, "is that actually a military target or could I possibly be mistaking something civilian?" - instead, a fraction of the swarm goes after the jammer while the others seek other targets in the area. You deincentivize jamming, in favor of hiding.
The two keys to cost are mass production and size. They really could get very low unit prices here. And shaped charges aren't that heavy at all. A few kilograms can take out a tank. Far less for lightly-armoured or unarmoured targets. And the smarter the attacking element, the more effective it can be with its charge - focusing on weak points or hitting areas that have already been damaged. You already see the move in this direction with modern anti-tank weaponry.
On the downside, you face risks of ending up releasing "unexploded bomblets". You really need to get the dud rate down to essentially zero for that to be acceptable in modern warfare.
Hence the other key aspect of the F-35, the sensor suite.
On the other hand, the F-35 is designed to reduce ongoing costs - both maintenance (though that remains to be proven), and basing / supply line costs.