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Man-portable air-defense systems have been around for decades, and so have been anti-satellite weapons. But while the former is a small, short range rocket, the latter is as big as a cruise missile. Obviously, it is impossible to make such a small rocket go high enough to threaten a satellite.

Or is it?

Satellites are fragile, have a predictable orbit they cannot meaningfully alter, and have no counter-measure. So the rocket doesn't need acceleration or agility beyond what is needed to reach a specific point at a specific time. The launch itself can be timed to the second.

The smallest orbital rocket to be built was big enough to require a truck, but we aren't trying to reach orbit, only orbital altitude, which requires several times less fuel - which is why sounding rockets attempting to reach space are so much smaller than orbital rockets for the same payload. And we don't even need a payload, only to hit the satellite. Unless, of course, a small explosive charge gives the resulting cloud of debris a better chance to hit than the same mass in sensors and guidance.

So the question is, can an anti-satellite rocket be made small enough to fit a man-portable rocket launcher?

The total package must be, if possible, less than 35kg and small enough to be carried as a backpack. Or, if impossible, to be carried in separate components by the smallest possible team.

It must at least reach low orbiting satellites, so let's say 250 km minimum altitude for a vertical launch. The higher the better, though, both to give more launch sites and to reach higher satellites. We can even go for a range of rockets with varied capabilities. Being able to hit the ISS at a bit more than 400 km altitude would be great for advertising.

The fastest the setup on launch site the better, up to a few hours. More time can be spent setting parameters up in advance, though. Simpler setup procedures are also better, but not mandatory, as skilled operators can be trained anyway.

It must require no fixed infrastructure, not even a perfectly flat ground. If fueling is required, the fuel reserve must also be man-portable. Same thing for ground-based sensors or a ramp.

Toxic fuels should be avoided if possible, but if it can't be then something must be included to protect the crew during storage, transport, setup, and launch if they have to be close. Also there is toxic and toxic. White fuming nitric acid may be manageable, but chlorine trifluoride is right out.

it must be possible to store the components in standard warehouses for long periods, so corrosive, unstable or cryogenic fuels are to either be avoided or extra step must be taken for them.

The higher chance to hit the target the better, but less than 100% is acceptable. Let's avoid going below 50% if possible, though.

Don't worry too much about R&D cost or legal concerns, assume I am an evil billionaire with my own island lair and a plan to Conquer the World!, and I bought a few missile and aerospace companies to tap their skills and cover up the tests. I don't have access to nuclear materials, though, nor metallic hydrogen (whether it works out).

On the other hand, once mass-produced, the individual units should not be too expensive. Let's say less than a million dollars.

Assume the starting date you want from the 1960 up. Before is better, but if you need experimental tech like ramrockets or even fancy near-future tech like rotating detonation engines, so be it. Please don't go too far in the future, though.

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    $\begingroup$ It isn't just a question of range. One degree offset at 500 m is negligible; at 5000 km, it would miss by several dozen miles. There's also the change in g, the time to reach the satellite,taking into account the distance it would have moved, and atmospheric refraction that you'd have to calculate and correct your trajectory on the fly, in this case, literally. Part of the reason for needing cruise missiles is that they have an onboard computer to do all that $\endgroup$ – nzaman Jul 26 '18 at 12:07
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    $\begingroup$ The total package must be, if possible, less than 35kg. That amount of fuel is getting you nowhere, so no, it is not possible. Note that you need powerful fuel to push through the atmosphere, things like an ion drive won't work. $\endgroup$ – Jan Doggen Jul 26 '18 at 12:10
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    $\begingroup$ What about some kind of auto-targeting laser? With a computer to direct where it needs to be pointed, it might be enough to cause some damage to the satellite. $\endgroup$ – Sydney Sleeper Jul 26 '18 at 12:16
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    $\begingroup$ @SydneySleeper, the issue with lasers is how much they diffuse through the atmosphere, there was an experiment many years ago, where they tried to signal the ISS with giant spotlights and used a ver very power blue laser to aim the lights, and the scientist (who was aware and participating in the test) was able to clearly see the blue laser from space, but received no damage to his retinas despite on the surface it being many many times more than powerful enough to do so $\endgroup$ – Blade Wraith Jul 26 '18 at 12:33
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    $\begingroup$ What about hacking? Take control of the sat and send it an instruction to come down. Would it be a valid answer? Or do you only consider sending some explosive up there? $\endgroup$ – Legisey Jul 26 '18 at 13:32
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Interesting question... and as an entire thing... No. because of the first paragraph below

Several obstacles to overcome, target acquisition and aiming of the weapon, but i'll leave those out since they are definately NOT man portable, and i'll ignore the factors of if you can base the detection somewhere else why not launch somewhere else arguments to the side. lets assume you have the ability to detect your target, and aim your weapon accurately enough

One of the major considerations is how to destroy said satellite. if the weapon needed a detonating charge then it would need to have a warhead... increase mass therefore more fuel required, more fuel means more mass, more mass means well... more mass. its an exponential increase. however if the rocket was dumb, and just used the fact that it needed to reach orbit and then let the satellite collide with it and the vast difference in velocity would be all that was needed then the rocket doesn't need anything other than guidance systems , perhaps a tiny amount of propellant for final adjustments, but the issue with this is then you need to be even more accurate.

The SS-520-4 rocket is a modified sounding rocket and is the lightest and smallest launch vehicle to send a payload to orbit, however it weights 2.4 tonnes... not quite man portable, and the payload was 3kg...

BUT

You weapon doesn't need to reach orbit, just to reach orbital altitude, this is a lot lot less DeltaV required so something akin to the S-210 would probably almost do, its another sounding rocket, only designed for ionosphere study but it can reach 110km... so it can get close to Low Earth Orbit altitude which starts at 160km. 5.2 metres long, 0.21 metres wide, but... 300kgs... but its been around since the 1960s. and they still carried a few kilos of payload in terms of a small sensor setup for the study. Remove those few kilos and maybe... just maybe you could reach 160km. but that's only the start of LEO altitudes, LEO technically goes up to 2000km

There are ways of reducing size and increasing power. SpaceX super cool their fuel in the Falcon's, this means they can have smaller fuel pumps put keep the same flow rate of fuel, smaller pump means less weight, the fuel is still the same though. a larger rocket could make do with being multistage, constantly dropping excess mass as it gains altitude, but such a small rocket would probably be heavier by adding extra stages which would require extra engines. and again, simply down to the mass of the fuel. i don't see being able to get it down to 30kgs, you're wanting more power

Hmm...

An even older rocket, the MT-135 again a sounding rocket, had a max altitude of 50km... but it could lift a payload of 10kg. and the eitre thing was 68kg, that's a team portable rocket... and maybe without a payload so down to 58kg. it might be able to do 75km

The Rohini rocket family, built in India has some very small sounding rockets, so i'd advise you look through the worlds various Sounding Rockets, remember if its a dumb weapon (meaning its just an impactor nothing else) then your making the whole thing lighter which means same fuel more altitude, or same altitude less fuel therefore slight smaller.

but Alas, that first paragraph does come into it as well. you'd have to overcome those issues before you even bothered to start designing the weapon system itself. the weapon could easily be truck mounted, as the SS-520 could be, its small and light enough for this, but again the "everything else" needs a lot more infrastructure

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The answer might be to avoid rockets at all (or at least for everything except for the final adjustments to strike the target). Your issue is to lift a payload to orbital altitude so the orbital track of the target satellite intersects your payload (as noted, you could increase the chance of a strike by launching a bucket of ball bearings for the satellite to fly into. At 7 km/sec velocity even a ball bearing will have a great deal of kinetic energy).

So I will suggest a portable railgun.

The "gun" itself would likely need to be assembled and mounted on a large tripod, but the components of the railgun itself need not be very massive, you would essentially be assembling sections of rail to build the "barrel" (and there are non conductive bridging parts to keep the barrel rails aligned).

Since you don't want a heavy energy source, the device is powered by a portable MHD generator, energized by the hot, high speed gasses delivered by an explosive charge. In some ways this would resemble a recoilless rifle, your team would load the casing with the energy source, connect the wires and retreat to a safe distance. When they initiate the device, a stream of hot gas is created which flows through a venturi and then the MHD generator itself.

enter image description here

Real life portable MHD generator http://jpaerospace.com/blog/?p=5096

We know the US Navy's projected 64 MJ railgun is designed for a range of over 200km, and the trajectory is actually outside the atmosphere at one point, so what we really need to calculate is how much energy would be needed to fire a projectile to orbital hight. Some of the uncertainties would include the mass of the projectile and the efficiency of both the MHD generator and the railgun in converting the electrical impulse into thrust. Given the potentially huge amounts of energy being released in a very short time frame, I would say this is very much a "one time use" weapon, the rails would vapourize as the projectile is being launched.

So the rough setup would be:

  • 1 man carrying the disassembled railgun rails
  • 1 man carrying the tripod assembly
  • 1 man carrying the MHD generator and associated cabling
  • 1 man carrying the charge
  • Team leader to supervise the setup and aim the assembly (either with the use of a laptop loaded with the orbital information of the target, GPS and very good set ofbinoculars), or good communications to the targeting centre. Team leader also carries the warhead.

The five man team could likely carry all the parts and move to the launch area in a large 4X4 pickup truck or a pair of SUV's if additional mobility and speed are required. The use of a truck also allows carrying spare rails and warheads to allow additional engagements. Security personnel may be added depending on the situation.

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    $\begingroup$ Isn't the acceleration provided by a "few meters long at maximum" railgun too high for anything except a bare sturdy metallic bullet? I've also thought about railguns but i got stuck because of the aiming issues and -afaik- we aren't even close to have some electronics tha can withstand something similar to the 64 MJ railgun acceleration (it's not a matter of railgun's raw power, because it depends on the bullet wheight, the issue is the required acceleration). $\endgroup$ – theGarz Jul 26 '18 at 14:58
  • $\begingroup$ @theGarz I don't understand the physics well enough to have any clue whether this is feasible, but what about a canister of bearings, kinda like a sabot? Assuming the canister makes it most of the way to the orbital path, I'd expect wind resistance to eventually drag it down faster than the bearings, and the bearings would start dispersing near the peak of the trajectory, and start scattering, leaving a small cloud of bearings for the satellite to fly through. $\endgroup$ – Doktor J Jul 26 '18 at 17:47
  • $\begingroup$ Alas, the Halfbakery is down. Linked: my scheme for a satellite sniping railgun, courtesy of the Wayback Machine. web.archive.org/web/20171015073018/http://www.halfbakery.com/… $\endgroup$ – Willk Jul 27 '18 at 3:01
  • $\begingroup$ @DoktorJ: i was worried about "the final adjustments to strike the target", which require some kind of navigation and control, therefore some gears and electronic. The issue is the tremendous acceleration of the railgun bullet, which seems to be too much for a missile. It will collapse under its own inertia. On the other hand some kind of navigation would be required. Hitting a 2m large satellite is like to shot a needle to 25cm large target, 5km far, moving at 250kmh, and you have hurricane wind in between. Good luck! :D $\endgroup$ – theGarz Jul 27 '18 at 7:59
  • $\begingroup$ @theGarz I'm wondering though, if the canister is sturdy enough (titanium alloy or some such) and the bearings depart the canister early enough (but still with significant upward velocity), wouldn't they scatter and create a veritable minefield for the satellite? Thinking about it, it's actually a sort of flak cannon, trading off penetrating power for denial of a larger target area. $\endgroup$ – Doktor J Jul 27 '18 at 14:13
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Current anti-sat missiles do exist, and they are attached under the wing of a B52 and flown to high altitude before launch if I remember correctly. They couldn't be reasonably called man portable. Of course if your atmosphere was thin and the planet smaller with lower gravity that might be a different problem.

Otherwise you could do it with pre-deployed ordinance. The guy on the ground carries a remote. A large satallite mine was deployed in space years ago. On command, a ball bearing is jettisoned into an intersecting orbit. Perhaps this ball bearing has an attached thruster assembly for making fine adjustments to position itself correctly.

There is also the issue of the height of the orbit. Which is to say that geo-stationary is way higher than low earth orbit. So probably your mine would be in geostationary or higher orbit, and the thrusters would be used to brake the ball bearing down to the appropriate altitude.

Kessler syndrome might be a factor in the design. Perhaps a more friendly approach would be that it is a ball of sticky gum instead of a ball bearing, and within that goo, is a heater (to liquify it as it approaches) and a long antenna that spools out. The goo captures the satellite. An EMP charge is fired directly adjacent to it to destroy its functionality, or perhaps a long term jamming frequency is emitted. Then a long antenna is spooled out to use atmosphereic drag to eventually deorbit the thing. Instead of gum, maybe a fine mesh copper infused cast net, which would essentially Farraday box the offending sat. Extra points if the net has sinews, such that as it wraps around the sat, it tightens to itself. Maybe even constricting to crush it, like a python.

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What if you didn't carry the fuel?

"the latter is as big as a cruise missile". But that cruise missile is mostly fuel. What if you were near water and could make liquid hydrogen and oxygen. Put the rockets on the top pointed downish and have a slim dangling light fuel tank. Hey why aren't engines on the top of rockets? Fuel pumps? We don't need no... OK so our super light and strong and heat resistant fuel tank we just pulled out of our backpack also needs to compress the fuel up and into the engines against all the acceleration.

If there was some way to make solid rocket fuel using stuff in your backpack this would be easier. Then you just need a long flexible tube that becomes rigid when filled with solid fuel. Double-base (DB) propellants sound a lot like dynamite but with nitrocellulose instead of dirt (sounds safe). Maybe you engineer a fungus or virus or a combination that rapidly converts plants into nitrocellulose and nitroglycerin using the plants own machinery?

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  • $\begingroup$ I recommend looking at the Mini-MAV stuff from a few year back, the mars ascent vehicle, getting into orbit from mars is a lot easier than earth and their issues came from the fact that the guidance systems, reaction control etc were almost 10kg, and then the payload was only for 500g of martian dirt. the entire rocket would have been a more than 35kg. But this rocket would need to reach the orbital height from earth not mars, so thicker atmosphere and higher gravity, even making fuel on site, you still need to carry around the structurally sound container for said fuel... $\endgroup$ – Blade Wraith Jul 27 '18 at 9:11
  • $\begingroup$ e-reports-ext.llnl.gov/pdf/363904.pdf $\endgroup$ – slOOP Jul 27 '18 at 23:46
  • $\begingroup$ Thanks. I was surprised that the rocket portion was so small. I understand present day it is not possible but i feel like you could do a near future solution that wouldn't sound too far fetch. $\endgroup$ – slOOP Jul 28 '18 at 0:01
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edited as I thought of 3 possible ways

1 - 3 step Rockoon gun

I'm thinking of a multi stage system will work best, each layer of the atmosphere has different needs to problems to overcome:

  1. High altitude balloon will provide the first stage, this can reach about 30km (this height is common for this type of HA ballons to achieve as evidenced in the link) and pass the majority of the atmosphere with it's payload being the 2nd stage
  2. the second stage will be a conventional rocket, a so called Rockoon will give the 3rd stage an extra boost while aiming the the barrel of the 3rd stage so that the final payload launched from it will hit the target, there are plans from JP Aerospace to use this Rockoon config to reach space on it's own
  3. the 3rd and last stage will be an gun, the payload to take down a satellite can be a single ball bearing as stated in other answers and at the height where it's fired coupled with the initial speed from the 2nd stage rocket it should have more then enough speed to destroy a satallite, it's worth mentioning that at those heights there's barely any atmosphere slowing the projectile fired down.

2 - Hacking

All satellites require some form of communication to the ground, and a laptop with a cellular modem and/or radio antenna (depending on if the satellite or it's C&C center is connected to the Internet in some way or it's a purely RF hacking) is way under the 35kg limit, if one manages to hack the satellite it could destroy it in a lot of different ways:

  • some satellites have a limited form of movement ability, this is to move them out of collision with space debris (and other satellites) you could use those engine to steer it into something or down the atmosphere, you don't even have to hack your target, you can hack another satellite and ram your target.
  • It's been speculated that some military satellites have a self destruct ability.
  • Change it's direction so that it's pointing away from the sun and with no solar power it's battery runs dry and is affectively dead.
  • rotate it so it's antenna is no longer pointing to earth and it can no longer be controlled by anyone (might not be possible on all satellites depending on their design)

3 - Lasers (everything is better with them)

An Wicked Lasers arctic is a 3.5 Watt laser that costs 300 bucks and weighs 421g, that means you can have 83 of them to get 290Watt of laser power in 35kg (there is still a bit of weight to spare which will go to a concentrating lens to get the focus point of all those lasers right at the same spot of the satellite, most will dissipate at the atmosphere along they way but enough will go through to manage to hit the satellite and destroy it's more sensitive parts - cameras, solar panels, etc... and at a price of 25,000 $ you can't afford not to buy one.

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    $\begingroup$ High Altitude Balloons invariably weigh a lot, and also take a long long time to reach apogee, so i'm not sure that would be suitable as a weapon system, especially as most satellites orbit the earth every 90 or so minutes, about the same time it would take for the balloon to ascend, so you'd need to "fire" your weapon at least a full orbit before impact... aiming will not be easy. and ground based lasers wouldn't effect a satellite as to how much they diffuse in the atmosphere. hacking is an option though $\endgroup$ – Blade Wraith Jul 27 '18 at 6:56
  • $\begingroup$ How the stage 2 rocket should/could aim the desired satellite? The laser definitely won't because: a) it's a blue laser, and because ofthe same reason why you see the "blue" sky, the laser beam will diffract. b) The idea to focus 83 lasers at 250km is simply not reasonable. With 3.5W you won't even mark a metal surface at close distance, you have better chance to try to heat the satellite (heat dissipation is quite an issue in space) but how can you constantly point something that's few meters wide, travelling at several km/s, hundreds of km away? $\endgroup$ – theGarz Jul 27 '18 at 16:12

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