PB666

It takes very little dV for most satellites to clear them from LEO, since a good segment are between 250 and 500 km. Let do the math for 500 km rpe = 6371000 + 120000 = 6491000. rapo = 6371000 + 500000 = 6871000 a = 6681000 (Note to YNM this is atmospheric breaking) since the craft will be deorbited at rapo to intersect rpe we want to know the starting and final velocities at apo. Assuming a circular orbit. V6871000, cricular = 7616.6 V6871000, a = SQRT(µ (2/r - 1/a) = 7507.47 dV = 7616.6 - 7507.5 = 109.1 m/s. Lets say you have a six ton satellite that can only thrust 1/3 rd of the time. The disposal vessel weight say 1000 kg with 4 Bit7 thrusters (44 mN) . So the total mass is 7000 kg. and the time required 3 * 109.1 m/s * 7000 kg / (86400 * 0.044 N) = 603 days. This requires a power supply of 1800 watts (the weight of the thrusters is trivial). If you add more thrusters of course you need more power. Note the number of thrusters is really dependent on the amount of power available. But with four RTGs the tug, somewhat less efficiently, retrograde over 270' instead of 120 degress and markedly speed up its operation. dv = 109.1 = 3300 * 9.8 * ln (Mi/Mf) = 0.0033 * 7000 = 23.65 kg of fuel, with about 1/7th of this it can return to orbit. So that the total cost is 30 kg of fuel. Lets say the satellite cost 2 million dollars and it has on board 300 kg of fuel. Then it is possible for it deorbit satellites at the cost of 200,000$ each plus the cost of launch, since its weight is around 1 ton, y could be launched on a single SpaceX for about a third the cost of an ESA launch. In addition the satellites, being self propelled could return to an argon tank (8000 kg) in LEO and refuel, then go about deorbiting many other satellites. So basically 8 satellites could be deorbited over the period of 2 years or 4 per year, over the course of say 40 years this could be done 20 times per satellite or 80 satellites deorbited. That all cost of 2 space X rocket launches, so how much is ESA planning to spend each launch. Of course for satellites in much further orbits this is more difficult and may require more thrusters.

One could have some other propulsion system. ION drives are decent for moving light things (on the order of 20 kg) their weakness is for heavy things. As discussed before What is the power supply. Solar. If you increase the mass of something you increase the volume, that increases with the cube of average radius, panels increase with the square therefore an object with panels with roughly the same surface area as the object itself, the power increases with the square. As you decrease size your power density goes up which means the ability to accelerate goes up, because of a lower structural basis the weight per unit panel can go down. This can be a small as a film on the surface of the wide rectangular cube sat. Objects travel in orbits, if you are planning a hohmann transfer you need lots of power, however hohmanns are not the only way to get to the target. Because ION drive can spiral, the potential and kinetic energy differences they have with objects already in orbit (with comparable angular positions) is small relative to objects approaching from hohmann transfers. Is simply a matter of approaching, slowing down a few meters per second. How to capture. Most satellites have solar panels, the system could deposit a probe with a very fine spider silk thread, it could basically make a trip around the devices panel and return to the parent ship, magnetically attaching. We are talking about speeds in the 10s of millimeter per second range. The ship returns and the parent device slowly reels the two craft closer together. After this the parent device determines the retrograde direction and using a combination of steering instruments slowly decelerates the craft at apogee so that its perigee is low enough to decay. Once complete the parent releases the thread and powers itself back into a stable orbit. For objects in GTO, it is something like 11 m/s to gain a graveyard orbit, but ION driven craft could actually push the craft into heliocentric orbit with 10s of meters per second of dV using the moon to aid in its exit. Once in an escape orbit it tosses. ION drives will be the future of space garbage clean-up for one very simple reason, you don't want to put trash in space to haul trash from space on a 1:1 ratio, they have to be capable of completing multiple garbage disposal missons. Hydrolox cannot do this, hydrogen burns off. Metholox, oxygen eventually burns off, everything else is too low of ISP to accomplish multiple missions.

And so, any new process is going to draft developed technologies for new application. ESA already tried harpoons with the Philo lander, and guess what, they FAILED! I didn't specify either how to put clothes in a washing machine to wash them or how to chop carrots for a beef stew. One assumes that if a agency is dumb enough to try to harpoon satellite with velocities sufficient to penetrate quarter inch aluminum plate that they are at least smart enough to devise a communication system for a rocket. Course again given their progress on the Orion service module that is a valid question.

That's where Elon hides his secret stash of munchies.

Easily solved problem, have the practice on the low hanging fruit, since the bots are small if they target junk in low orbit first, if they develop problems their debris quickly decays into earths atmosphere, well below the danger zone. BTW without chemical fuels where is all the inertia for hurling into higher orbit going come from. Living in the stone age still? You do realize that ION driven steering factor thrusters are already on the market. https://www.accion-systems.com/tile http://www.busek.com/index_htm_files/70000700 BHT-200 Data Sheet Rev-.pdf http://www.busek.com/technologies__ion.htm https://gizmodo.com/5935973/penny-sized-ion-thrusters-could-steer-the-satellites-of-the-future Communications is an old problem. There are robots than can manage all by themselves to do tasks, so this is just a matter of learning algorythm in space. Any decent computer can set them up to rendezvous. Might take a while but they have all the time they need. All this stuff is pretty self contained, unlike what would happen if you carelessly harpoon a satellite. Once again you exaggerate to the extreme and you are pulling emotional arguments. There is nothing about the guidance system that cannot be modeled. The only under-performance problem is the lack of sufficiently light solar panels and sufficiently efficient small ION drives with 1500 to 3000 ISP.

That's true another solution. If you harpoon it the harpooner goes down with the harpooned.

Thats probably the bigger problem, as SX catches up they are getting even a longer list of customers, they need to be doing 1 per week now.

I have a solution for small pieces. its a bit like a crab trap. with a flexible opening. Again all these systems are ION electric based. By some other means you locate the small debris. Approach the debris such that the debris falls into the open with just enough force to push through, it is then trapped in a carbon fiber mesh, then move to the next piece once the bag is full the ion drive places the entire thing in an unstable orbit, releases at opogee and climbs out of the unstable orbit pops open another trap and then captures the bag from its back side (the bag would have three hooks which could be grappled. Repeat process. Once the bag has a ton of mass its released. So in response to DerekL, there are many non-invasive systems that could be deployed. the Harpoon based system is, in comparison, a very bad idea.

lol, ummm, focus on what customers willing to pay 4 times as much?

Uh huh, and of course if it hits the wrong part of the craft, you then have 10 or 100 pieces of space junk instead of 1 piece to deal with. There are other ways do deal with the problem. Space bots are mearly a matter of propulsion system (ION drive on electrical teather) and a guidance system. Its not a fusion reactor in space. If space X can land from a trajectory going the opposite direction, bots in space can tether. In fact some sort of vacuum pliable adhesive would also do the trick. With ION drive based systems you would mearly need a 5 directional (one drive and four steering, about 6 kg, about the same mass in fuel) and ideally tap into the satellites power system. This could place the craft where part of the orbit is below 130 km, it will decay on its own quite rapidly. You could have 10 or so of these things in a single cube sat that searches out all rouge satellites that have similar orbits. Not that expensive. All you would need is an ION drive based 'tip' on the device, a glue that is eject in the moment before collision at some ridiculously low velocity and release the tip to wander off with the satellite. Whatever is going to be done needs to be done soon, the number of satellites is rising exponentially and trend is economics based, going to get more productive once SpaceX is launching their own PLs for commercial apps. Lots and lots of satellites running around in LEO.

http://www.bbc.com/news/science-environment-43418047 This is too incredible to be true. How much more risky could this be. Why couldn't you have little space-bots deploy that tie rope around the rogue satellite, much safer, much less risk of a object disintegrating event.

Falcon Heavy _is_ working, there is a launch to occur soon with a paying payload.

Make a half or quarter scale length, some length in which the final speed is less than x. Then measure h at apogee and make some assumption about burn time. From that you can determine dV by determining velocity at end burn based on h and final h (or better the velocity at end burn). Vend burn = (a * burn time) - (g * burn time) = (a - g ) burn Time = V or a - g = V/burn time T/m = a/burntime + g m = average mass. If the PL of the rocket is sufficiently large then velocity will be low and the relative mass difference is small, you can calculate T * time pretty easily. A simpler and far less sophisticated way to do it is take 4 fishing scales (they need to be tuned to the rockets theoretical thrust) and mount them to the rocket in such a way that when it fires you can see the weight and multiply it be 4. BTW, playing with SRBs is dangerous.

Global warming. . . . .no wait, global cooling . . . . .hmmm, climate change . . . . . Gremlins throwing smoke bombs . . . . . . . Alien experiments!!!!! How about just ordinary Jupiter scale weather.

f = w/2π f = 1/P therefore w = 2π/P = 5.53 x 10-20 If hydrogen at an exterior point of a galaxy means that it is akin to the hydrogen being on the surface which is moving with respect . Its velocity is given by SQRT(µ/r) or alternatively w2r = u/r3 where w = SQRT(µ/r3) = µ0.5 r-1.5 r1.5 = µ0.5/w r = (µ0.5/w)2/3 Since P is constant, f is constant and since f is constant w is constant. r = 7 x 1012µ0.333333 The mu for earth is 4E14 and the sun is 1.4E20. if the galaxy is say 1010 times larger then is means that the width of a typical galaxy is roughly 1033 or 1017 light years (larger than our visible universe). Since it is pretty certain that galaxies are not that large we can pretty much argue that what ever particle they have found or our sense is not on the periphery of a galaxies mass. And then if another person with more sensitive equipment is measuring, then they are finding hydrogen further away traveling at a different speed. Since we cannot observe this and since it is likely that comoving space-time has some constraint on how large galaxies can ever be in size, its relatively easy to postulate that what they are measuring is in dynamic equilibrium of a galaxy and its surrounding space, means that it likely on some sort of aberrant (non-orbital) trajectory with respect to the galaxy.

I did say '"an exterior point"

Im going to wait for the dust to settle on this hypothesis. Possibly true but sounds a bit fantastic. Maybe it has to do with something else, like the time interval between collisions of major galaxies.

ESA is responsible for the Orion service module also. So its that logic squared.

But SpaceX will make more profit. These are just some of their contracts. Apparentlt they a committed to 100+ launches. http://www.spacex.com/missions

I does, like what is the Royal Astronomical Society and what are their credentials.

Apparent 1.1E20 sec is the time it takes for any spiral galaxy (an exterior point) to make on revolution. http://blogs.discovermagazine.com/d-brief/2018/03/14/galaxies-rotate-billion-years/#.WqnRW-ch2Ul This disclamer is that its not as good as a swiss watch, though I seriously doubt switzerland or watches will be around in a billion years to compare with. Edit: sorrry left out a term.

Well if you are going to go that direction . . . . .

Loaded mass = Empty mass + Fuel mass Flow rate = Fuel mass / total burn time dV = Ve * ln (Loaded mass/Empty Mass) Ve = dV / ln(Loaded mass/Empty Mass) Therefore if you know the loaded mass and the empty mass, and if you measure the change of velocity. ( A good place to do this is from the orbit of a large gas giant where the trajectory would be flat over the burn) Also you can determine thrust (say at 10 seconds after the burn starts).

What we need is an administrator that increases performance and can make the case to the people why NASA's budget should be increased, but . . . . . .

The problem with ISP is weight is relative to earth's surface and there in no cogent metric equivalent (the slug, not an international unit). When you are in orbit you have no concern of surface weight at all.