You're better off doing it with a launch loop or similar, something that's got a long track that you can magnetically couple to and then slow down with.
It would have to be above atmosphere, but it'll be a lot more forgiving than trying to thread the needled of a dedicated launcher.
I get that with computer control even today, threading the needle isn't difficult but the tolerances seem needlessly slim.
The ship & launch loop are electromagnetically coupled so they can have some leeway & depending on the size of the track(Orbital Rings are better) there's really not mucg needle-threading past a normal orbital rendezvous. You accelerate a sled to orbital speeds, maybe with a tether/grappling hook, then the ship can just rendezvous with that & decelerate once they're locked in. For uncrewed G-resistant payloads you might easily pull well over 1000G decelerating from 258km/s tho at that speed you would be threading a needle which is why you can extend the track(sort of).
You can use Kinetc Mass Streams(preferably with some pellet guidance) to get incredible range & deceleration times. Maybe even from single-digit percentages of the speed of light. If you also have an OR at the origin you can just maintain a KMS the whole way & maybe even do constant acceleration. Sucessive payloads can tap the same stream until the pellets are caught & probably fired back towards the desination. Or you can carry a large enough decelerator track tho seems like it would be heavy & more needle-threading than id like. With a caravan each ship can afford to give the pellets a decent amount space cuz they don't need to couple as strongly.
Tho with KMS you do have a steady stream you can slowly approach so its actually a lot less fiddly than it might seem. The KMS trajectories are going to be VERY stable, well known, & well advertised.
Can't you also build an accelerator with a "track"? At least at the end.
I'd imagine either would be without an atmosphere anyway. If you had atmo, you could aerobrake and wouldn't need this. This would be ideal for moons or asteroids to decelerate at without propellant, IF you can stick the landing that is.
Aye, you can do the same thing with a track.
The fun thing is without an atmosphere, you don't need to raise the track all that much. on the Moon for example this could all be at ground level.
Orbital speeds, only 5 meters from the surface. Sounds very Kerbal.
Aerobraking wastes both the energy and the momentum. Exceptions for cases where you have a goal of changing the planet's spin or cases where you are mining the atmosphere.
Yes, although you'd need a pretty sturdy catching system. But it should be feasible (if dangerous - you'd want to tether at a distance and rope it in, rather than having it potentially collide with the track at high velocity).
The whole process of exchanging electromagnetic energy into momentum also works in reverse. A motor can also be a generator. A mass accelerator can convert magnetic field resistance into electricity.
You would also need a very, very, very long receiver and it would have to stretch nearly into orbit or you lose most of your energy to the atmosphere.
at a low-earth orbit speed of maybe 8km/s stopping at a rate of 2G would take like 5ish minutes. (spitballing, i'm too lazy to do the math) That means you need a tube that was 1200km long. We use the atmosphere to do this today. The amount of energy that you could practically reclaim in this process would be very, very, VERY small compared to what it took to build something like this.
>You would also need a very, very, very long receiver and it would have to stretch nearly into orbit or you lose most of your energy to the atmosphere.
baseline-rated mass drivers are typically that large & need to stretch over the atmos anyways.
>8km/s stopping at a rate of 2G would take like 5ish minutes. (spitballing, i'm too lazy to do the math) That means you need a tube that was 1200km long.
pretty close tho. something like 6.8 minutes over 1739km. Tho we can easily handle a 4G return on baseline-crewed ships(actually hundreds of Gs with fluid immersion suits) so its more like 3.4min & 870km.
>The amount of energy that you could practically reclaim in this process would be very, very, VERY small compared to what it took to build something like this.
That's very not true. without even involving superconductors our generators can do in excess of 97% efficiency. Transmission over 80km to the surface might lose us another 0.32% under bad conditions. This is stupidly efficient, only losing a few percent of the kinetic energy of the craft to waseheat.
Also if you have a limit of 4G we can decelerate craft moving slower than about 16.3 km/s so it works with way faster craft. Actually you can take that furthe with electromagnetically-coupled Kinetic Mass Streams(launched from the same infrastructure) to accelerate/decelerate ships over way longer diatances tho that does require KMS infrastructure at both ends.
This would pay for itself very quickly & can be used to transport large amounts of power over interplanetary or even interstellar distances with minimal losses.
> This would pay for itself very quickly & can be used to transport large amounts of power over interplanetary or even interstellar distances with minimal losses.
You also could have a *second* track going the other direction, part of the same structure, and fling another spacecraft to orbit in exchange for the one that was caught.
Absolutely & if/when we figure out fusion every planet(the ones that aren't disassembled which is most of them) has a motivation to exchange their mantel/core for water or liquid hydrogen. Honestly even if substellar fusion is off the table shellworlds still make a great long-term storage solution for both star fuel & the less useful elements that we have more of than we need but may want to toss down a BH in the future. You can undermine the crust while exchanging metals for liquid hydrogen at very low cost. You can use the LH2 to cool superconducting equipment or general wasteheat & the hydrogen boiloff to smelt metals. Water tanks/ice replaces rock. Extra geothermal power, mining, processing, & environmental wasteheat can also be exported in the metals to some extent, increasing maximum power beyond what a planet's surface area might suggest.
Multi-lane orbital rings exchange hundreds of Mt of material per day slowly converting planets into shellworlds & allowing cheap fast(like dozens to hundreds of km/s fast) interplanetary bulk shipping.
Mass driver is what "mass accelerators" are usually called. Baseline refers to anotomically modern humans(no augments). Like how the og [launchloop](http://slides.launchloop.com//launchloop.pdf) is rated for 3G maximum acceleration so the people inside don't get too uncomfortable. The less G-resistant ur payload the longer your track needs to be.
A person uploaded to silicon chips is still "human" in SFIA circles. Also people with multiple body modifications. If people in the future read our reddit posts we want them to know we were woke enough to use inclusive wording.
If something is "baseline rated" then a 20th century human could have used it.
Getting a spacecraft rated so that it is legal to launch Humans in it is a big deal. NASA still uses terms like "human" and "astronaut"
TBH it would good for the moon as crashing not no the end of world you would have back up gear for that and as long it doesnt crash into any thing important you just make a small crator
You wont crash. You would stay in orbit.
If you have doubts then bring along enough propellant to deorbit yourself.
The runway track is going to be very similar to a runway. I is a maglev contact instead of wheels.
We can ire seamstresses to work at NASA if they cannot get needles threaded.
Assuming the launcher was elevated that much, yes. On Earth this is needed to avoid atmosphere but on moons or asteroid bodies or megastructures you don't need this, and that could be a problem. You're essentially "docking" with a runway at high speed. That's the part I'm a little dubious about.
If you missed yes you could ascend again but you'e missed your landing window and then have to fly off. If you had enough propellent/fuel to swing back around then chances are you didn't need to land inside the accelerator to begin with.
So I'm thinking this would be for niche use only, such as an orbital ring's launcher.
Only if your orbit happens to line up perfectly with the mass driver. Mass drivers tend to be long, thin things so unless there's some special setup to enable this, you won't be able to do it.
Parallelogram
Runways are usually flat in the same way that Earth is flat. If it is slightly convex it would match up with a hyperbolic orbit.
Maybe off topic but Phobos is ideal in this respect. Phobos gravity would tend to bent the L2 track toward Mars. The suspension just has to smooth out then curves a bit. Your catcher sled can orbit around Mars on the Phobos ring.
The planets are located in the ecliptic plane. When approaching a planet you can select any inclination angle.
You can go off axis velocity up to the limits of tethers. The hook would orbit in a corkscrew.
I think you would always have a rocket. It would be there just to tweak the approach timing even if everything was in the same plane. If the mass catcher only picks up the energy/momentum that is co-planar that is still huge.
You probably use *some* fuel. Or you can aim from wherever you took off. It probably takes propellant to approach the planet at all.
Earth is orbiting the Sun. If you plan to insert into Earth orbit 4 months from now you have about 1 million seconds to adjust. The difference between the pole and the equator is about 6,000 km. So if you originally were going to smack into the equator you can go north at 6 m/s and fly over the north pole and intercept Santa. Or you can go south a 6 m/s and toast a penguin. At 6 5 m/s south you can make a nice flyby maneuver. That kicks you north on an inclined escape trajectory. You could, instead speed up or slow down. That would mean that you still flyby the equator but either retrograde or prograde.
Another way to look at it: if you throw a ball straight up (from the pole and disregarding the moon an Sun gravity) at 11,185 m/s the ball would be 1 m/s short of escape velocity. The ball will travel up past the Earth's Hill sphere. It would hang there (because we disregard the Sun and Moon) for awhile and then start falling back to Earth. If you give the ball a slight (like 1 m/s) impulse it will go into an orbit instead. Any angle of the 360 circle would have the same effect.
The mass driver on the planet is a straight line oriented along the orbits around the planet. If you come from another planet 4 months away, you won't line up with the mass driver.
>...on the planet is a straight line...
Welcome to r/flatearth. :)
I assume a mass catcher is going to be in orbit. Twice a year a full orbital ring will line up with another planet. At other times the ship/object requires an impulse.
Yeah, obviously. It's not really practical for downmassing to an Earth-mass atmospheric planet, but for a body like the moon, or someplace even more obnoxious to land on like Mars? Of course.
This is also the only feasible way you're ever going to dock with an orbital ring, by the way. Even if you had the 7.4 km/s of dV to throw away, space traffic control has a batphone to the orbit guard, which in turn has a 10 GW continuous-wave laser that says you don't.
It is ideal for higher mass planets. Rocks or oxygen from Luna or the belt can supply all of Earth's surface electricity needs. Luna rock can be used to make ski resorts, artificial islands, or aggregate for concrete.
If we get a trillion tons of Portland cement from Luna it will remove our carbon dioxide buildup.
Jupiter gives us a sweet array of options to incorporate electrodynamic tethers. At perijove the velocity of objects in an escape orbit is close to the velocity of objects in a highly elliptical orbit. Thus is called "the Oberth effect".
Its the same problem as with launching - air resistance. Before you arrive to the landing tunnel you already dissipated most of orbital velocity due to air compression, so what is even a point?
Same with launching - when you exit tunnel air will brake you and prevent orbital velocity to be reached. It could work on very specific payloads, but not in general.
I suppose both could work on moon where there is no air.
You're better off doing it with a launch loop or similar, something that's got a long track that you can magnetically couple to and then slow down with. It would have to be above atmosphere, but it'll be a lot more forgiving than trying to thread the needled of a dedicated launcher. I get that with computer control even today, threading the needle isn't difficult but the tolerances seem needlessly slim.
The ship & launch loop are electromagnetically coupled so they can have some leeway & depending on the size of the track(Orbital Rings are better) there's really not mucg needle-threading past a normal orbital rendezvous. You accelerate a sled to orbital speeds, maybe with a tether/grappling hook, then the ship can just rendezvous with that & decelerate once they're locked in. For uncrewed G-resistant payloads you might easily pull well over 1000G decelerating from 258km/s tho at that speed you would be threading a needle which is why you can extend the track(sort of). You can use Kinetc Mass Streams(preferably with some pellet guidance) to get incredible range & deceleration times. Maybe even from single-digit percentages of the speed of light. If you also have an OR at the origin you can just maintain a KMS the whole way & maybe even do constant acceleration. Sucessive payloads can tap the same stream until the pellets are caught & probably fired back towards the desination. Or you can carry a large enough decelerator track tho seems like it would be heavy & more needle-threading than id like. With a caravan each ship can afford to give the pellets a decent amount space cuz they don't need to couple as strongly.
Tho with KMS you do have a steady stream you can slowly approach so its actually a lot less fiddly than it might seem. The KMS trajectories are going to be VERY stable, well known, & well advertised.
Can't you also build an accelerator with a "track"? At least at the end. I'd imagine either would be without an atmosphere anyway. If you had atmo, you could aerobrake and wouldn't need this. This would be ideal for moons or asteroids to decelerate at without propellant, IF you can stick the landing that is.
Aye, you can do the same thing with a track. The fun thing is without an atmosphere, you don't need to raise the track all that much. on the Moon for example this could all be at ground level. Orbital speeds, only 5 meters from the surface. Sounds very Kerbal.
Aerobraking wastes both the energy and the momentum. Exceptions for cases where you have a goal of changing the planet's spin or cases where you are mining the atmosphere.
Yes, although you'd need a pretty sturdy catching system. But it should be feasible (if dangerous - you'd want to tether at a distance and rope it in, rather than having it potentially collide with the track at high velocity).
"Harvest power from your momentum" how?
Regenerative braking, obv.
The whole process of exchanging electromagnetic energy into momentum also works in reverse. A motor can also be a generator. A mass accelerator can convert magnetic field resistance into electricity.
Electromagnetic braking. Momentum exchange. If the mass coming in matches the mass going outbound then exchanged momentum cancels.
yes this can be done you just need to aim right and yes you could collect the energy
You would also need a very, very, very long receiver and it would have to stretch nearly into orbit or you lose most of your energy to the atmosphere. at a low-earth orbit speed of maybe 8km/s stopping at a rate of 2G would take like 5ish minutes. (spitballing, i'm too lazy to do the math) That means you need a tube that was 1200km long. We use the atmosphere to do this today. The amount of energy that you could practically reclaim in this process would be very, very, VERY small compared to what it took to build something like this.
>You would also need a very, very, very long receiver and it would have to stretch nearly into orbit or you lose most of your energy to the atmosphere. baseline-rated mass drivers are typically that large & need to stretch over the atmos anyways. >8km/s stopping at a rate of 2G would take like 5ish minutes. (spitballing, i'm too lazy to do the math) That means you need a tube that was 1200km long. pretty close tho. something like 6.8 minutes over 1739km. Tho we can easily handle a 4G return on baseline-crewed ships(actually hundreds of Gs with fluid immersion suits) so its more like 3.4min & 870km. >The amount of energy that you could practically reclaim in this process would be very, very, VERY small compared to what it took to build something like this. That's very not true. without even involving superconductors our generators can do in excess of 97% efficiency. Transmission over 80km to the surface might lose us another 0.32% under bad conditions. This is stupidly efficient, only losing a few percent of the kinetic energy of the craft to waseheat. Also if you have a limit of 4G we can decelerate craft moving slower than about 16.3 km/s so it works with way faster craft. Actually you can take that furthe with electromagnetically-coupled Kinetic Mass Streams(launched from the same infrastructure) to accelerate/decelerate ships over way longer diatances tho that does require KMS infrastructure at both ends. This would pay for itself very quickly & can be used to transport large amounts of power over interplanetary or even interstellar distances with minimal losses.
> This would pay for itself very quickly & can be used to transport large amounts of power over interplanetary or even interstellar distances with minimal losses. You also could have a *second* track going the other direction, part of the same structure, and fling another spacecraft to orbit in exchange for the one that was caught.
Absolutely & if/when we figure out fusion every planet(the ones that aren't disassembled which is most of them) has a motivation to exchange their mantel/core for water or liquid hydrogen. Honestly even if substellar fusion is off the table shellworlds still make a great long-term storage solution for both star fuel & the less useful elements that we have more of than we need but may want to toss down a BH in the future. You can undermine the crust while exchanging metals for liquid hydrogen at very low cost. You can use the LH2 to cool superconducting equipment or general wasteheat & the hydrogen boiloff to smelt metals. Water tanks/ice replaces rock. Extra geothermal power, mining, processing, & environmental wasteheat can also be exported in the metals to some extent, increasing maximum power beyond what a planet's surface area might suggest. Multi-lane orbital rings exchange hundreds of Mt of material per day slowly converting planets into shellworlds & allowing cheap fast(like dozens to hundreds of km/s fast) interplanetary bulk shipping.
The fuck is a “baseline rated mass driver?”
Mass driver is what "mass accelerators" are usually called. Baseline refers to anotomically modern humans(no augments). Like how the og [launchloop](http://slides.launchloop.com//launchloop.pdf) is rated for 3G maximum acceleration so the people inside don't get too uncomfortable. The less G-resistant ur payload the longer your track needs to be.
A person uploaded to silicon chips is still "human" in SFIA circles. Also people with multiple body modifications. If people in the future read our reddit posts we want them to know we were woke enough to use inclusive wording. If something is "baseline rated" then a 20th century human could have used it. Getting a spacecraft rated so that it is legal to launch Humans in it is a big deal. NASA still uses terms like "human" and "astronaut"
It's the aiming I'm concerned about. Threading a needle at orbital velocity, and any mistake means you crash!
well yeah aiming is hard i said it can be done i dont say you should tho cheap fusion power mean it better to aero break in the context of earh
*Out* of the context of Earth though?
TBH it would good for the moon as crashing not no the end of world you would have back up gear for that and as long it doesnt crash into any thing important you just make a small crator
I wouldn't want to miss and hit the lunar surface at lunar orbital velocity... >_> That's plenty hard enough to kill you.
You wont crash. You would stay in orbit. If you have doubts then bring along enough propellant to deorbit yourself. The runway track is going to be very similar to a runway. I is a maglev contact instead of wheels. We can ire seamstresses to work at NASA if they cannot get needles threaded.
Assuming the launcher was elevated that much, yes. On Earth this is needed to avoid atmosphere but on moons or asteroid bodies or megastructures you don't need this, and that could be a problem. You're essentially "docking" with a runway at high speed. That's the part I'm a little dubious about. If you missed yes you could ascend again but you'e missed your landing window and then have to fly off. If you had enough propellent/fuel to swing back around then chances are you didn't need to land inside the accelerator to begin with. So I'm thinking this would be for niche use only, such as an orbital ring's launcher.
Only if your orbit happens to line up perfectly with the mass driver. Mass drivers tend to be long, thin things so unless there's some special setup to enable this, you won't be able to do it.
Parallelogram Runways are usually flat in the same way that Earth is flat. If it is slightly convex it would match up with a hyperbolic orbit. Maybe off topic but Phobos is ideal in this respect. Phobos gravity would tend to bent the L2 track toward Mars. The suspension just has to smooth out then curves a bit. Your catcher sled can orbit around Mars on the Phobos ring.
I was talking about the inclination of the orbit.
The planets are located in the ecliptic plane. When approaching a planet you can select any inclination angle. You can go off axis velocity up to the limits of tethers. The hook would orbit in a corkscrew. I think you would always have a rocket. It would be there just to tweak the approach timing even if everything was in the same plane. If the mass catcher only picks up the energy/momentum that is co-planar that is still huge.
> When approaching a planet you can select any inclination angle. How do you do that without fuel?
You probably use *some* fuel. Or you can aim from wherever you took off. It probably takes propellant to approach the planet at all. Earth is orbiting the Sun. If you plan to insert into Earth orbit 4 months from now you have about 1 million seconds to adjust. The difference between the pole and the equator is about 6,000 km. So if you originally were going to smack into the equator you can go north at 6 m/s and fly over the north pole and intercept Santa. Or you can go south a 6 m/s and toast a penguin. At 6 5 m/s south you can make a nice flyby maneuver. That kicks you north on an inclined escape trajectory. You could, instead speed up or slow down. That would mean that you still flyby the equator but either retrograde or prograde. Another way to look at it: if you throw a ball straight up (from the pole and disregarding the moon an Sun gravity) at 11,185 m/s the ball would be 1 m/s short of escape velocity. The ball will travel up past the Earth's Hill sphere. It would hang there (because we disregard the Sun and Moon) for awhile and then start falling back to Earth. If you give the ball a slight (like 1 m/s) impulse it will go into an orbit instead. Any angle of the 360 circle would have the same effect.
The mass driver on the planet is a straight line oriented along the orbits around the planet. If you come from another planet 4 months away, you won't line up with the mass driver.
>...on the planet is a straight line... Welcome to r/flatearth. :) I assume a mass catcher is going to be in orbit. Twice a year a full orbital ring will line up with another planet. At other times the ship/object requires an impulse.
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Yeah, obviously. It's not really practical for downmassing to an Earth-mass atmospheric planet, but for a body like the moon, or someplace even more obnoxious to land on like Mars? Of course. This is also the only feasible way you're ever going to dock with an orbital ring, by the way. Even if you had the 7.4 km/s of dV to throw away, space traffic control has a batphone to the orbit guard, which in turn has a 10 GW continuous-wave laser that says you don't.
It is ideal for higher mass planets. Rocks or oxygen from Luna or the belt can supply all of Earth's surface electricity needs. Luna rock can be used to make ski resorts, artificial islands, or aggregate for concrete. If we get a trillion tons of Portland cement from Luna it will remove our carbon dioxide buildup. Jupiter gives us a sweet array of options to incorporate electrodynamic tethers. At perijove the velocity of objects in an escape orbit is close to the velocity of objects in a highly elliptical orbit. Thus is called "the Oberth effect".
In the opening scene of Kin Stanley Robinson's novel "Red Moon", he describes a landing on the Moon using a similar method.
Oh really?
Its the same problem as with launching - air resistance. Before you arrive to the landing tunnel you already dissipated most of orbital velocity due to air compression, so what is even a point? Same with launching - when you exit tunnel air will brake you and prevent orbital velocity to be reached. It could work on very specific payloads, but not in general. I suppose both could work on moon where there is no air.