Magnetic forces follow the inverse cube law. So, a magnet is 8 times weaker at 2 times the distance.
This means that over long distances (Of more then a few centimeters), magnetism is incredibly weak. So, you can build a maglev train that hovers a few centimeters above the track, but you can't pull a rocket that's a few meters over the landing pad into place.
Unless the rocket is moving upwards along a tallish launch tower. There you could impart a large force for a few seconds (linear magnets in vertical strip). Nasa studied it but i think the concept produced too many complications. Strapping on another SRB kerbal-style is much easier.
You also have to carry the weight of the corresponding track to at least a couple thousand feet to jettison it safely I bet. It's also at the point where the rocket is at it3 heaviest so the assistance it could give would be really limited.
I think you'd have much better luck turning the rocket into some kind of a sabot round and spending a week compressing a bunch of air into huge tanks and launching it that way. That's how subs launch ICBMs.
The reason that's not done is that rockets aren't reliable enough yet and nobody wants to bet their billion dollar cargo on the engines starting the first time, every time. If you lose every 100th ICBM it's a bummer, but it doesn't make MAD not happen.
For non-human spaceflight, a 1% loss is an option. Insurance ussually assumes a 5ish percent chance that the payload wont survive and another 5ish that it wont be delivered into the ideal orbit.
Electromagnets are big and heavy, and then you have to power them, which is usually more "big and heavy". "Big and Heavy" are the enemies of modern rocketry.
I suspect your parent is suggesting on the platform rather than the rocket. I'm not arguing whether or not it's a good idea, but that should shift a large part of the "big and heavy" issue off of the rocket.
That's a good point, and lets assumes that you can rig the rocket's legs for that without adding any weight. The issues I can imagine would be that you wouldn't get much help very far from the pad, given how quickly the EM force drops off with distance. Even worse, in those last crucial instants, instead of only having to calculate in relation to gravity, now you have to consider the rapidly increasing electromagnetic force. I'm wondering if you'd just rip any realistic feet off the lander?
Either way, it seems more like adding complexity, than a safety net. The really hard part isn't the last foot, it's getting it into that position.
I thought about that, but I wondered If the landing pad was the magnet and the rocket itself wasn't? (I literally have no idea wtf I'm talking about to be clear)
They have pulled it off several times now without the additional complication so I assume it is just not worth the effort. Also what does an electromagnet capable of holding up a rocket require in power?
Would the barge still be agile enough to function? Would the benefits outweigh the additional complication? The absence of such a system on the SpaceX barges suggests the answer to those questions is no.
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Pardon ignorance - why doesn't SpaceX and co use electromagnets to stick the landing of a rocket (in either polarity it seems interesting)?
Magnetic forces follow the inverse cube law. So, a magnet is 8 times weaker at 2 times the distance.
This means that over long distances (Of more then a few centimeters), magnetism is incredibly weak. So, you can build a maglev train that hovers a few centimeters above the track, but you can't pull a rocket that's a few meters over the landing pad into place.
Unless the rocket is moving upwards along a tallish launch tower. There you could impart a large force for a few seconds (linear magnets in vertical strip). Nasa studied it but i think the concept produced too many complications. Strapping on another SRB kerbal-style is much easier.
You also have to carry the weight of the corresponding track to at least a couple thousand feet to jettison it safely I bet. It's also at the point where the rocket is at it3 heaviest so the assistance it could give would be really limited.
I think you'd have much better luck turning the rocket into some kind of a sabot round and spending a week compressing a bunch of air into huge tanks and launching it that way. That's how subs launch ICBMs.
The reason that's not done is that rockets aren't reliable enough yet and nobody wants to bet their billion dollar cargo on the engines starting the first time, every time. If you lose every 100th ICBM it's a bummer, but it doesn't make MAD not happen.
https://www.youtube.com/watch?v=1aPvGGvnAGQ
For non-human spaceflight, a 1% loss is an option. Insurance ussually assumes a 5ish percent chance that the payload wont survive and another 5ish that it wont be delivered into the ideal orbit.
never mind the actual sums involved, 1% on top of 10% is a 10% increase in coverage. Is coverage inclusive of the time lost in labor as well?
Makes sense. Thanks! :)
Electromagnets are big and heavy, and then you have to power them, which is usually more "big and heavy". "Big and Heavy" are the enemies of modern rocketry.
I suspect your parent is suggesting on the platform rather than the rocket. I'm not arguing whether or not it's a good idea, but that should shift a large part of the "big and heavy" issue off of the rocket.
That's a good point, and lets assumes that you can rig the rocket's legs for that without adding any weight. The issues I can imagine would be that you wouldn't get much help very far from the pad, given how quickly the EM force drops off with distance. Even worse, in those last crucial instants, instead of only having to calculate in relation to gravity, now you have to consider the rapidly increasing electromagnetic force. I'm wondering if you'd just rip any realistic feet off the lander?
Either way, it seems more like adding complexity, than a safety net. The really hard part isn't the last foot, it's getting it into that position.
I thought about that, but I wondered If the landing pad was the magnet and the rocket itself wasn't? (I literally have no idea wtf I'm talking about to be clear)
They have pulled it off several times now without the additional complication so I assume it is just not worth the effort. Also what does an electromagnet capable of holding up a rocket require in power?
Would the barge still be agile enough to function? Would the benefits outweigh the additional complication? The absence of such a system on the SpaceX barges suggests the answer to those questions is no.
Couldn't do that on another planet without installing them first. They want their system to be usable everywhere.
lol, this is the actual right answer. Cleaver, thank you.