Writing: Input Wanted Limits of detection and interception in space

[GTOM]

I write about a world, where Moon fight against Mars, and there is a postapocalyptic Earth. Can it be realistically justified, that mine metals on asteroid belt and transfer them to Moon isnt much more expensive than lift them from Earth?

Pro : Crates can be launched electromagnetically from asteroids, no need for expensive rockets.
Con : Isnt it just as easy for Mars to intercept those crates?

Question : if a crate doesnt emit much heat after launch, and not many kilometers big like a comet, can the martians calculate its exact trajectory and hit it with a simple missile? (If ships arent nearby.)

What could be cheap countermeasures? Use decoys? (Empty crates.) Attach ion thrusters to crates, just a few km/s deltaV and low acceleration is fine to make the course unpredictable? Automated defence systems? Since in my world Earth is ruined due to rebel AI, no strong AIs.

 

[.Scott]

There would be at least two significant advantages in having Lunar enterprises source minerals from the asteroid belt rather than Earth.
1) The specific impulse required of the rocket system would be much smaller. In fact, given enough patience, solar-powered ion thrusters could be used.
2) Many of the minerals are likely to be more easily collected from asteroids.

Regarding the intercept: The best trajectory from the asteroid belt to Earth and Moon would give you a good starting point in search of these cargo ships. And, if ion thrusters are used, they would be active during a large portion of the cargo's path. An active ion thruster system will have emissions that can likely be detected by telescopes on or near Mars. And Mars could deploy satellites with telescopes and missiles to orbit near the asteroid belt (about the Martian orbit) to get an early detection and possible kill of these cargo treks. Although noble gases are generally used for electrostatic ion thrusters, a large commercial operation ferrying heavy patient loads (ie, no human passengers) might find some other element more economical - such as iron or carbon. In any case, such engines would have signature emission bands that would make them easy to identify.

The intercept itself should pose no technological problem - especially if the cargo ship keeps it thrusters running. It's path will be very predictable and with due planning, delivery of the effector should be very reliable against such a massive target.

It is also possible for a missile to hi-jack a shipment - by rendezvous and then redirecting the cargo propulsion system. If this is done, team Mars might arrange for the shipments to crash into preselected regions of Mars for their own eventual use.

 

[GTOM]

There would be at least two significant advantages in having Lunar enterprises source minerals from the asteroid belt rather than Earth.
1) The specific impulse required of the rocket system would be much smaller. In fact, given enough patience, solar-powered ion thrusters could be used.
2) Many of the minerals are likely to be more easily collected from asteroids.

Regarding the intercept: The best trajectory from the asteroid belt to Earth and Moon would give you a good starting point in search of these cargo ships. And, if ion thrusters are used, they would be active during a large portion of the cargo's path. An active ion thruster system will have emissions that can likely be detected by telescopes on or near Mars. And Mars could deploy satellites with telescopes and missiles to orbit near the asteroid belt (about the Martian orbit) to get an early detection and possible kill of these cargo treks. Although noble gases are generally used for electrostatic ion thrusters, a large commercial operation ferrying heavy patient loads (ie, no human passengers) might find some other element more economical - such as iron or carbon. In any case, such engines would have signature emission bands that would make them easy to identify.

The intercept itself should pose no technological problem - especially if the cargo ship keeps it thrusters running. It's path will be very predictable and with due planning, delivery of the effector should be very reliable against such a massive target.

It is also possible for a missile to hi-jack a shipment - by rendezvous and then redirecting the cargo propulsion system. If this is done, team Mars might arrange for the shipments to crash into preselected regions of Mars for their own eventual use.

So you advocate piracy. Although i think that rather requires ships. With all theese difficulties, is it still reasonable that mine on Earth isnt cheaper?
(Well they have to face attacks on Earth too, but rather from guerillas.)

 

[.Scott]

What is cheaper depends on what you want and how much of it you want.
In most cases, the best source of minerals for Lunar enterprises will be the moon.
If it's only several hundred tons of something that is cheap on Earth and rare on the moon (say bananas), then have Elon move it for you. But if you are looking for a mineral that's rare on the moon, then it's likely rare on Earth as well. And if you need thousands of tons of it, that will likely strain your post-apocalyptic space-faring infrastructure.

I don't imagine that either the "missiles" or the cargo vessels are going to be manned. In most cases, once intercepted, "taking" the cargo without the vessel would present problems. So, I think that "hijacking" rather than "piracy" would be the first tactic.

But there are some inherent problems for the Mars colony. Failing to control the cargo would leave it in an orbit that would "visit" Mars now and then - presenting a hazard to that planet. Striking the cargo for the purpose of shattering it would ultimately result in intense Martian meteor showers - a planet where such meteors often make it to the surface with lethal force.

Deliberate countermeasure that could be employed by the Lunatics (or whatever you call your Moon dwellers) might be to deliberately destroy the ion thrusters when a cargo vessel was high-jacked. Or, worse yet, hide a secondary ion thruster robot in the cargo that could be deployed after the hijacking to deliberately create a Martian hazard. So, an attempted theft might follow this line: Mars intercepts the cargo with a robot, disconnects the cargo thrusters from cargo navigation, then directs the cargo to a safe crash site on Mars. Moon waits for the cargo to approach Mars; destroys it primary hijacked thrusters remotely; engages the secondary thrusters; and directs the payload into the Martian capital.

 

[GTOM]

What is cheaper depends on what you want and how much of it you want.
In most cases, the best source of minerals for Lunar enterprises will be the moon.
If it's only several hundred tons of something that is cheap on Earth and rare on the moon (say bananas), then have Elon move it for you. But if you are looking for a mineral that's rare on the moon, then it's likely rare on Earth as well. And if you need thousands of tons of it, that will likely strain your post-apocalyptic space-faring infrastructure.

I don't imagine that either the "missiles" or the cargo vessels are going to be manned. In most cases, once intercepted, "taking" the cargo without the vessel would present problems. So, I think that "hijacking" rather than "piracy" would be the first tactic.

But there are some inherent problems for the Mars colony. Failing to control the cargo would leave it in an orbit that would "visit" Mars now and then - presenting a hazard to that planet. Striking the cargo for the purpose of shattering it would ultimately result in intense Martian meteor showers - a planet where such meteors often make it to the surface with lethal force.

Deliberate countermeasure that could be employed by the Lunatics (or whatever you call your Moon dwellers) might be to deliberately destroy the ion thrusters when a cargo vessel was high-jacked. Or, worse yet, hide a secondary ion thruster robot in the cargo that could be deployed after the hijacking to deliberately create a Martian hazard. So, an attempted theft might follow this line: Mars intercepts the cargo with a robot, disconnects the cargo thrusters from cargo navigation, then directs the cargo to a safe crash site on Mars. Moon waits for the cargo to approach Mars; destroys it primary hijacked thrusters remotely; engages the secondary thrusters; and directs the payload into the Martian capital.

i think such dirty tricks are good justification that redirect cargo should be trusted to manned ships (together with no strong AI).

 

[.Scott]

Th Martin orbit is just inside the asteroid belt. The best place to launch an interceptor is the same region that the miners will be launching their cargo treks. That location near the Martian orbital path, but will lead the Earth in its orbit. So there will be many mining sites and many pre-positioned interceptor stations. Those stations will remain dormant for a couple of years before things line up and it's their turn for action. Then the cargo will launch, the pre-positioned station will detect the ion thruster, and the station will launch an interceptor. If the mining is manned, then it would makes sense to have the cargo ship manned. The crew would have arrived at their mining location about two years earlier, and now they are returning home with their cargo.

But should the missile be manned? The main purpose of the missile is to intercept the cargo and make sure that it never reaches the moon. As a secondary mission, it may want to keep the Martian orbit from becoming too littered. But it needs to be fast and maneuverable at the expense of being disposable. If you put people on it, they will be likewise disposable. The intercept stations themselves might be manned, but it would be a rough assignment. The crew would be alone for years and and every other year they get to attack. So, I would guess they would be unmanned - stealthy outposts trying to look like (unminable) asteroids.
So, you have a very slow cargo vessel that could be manned - but to what purpose? It might serve as the cheapest ride home - but recruitment for the mining mission would be a lot easier if a speedier craft designed to ferry people was used.

Spoofing a cargo vessel is possible. You would mask the "exhaust" of the real cargo while using unmasked lighter ion thrusters for the "empty boxes". Of course, your phony cargo vessels will need to be cheaper for the Lunatics to make than the missiles are for the Martians.
A counter measure to that would be to attempt the intercept much closer to the Moon - after getting a longer look at the decoys. And if the intercept is delayed long enough, the apogee of the cargo will be well below the Martian orbit and no longer any Martian hazard.
On the other hand, the close to the Moon you get, the closer to the Lunar defenses you get.

 

[DaveC426913]

I think the biggest problem here (so big you may have to ignore it) involves the vast distances - and variations in distances - between cargo, intended target and redirected target.

In a space of a mere six months, the distance between Moon and Mars can vary by 400% (100Mkm to 400Mkm), and every time it will be a completely different profile. In fact, the fuel/time costs would vary so widely that essentially it would be a case of intercept windows opening and slamming shut. i.e. times when the intercept is just too expensive to garner any profit from the attempt.

Not only that but orbital mechanics are open source: equal opportunity to friend and foe alike.

The Lunatics will be just as aware of these windows as the Areians. In other words, the Lunatics will know to a good degree of accuracy where and when their shipments are safe, as well as where and when they are most likely to be intercepted.

 

[GTOM]

Th Martin orbit is just inside the asteroid belt. The best place to launch an interceptor is the same region that the miners will be launching their cargo treks. That location near the Martian orbital path, but will lead the Earth in its orbit. So there will be many mining sites and many pre-positioned interceptor stations. Those stations will remain dormant for a couple of years before things line up and it's their turn for action. Then the cargo will launch, the pre-positioned station will detect the ion thruster, and the station will launch an interceptor. If the mining is manned, then it would makes sense to have the cargo ship manned. The crew would have arrived at their mining location about two years earlier, and now they are returning home with their cargo.

But should the missile be manned? The main purpose of the missile is to intercept the cargo and make sure that it never reaches the moon. As a secondary mission, it may want to keep the Martian orbit from becoming too littered. But it needs to be fast and maneuverable at the expense of being disposable. If you put people on it, they will be likewise disposable. The intercept stations themselves might be manned, but it would be a rough assignment. The crew would be alone for years and and every other year they get to attack. So, I would guess they would be unmanned - stealthy outposts trying to look like (unminable) asteroids.
So, you have a very slow cargo vessel that could be manned - but to what purpose? It might serve as the cheapest ride home - but recruitment for the mining mission would be a lot easier if a speedier craft designed to ferry people was used.

Spoofing a cargo vessel is possible. You would mask the "exhaust" of the real cargo while using unmasked lighter ion thrusters for the "empty boxes". Of course, your phony cargo vessels will need to be cheaper for the Lunatics to make than the missiles are for the Martians.
A counter measure to that would be to attempt the intercept much closer to the Moon - after getting a longer look at the decoys. And if the intercept is delayed long enough, the apogee of the cargo will be well below the Martian orbit and no longer any Martian hazard.
On the other hand, the close to the Moon you get, the closer to the Lunar defenses you get.

But if catch happens close to belt, they can simply send a missile after redirected cargo. Since cargo wont have big acceleration, it will be hit and reach mars in form of a meteor shower.
A ship that is fast without cargo, can catch it halfway, the crew and its drone fighters can disable security systems. With cargo they are slow too, but if lunar ships arent close enough, they could still make it to a safe martian orbit.

 

[GTOM]

I think the biggest problem here (so big you may have to ignore it) involves the vast distances - and variations in distances - between cargo, intended target and redirected target.

In a space of a mere six months, the distance between Moon and Mars can vary by 400% (100Mkm to 400Mkm), and every time it will be a completely different profile. In fact, the fuel/time costs would vary so widely that essentially it would be a case of intercept windows opening and slamming shut. i.e. times when the intercept is just too expensive to garner any profit from the attempt.

Not only that but orbital mechanics are open source: equal opportunity to friend and foe alike.

The Lunatics will be just as aware of these windows as the Areians. In other words, the Lunatics will know to a good degree of accuracy where and when their shipments are safe, as well as where and when they are most likely to be intercepted.

I also thought if moon is on one side of the sun and mars is on the other side, that is a safe launch opportunity.
Although Mars could also launch from a few friendly asteroids. From neutral ones too if the ship isnt an obvious warship, but a cargo ship with fighters in bay.

 

[.Scott]

But if catch happens close to belt, they can simply send a missile after redirected cargo. Since cargo wont have big acceleration, it will be hit and reach mars in form of a meteor shower.
A ship that is fast without cargo, can catch it halfway, the crew and its drone fighters can disable security systems. With cargo they are slow too, but if lunar ships arent close enough, they could still make it to a safe martian orbit.

Let me rephrase to be sure I catch what you're saying:
If the Martian craft intercepts the cargo craft and sees it being redirected, the Lunatics can send a missile to scatter their cargo in a way leas favorable to the Martians.
But they could include a remote control explosive in all real cargo vessels as well. It would be simpler.

A Lunatic ship without cargo can catch "it" (the intercepted cargo ship ?) the crew (of the cargo ship, of the fast ship?) can disable security systems (what security systems?). You're using way too many pronouns. I can't even guess at that last statement.

 

[GTOM]

Let me rephrase to be sure I catch what you're saying:
If the Martian craft intercepts the cargo craft and sees it being redirected, the Lunatics can send a missile to scatter their cargo in a way leas favorable to the Martians.
But they could include a remote control explosive in all real cargo vessels as well. It would be simpler.

A Lunatic ship without cargo can catch "it" (the intercepted cargo ship ?) the crew (of the cargo ship, of the fast ship?) can disable security systems (what security systems?). You're using way too many pronouns. I can't even guess at that last statement.

I cant edit it anymore.

So the martians want to capture or destroy cargo. If it is close to belt, only destruction can happen, since either it have a bomb, or the asteroid send missile after it.
Even if martian unmanned interceptor station manage to be stealthy close to belt, it is very hard to get far.

If ship catch up halfway, and cargo is blown, then metal wont just disappear, some part of it can be still retrieved by ship.
Anyway moon gets nothing, and bomb wont go off close to Mars.
Maybe the crew of the ship can find some way to disarm the bomb. Maybe it isnt safe enough to program a bomb to go off if it simply dont get a certain signal.

 

[GTOM]

I wondered about a story option: they say stealth without some magic heat sink is irreal, even if a ship could mask heat radiation in one direction, the enemy can easily scatter lots of small probes in space.
However what if a spy could get the coordinates of the recon probes? They couldnt just relocate them without using thrusters that would reveal them. Wouldnt that mean that stealth attacks would be possible for a while at least?