Turning anti-missile missile into space-to-space missile

Dilandu

Dilandu

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A question: how hard would be to adapt an Earth-based anti-missile missile (like SM-3 or THAAD) to work as space-to-space missile on a spacecraft?

To elaborate why I need it: I'm working out details for a sci-fi story, set in late XXI century. The humanity found itself in a situation of space war against space-based rebellion of sentient AI's. Granted, it's not exactly a very high-stake war; neither side have any intention to destroy or even enslave the other. Basically the whole conflict is caused by disagreements about AI's rights in human society, and probably could be solved peacefully, if not for some dumb ideas from both sides (on human side, there were religious nuts screaming "ANTICHRIST COMING!!!" and greedy megacorps throwing a fit "paying AI for its job?! What next, raising minimal wage for human workers?!" - on machine sid,e there were statistically based pattern-thinking "well, historically humans often fought a wars over their rights, so it seems staring one is statistically good idea")

The Earth problem is, that spacefaring nations weren't exactly prepared to a real space warfare. The most they got before shooting started was missile defense sattelites on low orbit and some patrol spacecraft, armed with "remote inspector drones" (ostensibly only for peaceful inspections, but also capable of "accidental" ramming...). Not much, and most of what they have was sabotaged by AI's through pre-planed backdoors anyway. The Earth was essentially put into space blockade - causing massive inconveniences, since all major economics already became dependent of space internet, beamed space power, asteroid mining, ect.

To solve the crisis, Earth nations started to build spacefleet from scratch, relying on off-the-shelf components. And since the dedicated space-to-space missiles are in very short supply, they decided to remedy the problem by re-purposing a massive stockpiles of anti-ballistic missiles available. Essentially I'm talking about direct decendants of SM-3, THAAD, Arrow-3, S-500 and similar modern systems.

My question, therefore: how hard it would be to refit, say, an SM-3 Block II missile into space-to-space weapon?

*Obviously, there is no need to have booster in space;

* Control fins on first stage must be replaced with RCS engines (probably in form of strap-on modules put around missile body;

* Since missile is not designed survive constant heating-cooling cycles and prolonged vacuum on Earth orbit, it must be put into climate-controlled launch container, filled with nitrogen;

* The interceptor would likely require additional power supply/cooling for prolonged cruising toward the target (after all, space is big);

What else would be required? My concerns is mainly about zero-g conditions; wouldn't they affect the density of solid fuel grain (after all, the rocket engine was not designed for freefall!). But I kinda could miss something else.
 
Dilandu said:
A question: how hard would be to adapt an Earth-based anti-missile missile (like SM-3 or THAAD) to work as space-to-space missile on a spacecraft?

To elaborate why I need it: I'm working out details for a sci-fi story, set in late XXI century. The humanity found itself in a situation of space war against space-based rebellion of sentient AI's. Granted, it's not exactly a very high-stake war; neither side have any intention to destroy or even enslave the other. Basically the whole conflict is caused by disagreements about AI's rights in human society, and probably could be solved peacefully, if not for some dumb ideas from both sides (on human side, there were religious nuts screaming "ANTICHRIST COMING!!!" and greedy megacorps throwing a fit "paying AI for its job?! What next, raising minimal wage for human workers?!" - on machine sid,e there were statistically based pattern-thinking "well, historically humans often fought a wars over their rights, so it seems staring one is statistically good idea")

The Earth problem is, that spacefaring nations weren't exactly prepared to a real space warfare. The most they got before shooting started was missile defense sattelites on low orbit and some patrol spacecraft, armed with "remote inspector drones" (ostensibly only for peaceful inspections, but also capable of "accidental" ramming...). Not much, and most of what they have was sabotaged by AI's through pre-planed backdoors anyway. The Earth was essentially put into space blockade - causing massive inconveniences, since all major economics already became dependent of space internet, beamed space power, asteroid mining, ect.

To solve the crisis, Earth nations started to build spacefleet from scratch, relying on off-the-shelf components. And since the dedicated space-to-space missiles are in very short supply, they decided to remedy the problem by re-purposing a massive stockpiles of anti-ballistic missiles available. Essentially I'm talking about direct decendants of SM-3, THAAD, Arrow-3, S-500 and similar modern systems.

My question, therefore: how hard it would be to refit, say, an SM-3 Block II missile into space-to-space weapon?

*Obviously, there is no need to have booster in space;

* Control fins on first stage must be replaced with RCS engines (probably in form of strap-on modules put around missile body;

* Since missile is not designed survive constant heating-cooling cycles and prolonged vacuum on Earth orbit, it must be put into climate-controlled launch container, filled with nitrogen;

* The interceptor would likely require additional power supply/cooling for prolonged cruising toward the target (after all, space is big);

What else would be required? My concerns is mainly about zero-g conditions; wouldn't they affect the density of solid fuel grain (after all, the rocket engine was not designed for freefall!). But I kinda could miss something else.
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Aerodynamic bodies designed to fly in the atmosphere are not suitable for effective maneuvering in a vacuum. An elongated body needs to use four vernier-type orientation motors at the front and another four at the rear. Something of lesser length, even spherical, would maneuver better with the center of gravity aligned with the intersection of six verniers. It is not necessary to install a warhead, a kinetic impact will suffice, if the accuracy of the radar or infrared guidance system is adequate.
 
Justo Miranda said:
It is not necessary to install a warhead, a kinetic impact will suffice, if the accuracy of the radar or infrared guidance system is adequate.
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Yep, and since the missiles I proposed to use already have kinetic kill vehicles, then it would require less efforts. A point about elongated body in vacuum is valid, true.
 
PAM-D…the next generation…

I understand the real reason nukes went to conical designs was because folks couldn’t tell the Fat Man types from the solids:

You sure that’s the nuke Billy-Bob? That looks like a nozzle!”

“Nah—that’s just the cone of shame from the flea dip.”

As it happened, Billy was right and neither he, his friend, nor their atoll were ever seen again.
 
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Dilandu said:
Control fins on first stage must be replaced with RCS engines (probably in form of strap-on modules put around missile body;
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Replace the motor completely. Need variable impulse liquid system and thrust vector control is easier with liquid and RCS would not be needed.
Dilandu said:
Since missile is not designed survive constant heating-cooling cycles and prolonged vacuum on Earth orbit, it must be put into climate-controlled launch container, filled with nitrogen;
Click to expand...
What is the nitrogen for
Dilandu said:
the interceptor would likely require additional power supply/cooling for prolonged cruising toward the target (after all, space is big);
Click to expand...
Need new avionics that vacuum rated

Dilandu said:
What else would be required? My concerns is mainly about zero-g conditions; wouldn't they affect the density of solid fuel grain (after all, the rocket engine was not designed for freefall!). But I kinda could miss something else.
Click to expand...
zero-g has no effect
 
Justo Miranda said:
Aerodynamic bodies designed to fly in the atmosphere are not suitable for effective maneuvering in a vacuum. An elongated body needs to use four vernier-type orientation motors at the front and another four at the rear. Something of lesser length, even spherical, would maneuver better with the center of gravity aligned with the intersection of six verniers. It is not necessary to install a warhead, a kinetic impact will suffice, if the accuracy of the radar or infrared guidance system is adequate.
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Just need 4 divert thrusters located near the CG and 4 attitude thrusters at either end.
 
Byeman said:
Replace the motor completely. Need variable impulse liquid system and thrust vector control is easier with liquid and RCS would not be needed.
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True, but I was thinking about using existing hardware as much as possible... But seems it would not be practical.

Byeman said:
What is the nitrogen for
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To maintain positive pressure & thremal regulation around missile while its stored.

Byeman said:
Need new avionics that vacuum rated
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Interceptor itself is vacuum-rated - the anti-ballistic is designed to intercept above Earth atmosphere anyway.
 
Dilandu said:
To maintain positive pressure & thremal regulation around missile while its stored.
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no need for the pressure for storage.

Dilandu said:
Interceptor itself is vacuum-rated - the anti-ballistic is designed to intercept above Earth atmosphere anyway.
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That is for a short duration and thermal mass can be used to handle loads.

A pressurized container is mass and complexity.
 
Seal the nozzles prevent Vacuum outgassing of the solid rockets.
during ignition the seal breaks by gas pressure and heat

You have to aim the Missile on target and fire, stage I to 3 accelerate on target
while stage 4 use it control system to aim on approaching target
 
You will need thrust vectoring for all stages that don't already rely on it. That may or may not be as simple as a direct module swap - same volume, similar weights.

You will need to completely re-do the interface between guidance and steering, either in hardware or software or both, in the lower stages to compensate for the fact that they aren't flying in atmosphere any more - the missile has to be 'taught' to do different things to get the same steering output in response to guidance commands. The alternative is to risk unstable system outputs in response to the same guidance inputs with missiles going out of control.

You can leave the wings on to keep things simple, but a developed version will probably have them removed/never fitted.

Control system reprogramming needs to account for any and all changes in centre of gravity related to the motor substitutions.
 
pathology_doc said:
The alternative is to redesign the missile with side and roll thrusters. TVC holds out the possibility of modular swap-out of the motors.
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Not really
Side and roll thrusters are going to be required regardless.
pathology_doc said:
How quickly do you want this thing in service?
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Do you want the missile to hit the target or not?
 
Byeman said:
Not really
Side and roll thrusters are going to be required regardless.

Do you want the missile to hit the target or not?
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1) Roll-yaw coupling isn't a thing in a vacuum. If you have a nozzle that can swing around the entire arc, roll becomes irrelevant.

2) Can't hit the target if it's not in service.
 
pathology_doc said:
1) Roll-yaw coupling isn't a thing in a vacuum. If you have a nozzle that can swing around the entire arc, roll becomes irrelevant.
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A meaningless point.
Thrust vectoring is useless without a motor producing thrust.
Most of the flight is coasting and not under thrust
Divert and attitude control thrusters are needed up to the moment of impact.
Pointing sensors at the target is required at all times.
This isn't atmospheric flight. Much of the delta V required isn't going be in the direction of flight.
So how is a system that uses thrust vectoring to produce divert thrust going to keep the sensors pointed at the target?
What articulating sensors are on missiles now?

How quickly do you want this thing in service now? Develop divert and attitude control thruster packages or articulating sensor pods?
 
Byeman said:
Thrust vectoring is useless without a motor producing thrust.
Most of the flight is coasting and not under thrust
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An inaccurate assumption, in my opinion. The missile will probably run boost-sustain or boost-coast-relight with the terminal phase under power for maximum acceleration available at the moment of impact.
 
pathology_doc said:
An inaccurate assumption, in my opinion. The missile will probably run boost-sustain or boost-coast-relight with the terminal phase under power for maximum acceleration available at the moment of impact.
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Not with existing motors.
How quickly do you want this thing in service?

But the rest of my points are more relevant then. Going to need an articulating pod to keep sensors on target while the missile rotates away from the target to produce divert velocity.
 
THAAD canisters are sealed-self contained and purged with nitrogen to prevent oxidation and corrosion. Also, protects against accidental leaks of the hypergolics.

You would absolutely need a thermal management system.

Another obstacle regarding the canister is how a space launch managed vs a ground based launch is managed. The interceptor breaks through the dome of the canister. How is the space based platform stablized for and during egress?

But, these are interceptors without a warhead. Are they being repurposed to be tactical precision fires?
 
In space all objects automatically start to rotate at some point. It's a natural law (forgot the name).
Stabillity has to be done with the usual balistic rotation.
In the case of long range, shifting a mass could be used for steering without the need of RCS & fuel. I'm not sure whether the mass & mechanical motor tradeoff is adventageous enough for "smaller" missiles. It's also likely not nimble enough for terminal steering.
 
Seragina said:
In space all objects automatically start to rotate at some point. It's a natural law (forgot the name).
Stabillity has to be done with the usual balistic rotation.
In the case of long range, shifting a mass could be used for steering without the need of RCS & fuel. I'm not sure whether the mass & mechanical motor tradeoff is adventageous enough for "smaller" missiles. It's also likely not nimble enough for terminal steering.
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Or you have a couple of gyroscopes installed. And by braking or accelerating them you can make small pointing changes.
 
Scott Kenny said:
Or you have a couple of gyroscopes installed. And by braking or accelerating them you can make small pointing changes.
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I'm not a fan of flywheel steering as it needs ramp/spin up time, continous powering and the energy-return/breaking is not constant.
While a mass can simple move along the diameter line and take advantage of the auto-spin. The mechanical control would be similar to a helicopter's cyclic steering.

Flywheel and steering-based vehicle dynamics enhancement methods
 

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