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Kessler Dome ABM Satellites


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Without any discussion of the current very tragic and very political events happening in Europe...

There have been a lot of proposals for different strategies to intercept a ballistic missile. As a refresher, an intercontinental ballistic missile has four flight phases: the boost phase (while the rocket motor is firing), the coast phase (while the payload is coasting through space), the re-entry phase (where the payload or MIRV punches back through the atmosphere), and the terminal phase (from plasma sheath termination to impact). A hypersonic glide vehicle, like the Avangard design, is able to maneuver in a non-ballistic fashion during the terminal phase, but is otherwise the same as an ordinary ICBM.

The desire to defend against inbound ICBMs lead to the development of many different anti-ballistic missile systems and designs. Typically, each different type of ABM system targets the ICBM in a different phase:

  • Boost phase. During boost phase, the missile is still moving fairly slowly and its carrier rocket is vulnerable to attack. The YAL-1 airborne chemical laser system was designed for this phase, and we have also tested high-acceleration air-to-air missiles, which could be fired from fighter aircraft. The disadvantage of both of those is that you already need the aircraft to be airborne and in the vicinity when the missile launches. The Super-Excalibur nuclear-pumped x-ray laser system also would have targeted the carrier rocket during the boost phase, but it had its own host of problems.
  • Coast phase. As a rule, ICBMs do not maneuver during their coast phase outside of the atmosphere, making them fairly easy to target. They are, however, very small targets. Plus,  if the missile is carrying multiple independent payloads (which is now usually the case), that separation event will happen almost immediately, meaning that you now have multiple targets. The original Excalibur, if it had been built, would have targeted the ICBM at the very beginning of the coast phase. The Spartan ABM missile, launched defensively, would have used a five-megaton physics package to intercept and destroy incoming payloads without requiring a perfect lock on the target. The primary US ABM system, the Ground-Based Midcourse Defense system, uses a maneuvering exoatmospheric kill vehicle to achieve reasonably high probability (>50%) of a direct impact with an oncoming missile while it is still outside of the atmosphere.
  •  Re-entry phase. Although the THAAD system is designed primarily for intermediate-range missiles, it is believed to be capable of intercepting ICBMs with a hit-to-kill approach during this phase, although it requires proximity and upgraded guidance.
  • Terminal phase. An ICBM-launched payload spends less than a minute in the terminal phase, making it extraordinarily difficult to intercept. The only successful system was the Nike Sprint missile, which accelerated at approximately 100 g and carried its own physics package for a proximity interception. It was extraordinarily expensive and difficult.

It is a thorny problem.

But it got me thinking -- what if there was a way to target not ONE missile during the coast phase, but ALL missiles during the coast phase? We all know about the Kessler syndrome, where the breakup of one LEO satellite could create a debris field that threatens other satellites, leading to a chain reaction that makes space inaccessible. What if that basic principle (with modifications) was applied to a coast-phase intercept?

Of course, we don't want to actually trigger Kessler syndrome, no matter how dire the situation may be. So the debris field would need to be at a very low altitude, such that all the debris would burn up and re-enter in a matter of days.

Imagine a spacecraft carrying its very own ready-made debris field: a few thousand pounds of lightweight aluminum plates. Put a few dozen of these into 300x300 km polar orbits with a range of different ascending-node longitudes, but phased such that several are crossing over the Arctic Circle at any given time.

The spacecraft would need to carry enough fuel to lower its orbit into a 100x100 km circular orbit and then raise it back up to 300x300 km, several times. At 300x300 km the stationkeeping cost is reasonably low. In a high-alert situation where the threat of an ICBM seemed likely, all of the spacecraft would lower their orbits down to 100x100 km, where stationkeeping costs are higher. If the threat passed, they would return to 300x300 km.

In the event of a launch, the satellites closest to the North Pole would blow their payloads, releasing clouds of orbital debris. These debris clouds in turn would impact each other, creating an massive dome of debris across the Arctic Circle. That cloud would only be concentrated over the Arctic Circle for a few minutes every other hour, of course, but with enough satellites in place, you could create a dynamic, persistent debris cloud that would last for several days.

The question, I suppose, becomes whether such a cloud would actually have a chance of damaging or impeding an ICBM passing through that region of space.

Or would there be any other way to use a debris cloud approach rather than a "hit-to-kill" approach?

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What stops the enemy from just waiting a week to launch their strike?

Or detonating nuclear weapons in space to "fry" the debris-dispenser sats? Followed by some form of attack on space launch facilities to prevent more from being launched.

Beyond the effectiveness of the concept itself, the myriad of available countermeasures would make it unworkable.

I'm still very interested to see how others might reply though.

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32 minutes ago, SunlitZelkova said:

What stops the enemy from just waiting a week to launch their strike?

Or detonating nuclear weapons in space to "fry" the debris-dispenser sats? Followed by some form of attack on space launch facilities to prevent more from being launched.

Oh, the satellites wouldn't blow their payloads just on a whim. They would only blow their payloads if an actual launch had been detected. If we're at the point where one ICBM has been launched, it's a pretty safe bet that whatever happens subsequently is going to happen pretty fast. It's not like the world powers are going to lob one missile at each other every few days or something. For the same reason, a direct attack on the satellites doesn't work; once an attack has launched, there would be an immediate response and so the satellites would blow on their own before getting hit.

I may have confused the issue by proposing that they would drop down to 100 km in a high-threat situation. Dropping down to a lower altitude "primes" them, but they would have enough stationkeeping propellant to stay there for a while. Obviously, keeping them "primed" for long periods of time reduces the available mission time. 

32 minutes ago, SunlitZelkova said:

Beyond the effectiveness of the concept itself

That's what I'm curious about. Would such a debris cloud actually pose a threat to ICBMs with MIRVs?

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3 hours ago, sevenperforce said:

Would such a debris cloud actually pose a threat to ICBMs with MIRVs

That's the $64,000 question... and I'm of the opinion that 'not likely'.  Big sky, little bullet.

Also: There's a real difference between a stray bolt hitting an unarmored satellite and knocking out a key system, and that same bolt hitting a small, possibly armored/steel&ceramic encased warhead and disabling it.  I'm guessing that most Soviet MIRVs are relatively tough and designed back when folks overdesigned stuff to just make it work.

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A typical US warhead is ~60cm in diameter. Assuming a lofted trajectory, its passing through the 100km orbit twice, and at a high angle, so punching through a sheet of debris. With a cross sectional area of 0.28m2, that cloud needs to be incredibly dense to ensure a hit in 1 pass, only slightly less dense to insure a hit with 2 passes.

Seems like a complete non-starter to me. You'd need a constellation such that they can uniformly deny tiny objects passage, and at incredibly short notice. If you wait until launch, they need to cover the entire orbit over launch areas uniformly in under 2 minutes. Launch, launch detected, double checked, warning sent to decision maker (that should be plural for all this stuff, IMNSHO, 1 person is a Bad Idea™), decision has to be made, tick, tock, tick tock... trigger pulled. Even very optimistically, the devices need to disperse stuff to insure a RV gets clobbered (randomly) in what, a minute? The second pass obviously gives more time, but I'd almost write off the first pass.

I attended a talk about SDI at the physics dept in the 80s, can't remember who gave it, it was someone pretty high up (might have been Teller, I did see him give a talk, can't remember if that was the one). One point that came up was that countermeasures are cheaper than the SDI measure. So for directed energy weapons, spin the rocket so the beam must dwell longer. For KKVs, dummy warheads, etc. Even if such a system knocked out X%, you only need to ensure that a certain % get through. Launch more, more MIRVs, etc.

Course the debris cloud idea avoids the target acquisition problem, which is a plus. A friend of mine (programmer) worked on SDI as well. He couldn't talk about his specific work, but he told me that it was all BS. He said something like, "You could give me satellites with (Star Trek) Phasers on them, and it wouldn't matter. The communications lag, seeing targets, deciding which to attack, then sharing with neighboring sats so they don't all shoot the same target is enough of an issue that many get hit multiple times, many get through since the weapon that should have killed them fired on the one already doomed, instead."

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27 minutes ago, JoeSchmuckatelli said:

There's a real difference between a stray bolt hitting an unarmored satellite and knocking out a key system, and that same bolt hitting a small, possibly armored/steel&ceramic encased warhead and disabling it.  I'm guessing that most Soviet MIRVs are relatively tough and designed back when folks overdesigned stuff to just make it work.

I wouldn't be so sure. I mean, this is what a single paint fleck did to the windscreen of the Shuttle:

Spoiler

Shuttle-window-pit-caused-by-impact-with

 

27 minutes ago, JoeSchmuckatelli said:
3 hours ago, sevenperforce said:

Would such a debris cloud actually pose a threat to ICBMs with MIRVs

That's the $64,000 question... and I'm of the opinion that 'not likely'.  Big sky, little bullet.

Yeah, I'm inclined to think similarly. Even if the debris cloud was very large, it's hard to know whether it would be dense enough to actually score a hit. Of course if the cloud was large enough then you have to think about a mean free path analysis -- it's not just about finding a single gap, but finding a path through the whole cloud.

But even if the "Kessler Dome" approach wouldn't quite work, there might be some ways to use that concept as a better way to kill MIRVs during the coast phase. Like, instead of trying to score a direct hit with an desk-sized exoatmospheric kill vehicle, your payload is designed to release a long streak of debris as close as possible to the ICBM's path, using an ascent profile essentially identical to a fast rendezvous (something we've all done in KSP when your Mun lander has way more delta-V than it needs to reach the command module and so you can just correct your bad ascent with a massive velocity-matching burn). That could have the same effect as a Spartan ABM missile but without requiring a heavy and expensive anti-missile warhead, and it could allow you to target all the MIRVs in a single launch.

What's unclear would be how to achieve that effect. The brute-force way would be to put your debris dispenser on top of something like the Spartan ABM and position your launcher near any potential targets, and just try to match the ballistic trajectory of the ICBM but in reverse. There might also be a way to do it using an orbital platform with a solid-fueled deorbit motor.

 

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8 minutes ago, tater said:

A typical US warhead is ~60cm in diameter. Assuming a lofted trajectory, its passing through the 100km orbit twice, and at a high angle, so punching through a sheet of debris. With a cross sectional area of 0.28m2, that cloud needs to be incredibly dense to ensure a hit in 1 pass, only slightly less dense to insure a hit with 2 passes.

Yeah, that seems like the biggest problem.

9 minutes ago, tater said:

Course the debris cloud idea avoids the target acquisition problem, which is a plus. A friend of mine (programmer) worked on SDI as well. He couldn't talk about his specific work, but he told me that it was all BS.

Yeah, the whole concept was about avoiding the need for target acquisition. With the real Kessler syndrome, all the objects are in orbit and so the odds of a collision go up exponentially over time, whereas you don't have that advantage here. But the idea of a long, thin band of debris tangent to the missile's trajectory seems promising.

ICBMs do tend to have a very high apogee which makes a ground-based approach seem more promising than an orbital platform approach.

Another possibility would be placing your orbital platforms in a heliosynchronous or semi-heliosynchronous orbit. This way you would need fewer platform clusters to always have Arctic Circle coverage in the same plane as any potential launch.

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42 minutes ago, sevenperforce said:

Another possibility would be placing your orbital platforms in a heliosynchronous or semi-heliosynchronous orbit. This way you would need fewer platform clusters to always have Arctic Circle coverage in the same plane as any potential launch.

Then it's a matter of what weapons the platform carries.

Directed energy is pretty much not a thing (huge energy requirements and you need to be able to engage many targets in a very short time interval). If chosen or tech changes, counters are ablative coatings on targets, decoys, spinning RVs, etc. Cheap. Also just throw more to saturate (expensive, but less expensive than sats).

KKVs (back in the day, "brilliant pebbles") have a high chance of a kill, but time of flight, and limited ammunition. Counters are decoys, and more missiles.

Even the concept you suggest has another issue—take out the sats first. Might be easier to take out the sats than the other missile-side countermeasures.

I think SDI is a good idea to have in place as a global shield against rogue states with just a handful of weapons, or as a guard against an accidental launch. Against a Great Power alpha strike... not a thing.

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The Kessler Syndrome is a danger because the odds of one piece of debris hitting anything during an orbit is low but the the risk multiplies with each orbit over time, and with each potential target in orbit. ESA estimates 330 million pieces of space junk larger than 1 mm already orbiting Earth and despite all that, there's a statistically low chance of collision at any given time.

This Kessler Dome concept requires hitting multiple specific targets in a short timeframe. For this to work statistically you might need millions of explosive single-use defensive satellites to create an effective cloud.

ICBMs can have high suborbital trajectories and spend only a fraction of a second reentering through 100 km. The odds of a piece of debris being in a warhead's path at exactly the right moment is statistically tiny, unless you have enough debris to create the equivalent of a temporary Dyson sphere around Earth. Not at all feasible with today's technology.

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40 minutes ago, tater said:

KKVs (back in the day, "brilliant pebbles") have a high chance of a kill, but time of flight, and limited ammunition. Counters are decoys, and more missiles.

It was reading about Brilliant Pebbles which got me thinking about this, actually. We have much better targeting capability now than we had in 1991, as well as much better mass-to-orbit capabilities. That increased mass-to-orbit capability could allow each "round" of "ammunition" to produce a big cloud of potential impactors rather than requiring perfect target acquisition. If you can make your transient debris field large and dense and long enough, decoys and MIRVs no longer matter because everything along the LV's trajectory is going to be shredded. But it does require that your orbital platforms either start out in the same plane as the missile (meaning you need many many such platforms) or carry enough dV for a hefty plane change.

46 minutes ago, tater said:

Even the concept you suggest has another issue—take out the sats first. Might be easier to take out the sats than the other missile-side countermeasures.

The sats would be set to activate on launch. If a Great Power state started targeting the shield sats with nuclear anti-sat missiles it would just needlessly signal their intentions and invite a strategic retaliatory strike.

 

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2 hours ago, JoeSchmuckatelli said:

There's a real difference between a stray bolt hitting an unarmored satellite and knocking out a key system, and that same bolt hitting a small, possibly armored/steel&ceramic encased warhead and disabling it. 

Update: During the Brilliant Pebbles era, Lowell Wood calculated that an impactor of 1 gram or less is sufficient to destroy unarmored objects and an impactor of ~2 kg is sufficient to destroy even the most heavily shielded warheads.

How many 2 kg plates would it take to assure a kill? That gets into mean free path analysis....

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2 hours ago, sevenperforce said:

How many 2 kg plates would it take to assure a kill? That gets into mean free path analysis....

Covering a huge % of space above the launch and target areas—and since SLBMs are a thing, that means the entire globe for the launch phase—means rather a lot of them. At 2kg, and entire Starship broken perfectly into 2kg chunks, is only 125,000 pieces. In a ~100km orbit, spread evenly, that's only 3 chunks every 1 km. The chunks sweep out ~2.6m each in the time it takes an RV to pass that plane. So the spacing needs to not be 1 per 333m, but more like 1 per 3m. So you need 100 Starships per plane, and those planes need to be ~60 apart. The Starships themselves would be an orbital hazard you'd need so many. Substantially more than it would take to "build a city on Mars."

The idea of the 2kg projectiles was that as they would each hit 1 target, you only need however many thousand of them.

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18 hours ago, tater said:

Covering a huge % of space above the launch and target areas—and since SLBMs are a thing, that means the entire globe for the launch phase—means rather a lot of them.

I think it’s obvious the dome approach won’t have sufficient coverage. I’m thinking more in terms of a Brilliant Pebbles replacement. Or in this case a Brilliant Shotgun Shell.

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2 hours ago, sevenperforce said:

I think it’s obvious the dome approach won’t have sufficient coverage. I’m thinking more in terms of a Brilliant Pebbles replacement. Or in this case a Brilliant Shotgun Shell.

Aimed, that could work. Wonder if instead of the 2kg "buckshot" something much smaller might do. Depends on the total energy of the collisions.

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7 hours ago, tater said:

Aimed, that could work. Wonder if instead of the 2kg "buckshot" something much smaller might do. Depends on the total energy of the collisions.

I have to think that smaller shots would do enough damage to cause problems on re-entry, at least.

The goal is to get your debris cloud/stream on a trajectory which not only intercepts the trajectory of the ICBM, but is actually tangent to it. That tangency means that the ICBM is traveling through your entire debris stream. This also maximizes the impact velocity, since the velocity vectors are exactly opposite at the point of tangency. If you can do this early enough, using an orbital platform with a ton of dV, then you can conceivably take out an entire group of MIRVs before they have a chance to significantly separate. If you’re using a ground-based point-defense interceptor, you’re only going to get a single warhead but it takes much less dV to pull off.

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1 hour ago, sevenperforce said:

I have to think that smaller shots would do enough damage to cause problems on re-entry, at least.

The goal is to get your debris cloud/stream on a trajectory which not only intercepts the trajectory of the ICBM, but is actually tangent to it. That tangency means that the ICBM is traveling through your entire debris stream. This also maximizes the impact velocity, since the velocity vectors are exactly opposite at the point of tangency. If you can do this early enough, using an orbital platform with a ton of dV, then you can conceivably take out an entire group of MIRVs before they have a chance to significantly separate. If you’re using a ground-based point-defense interceptor, you’re only going to get a single warhead but it takes much less dV to pull off.

I think ICBM trajectories are highly lofted.

800-1800km altitude?

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32 minutes ago, tater said:

I think ICBM trajectories are highly lofted.

800-1800km altitude?

Yes, that's my understanding as well. And that actually offers some interesting advantages, because plane changes are cheaper at higher apogees, and higher apogees have longer loiter times.

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1 minute ago, sevenperforce said:

Yes, that's my understanding as well. And that actually offers some interesting advantages, because plane changes are cheaper at higher apogees, and higher apogees have longer loiter times.

 

Even a small push might be enough to increase the CEP of the warhead. If the enemy is targeted counterforce, hard target kill requires precise targeting or huge warheads (the latter are not MIRVs). Not really helpful to the farmers who get immolated either way as the warheads aimed at the solos in their fields explode harmlessly—to the silo—several hundred meters from where they need to hit to kill it. It does provide a disincentive to first strike—which at the nitty gritty level is all that matters.

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On 3/4/2022 at 11:14 PM, sevenperforce said:

think that smaller shots would do enough damage to cause problems on re-entry, at least

One question is just how much of a knock is required to disable the warhead.  You don't need to destroy it if you can just get it to not be able to detonate.  Then it's just a falling rock with little to no boom 

 

That answer should let you know whether a bunch of smaller 'shot' would work or if you need a special warhead / missile for precision kills. 

Given the speeds - I like to think some small but dense pellets would do it 

Edited by JoeSchmuckatelli
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12 hours ago, tater said:
13 hours ago, JoeSchmuckatelli said:

Given the speeds - I like to think some small but dense pellets would do it 

Tungsten or DU, yeah.

Well I imagine that might cause problems on re-entry. A single kinetic kill vehicle is one thing, but if you are launching several thousand pellets into the path of the missile then you're talking about a LOT of bullets raining out of the sky, and tungsten won't melt on re-entry. DU will, but then you've just got a bunch of smaller DU pellets raining out of the sky. Aluminum (or iron at the most) would ensure you're not accidentally pelting an entire city with the equivalent of a few dozen A-10 strafing runs.

The real trick here is orbital mechanics -- trying to figure out how to get an intercept-at-launch tangency path for any probable trajectory using the smallest number of orbital platforms and the lowest dV per interceptor.  It's not just about entering a path-crossing trajectory, but a path-tangent trajectory, because then the missile has to fly through the entire stream of debris you've put in its path.

Obviously wouldn't work for SLBMs so you'd need point defense for that.

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1 hour ago, sevenperforce said:

Well I imagine that might cause problems on re-entry. A single kinetic kill vehicle is one thing, but if you are launching several thousand pellets into the path of the missile then you're talking about a LOT of bullets raining out of the sky, and tungsten won't melt on re-entry. DU will, but then you've just got a bunch of smaller DU pellets raining out of the sky. Aluminum (or iron at the most) would ensure you're not accidentally pelting an entire city with the equivalent of a few dozen A-10 strafing runs.

If you are using this defense system that's the least of anyone's problems. ;)

On boost phase, they rain down on people you are already raining thermonuclear weapons on, on descent, even if you manage 100% efficacy, the few casualties are orders of magnitude lower than "acceptable losses." Also, this just incentivizes cruise missiles, stand off air-dropped, etc.

Edited by tater
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