Space Force: Trump says he wants a 'space-based missile defense layer'
43 replies, posted
Yes I'm well aware of the dangers of Kessler syndrome but that was a satellite in LEO. Unless destroying a warhead can put enough force onto debris to give it enough horizontal velocity to reach an orbit, even debris from the warhead that is higher than 100 miles will only remain in a suborbital trajectory and will deorbit without posing a substantial long term risk to satellites. Other than satellites that may be in the neighborhood at the time of destruction.
I'm assuming that it can - because the amount of energy transferred in such an impact is surely enough to make smaller particles of debris enter orbit, even if it's an irregular orbit.
When in space no more thrust is provided, the missile enters free-flight. In order to cover large distances, ballistic missiles are usually launched into a high sub-orbital spaceflight; for intercontinental missiles, the highest altitude (apogee) reached during free-flight is about 2,000 kilometers (1,200 mi).[4]
Ballistic missile
Okay, so apparently they go a hell of a lot higher than I was imagining. But certainly the danger of debris would still depend on a number of factors like when it was destroyed, how far the missile was meant to go, etc. I feel like even debris from a missile on a high trajectory would not reach orbit if you blew it up soon enough. I don't know. At least we could take solace in the fact that such a weapon would hopefully never need to be used.
The idea of a Space Force is pretty out there, but I think its a very plausible. China is beefing up its military, but primarily in the cybersecurity sector and space program.
No, it's extremely likely to be used if this degenerate puts missiles in space. It doesn't matter whether they're used on nuclear missiles or owner defensive satellites, such a move would virtually guarantee Kessler syndrome in the long term.
Is it possible that Russia wants this? I feel starting global tensions that help Russia assert their dominance over the rest of the world is a big part of why they backed Trump. Plus making an enemy of the other is a great way to control a populace.
we already have a space force inside the airforce.
further, their goal is no different than Trump's spaceforce because we're not going to be sending men up there to guard satellites.
the three goals of any space defense force are
1) tracking of all objects and cataloguing, standard stationkeeping to maintain the infrastructure there and deploy replacements as needed
2) develop countermeasures to anti satellite weaponry, this involves many things from blinding of optics to having replacement satellites ready in case of an attack on space based infrastructure, to cyber defenses.
3) develop our own Anti Sat strategy and capabilities
trump's spaceforce has some nebulous handwavey plan to put people up in space and fight wars there but besides that we're already doing enough.
in fairness Trump thinks McDonalds is great so he doesn't consider it an issue
I had kind of wondered if Russia would want this because it breaks treaties that then allows them to break treaties in return. I don't know, in this age of conspiracy theories made real, it's hard to figure out what would be too crazy to be true.
I did some calculations to hopefully clarify how easy it is to shoot debris into orbit from a icbm interception, both to satisfy my own curiosity and contribute to the discussion. My method was determining the energy required to put debris into orbit, and whether a interception could provide enough energy to put it into permanent orbit. I took the approach based on energy since there are a lot of unknowns, such as the shape and nature of the debris after interception.
Starting with the average trajectory apogee height of 2000 km given by the wikipedia article you linked, I needed more information to compute the horizontal velocity at that point. According to the National academic press a average ICBM has a burnout velocity up to 7.4 km/s. For the sake of simplicity I'm going to assume a ballistic launch and neglect air resistance since it is a Sunday morning and this is a rough first order approximation. Using the Vis-Viva equation of orbital energy retention I can work out that at a apogee of 2000 km altitude the ICBM will have a horizontal/tangential velocity of 4986.387 meters per second. At this altitude the orbital speed for any small (negligible weight compared to earth) is 6900.5 m/s, computed using the orbital velocity formula.
Thus to bring a piece of debris into a circular orbit at this apogee, there needs to be a velocity change of 1914.1 meters per second in the tangential direction. This might sound like a lot until you look at just the energy involved. The specific kinetic energy to make this happen is only 1.8319 MegaJoule per kilogramme of mass, computed using the kinetic energy formula. Again, this might seem a very big number but if we consider a paint flake of roughly 0.5 grammes this boils down to only needing 915.96 Joules of energy to be accelerated enough to orbit Earth permanently. Obviously, more energy is needed the larger and heavier the debris but these very small parts are the most problematic since they can't be tracked.
Finally the method of interception needs to be evaluated to determine the true danger. The most reliable way to intercept a missile travelling at 4986 meters per second from space would be a short range interceptor missile launched from a nearby satellite. The design and specifications of these are not as easily found, but for comparison sake let us assume that one of the slowest and least energetic missiles was sufficient. So lets assume a satellite could fire a RPG-7 accurately enough to intercept a ICBM at its apogee, the RPG-7 VL warhead weighs approximately 2.6 kilogrammes and has a flight velocity of 300 meters per second. This means that the missile has a kinetic energy of 117.0 KiloJoules at its flight velocity.
Just the kinetic impact alone, from a RPG-7 VL warhead could thus in the worst case produce 127 0.5 gram paint flakes and put them into circular orbit around Earth. This is not the most realistic scenario for a interception, it is not likely that it will completely transfer its energy to 127 small paint flakes, but I hope to show that the energy is there to produce serious debris hazards. For these calculations I also haven't accounted for the energy provided by the explosive filler of the warhead, so assume the problem would be much worse.
Now realistically for a ICBM interception you wouldn't use a RPG-7 rocket but a interceptor missile which would be much,much faster as it needs to be able to catch up with the ICBM travelling at 4986 m/s. Thus they have to travel at least 16.62 times as fast as the RPG-7 rocket, and since kinetic energy scales with the second power of velocity their specific kinetic energy is at least 276.2 times higher than the example I used. These missiles will have to be much heavier and likely pack a larger warhead in order to reliably intercept a ICBM as well. What I'm trying to show is that a RPG-7 rocket already has the potential to be very problematic in terms of space debris, and a real interception missile will just make the problem much, much, much larger.
As a final note, if you were to try to intercept a ICBM from space the apogee would also be the best point to do so, since at this point the ICBM's velocity is lowest. Dealing with space debris, the problem would be of much smaller scale if the ICBM would be intercepted earlier or later in its orbit, preferably in its atmosphere. But in these phases it is much harder since the velocity is way higher. Thus if a space-missile defence system is to be implemented, it is a very valid assumption that the ICBM is intercepted in its apogee.
TL;DR: Some quick calculations show that intercepting a ICBM at its apogee of 2000 km altitude with a handheld RPG-7 already has the potential to launch space debris into orbit, even when warhead explosive energy is neglected. Real interceptor missiles contain at least 267 times more kinetic energy (travel at least 16.6 times faster), are much heavier and have a much bigger warhead, so there is a very direct threat of introducing a lot of space debris with a single interception. Also the apogee is the easiest point to intercept a ICBM within its trajectory, so it is reasonable to assume this is where the military would do it.
Can't see them getting enough space based countermeasures to matter in a nuclear exchange with say Russia, but wouldn't it be conceivable that in a few years the US could render a North Korean strike on mainland US minimally threatening?
Imagine if all of this is what gets us back into a space race, of all things
We would need something like a geo-synchronous net to catch that debris, but also a net that can decide what gets and and out. We don't want our orbiting objects to get caught.
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