If you're talking about intentional physical interference, aka anti-satellite weapons, the solution to that is having the ability to rapidly replenish the constellation (SpaceX is good at this, and with Starship they'll be even better at it; hundreds of replacement satellites with a single launch.) In the event of a war, a constellation could be kept operational through the brute force of launching more satellites faster than they're destroyed. Of course this will make a huge mess, but that's what wars do.
Anyway, they're going forward with this already. The National Defense Space Architecture calls for a very large constellation of LEO communication satellites forming a mesh network using inter-satellite laser links. Starlink is likely dual-use technology and has been intended as such from the start.
I mean, LEO is still harder to reach out to than almost anywhere on Earth.
The main deterrent to attacking our assets in LEO or on Earth is that such an act would at least have some serious political fallout, and potentially start a war depending on how annoying it is.
Big picture, even if Russia and/or China managed to turn LEO into an impenetrable barrier of debris before the war was lost for them anyway, what would they actually have accomplished? The satellites that previously acted as America's shield would now be debris that would continue to shield America, and America would still have Aegis BMD around the world. Symmetrical war with America is beyond stupid, there is no balance, no fair fight. The purpose of these systems is to ensure that it stays this way, so that nobody tries in the first place.
As for why, maybe the reason wouldn't even involve America that much. Maybe China decides to take Taiwan, and to prevent America from interfering, they choose to destroy LEO for everyone. Maybe it would be an acceptable sacrifice for them, as they are more interested in controlling their neighborhood than projecting power to faraway places.
Not very big actually, not if the interceptors are placed in LEO. They're a hell of a lot smaller and cheaper than the missiles they're meant to intercept. The kill vehicles themselves are only a few kilograms, very small and light weight. For such light-weight interceptors positioned in LEO, you don't need much booster to get the job done. You can get away with a booster much smaller than an SM-3.
> Because they have only a few minutes to hit before the target deploys the payload, they would have to expend lots of delta-v to guarantee intercept
The more you have, the less delta-v they need. That's why Brilliant Pebbles proposed thousands if not tens of thousands of them. Launching such a huge number of interceptors would be possible with Falcon 9, but Starship would be much better at it.
> Maybe China decides to take Taiwan
Maybe they would, but they would have to be insane to start a symmetric war with America itself. And that's the whole point.
> Deploying such large-scale missile defense systems would be obvious to everyone.
If you've been paying attention, you'll have noticed that China and Russia haven't been very secret about their interest in countering Starlink. It's not because they're afraid the US might give uncensorable internet to Chinese and Russian people, as I've seen some on HN speculate. They obviously perceive the strategic threat already. Besides starting the war first, there's not a whole lot they can do about it. If they start the war first, start it now, they'll probably kill a lot more Americans than if they wait and do it later. But that doesn't matter because they'd still all die, so they aren't going to do it. Neither China nor Russia has a BMD system that could prevent America from killing them all.
[0]"While boost-phase defense has been advocated as the most efficient way to deal with fractionated payloads and exoatmospheric (midcourse) penetration aids, it is extremely sensitive to assumptions about threat booster characteristics. Over time, boost-phase defense tends to be renamed ascent-phase defense when the kinematic realities set in. In fact, ascent-phase defense is code for engagement in the postboost or early midcourse phases of flight.
The limitations and complications of a surface-based boost-phase defense lie primarily in the concepts of operations (CONOPS), policy, time, and geography. Since the timelines for engagement in the boost-phase are extremely short, the on-site commander must have authorization from the National Command Authority to launch an interceptor immediately after a threat missile has been detected.1 Also, access must be gained to countries adjacent to the threat country in order to position a boost-phase system close enough, and at the correct geometries, to successfully engage the threat missile. Finally, boost-phase systems are only effective against countries that do not have large enough landmasses to allow them to launch missiles from deep within their territory.
The airborne laser is designed to deliver energy at the speed of light to perform the boost-phase intercept mission. Space-based lasers were also pursued in the past. Virtually no fly-out time is involved, and the beam agility is a function only of how fast the pointing optics can be repositioned. While laser weapons sound like the obvious answer, the energy that a laser can deliver on a target is limited by the power available and the aperture of the device. Atmospheric effects disturb the beam. Much has been accomplished in advancing the pointing and tracking capabilities and the adaptive optics to maintain beam quality, but some fundamental limitations remain."
"Fülöp and colleagues argue that the energy problem could be overcome by splitting the laser pulse into two equal-energy pulses, which then hit the target simultaneously at different, precisely calculated angles of incidence (see figure). Through simulations, the team showed that when the laser pulses collide, a standing wave forms inside the solid target that increases the peak electric field. With the same pulse intensity used in previous experiments, their calculations suggest that the technique can double the energy of the proton beam and produce five times as many protons — all with far more flexible control parameters than required before.").
[0] https://physicsworld.com/a/laser-collisions-could-boost-prot...
Look up SDA and the National Defense Space Architecture. They're talking about thousands of satellites in LEO. They call it pLEO (proliferated LEO.)
As for Brilliant Pebbles, that's one reason it's a total failure, but not the only one.
I'm sure targeted options will be favoured by most parties.
Yah. Slightly favors your own satellites in the odds, but not wonderfully so.
At the same time, if you're facing an adversary which depends upon LEO much, much more... this might be an attractive strategy.
Fighter jets use missiles, not flak. Above certain velocities and a certain degree of freedom in the third dimension, shotguns disperse uselessly more than hit anything. At the point you're getting close enough to make a hit probable you're already most of the way towards a direct strike anyway.
Do you think the missiles go and touch the opposing fighter jet? Hit-to-kill systems exist, but most missiles maneuver, get as much of an intersecting path as they can, and then explode to kill the target with fragments.
> At the point you're getting close enough to make a hit probable you're already most of the way towards a direct strike anyway.
Here, you don't select for the highest probability of kill on a certain pass, but instead the highest probability of damage integrated over many orbits. You also don't select for the highest probability of killing a given SV, but of killing satellites in a given constellation with closely related orbits.
Which is the "getting close enough to make a hit probable" I described.
> don't select for the highest probability of killing a given SV, but of killing satellites in a given constellation with closely related orbits
I get the hypothesis. But if you run the orbital math, interaction is vanishingly unlikely. Kessler syndrome is triggered by massive orbital objects breaking up and creating a domino effect at high altitudes, where orbital decay is minimal on human timeframes. Kessler concerns were raised with respect to Starlink, but I haven't seen anyone balance the math for massive numbers of small objects. Even for the classic case, when you actually run simulations, most objects don't interact.
E.g. a Falcon 9 can put 14 tonnes into a higher LEO. Assume you fill it 90% with 1cm diameter tungsten spheres, and the rest with an optimized dispersal system. That's 1.26 million spheres slowly decaying through your target orbit, and you can end up with a favorable initial phase, altitude, and inclination.
You'd be tripling the amount of debris of that scale in orbit in one launch, in a way that's disproportionately targeted at a specific constellation.
(Probably 1cm diam is still excessively large. Also, when we talk about the original idea, you could have many smaller, even more optimized shots at individual spacecraft in the constellation).
Three degrees of freedom are deceiving. Millions of projectiles sounds like a lot. It’s not.
You could do this hundreds of thousands of times in LEO and thousands in MEO and still barely change a single satellite’s collision odds.
> You could do this hundreds of thousands of times in LEO and thousands in MEO and still barely change a single satellite’s collision odds.
I have to think that multiplying the number of debris objects by 300,000 for a few months *, and preferentially targeting that debris at a specific satellite would change its odds a bit. So, you're way off in hyperbole-land at this point.
Of course, it all depends on what we mean by "targeting". Still, one launch gets you approximately 3x the total amount of debris in orbit, and the opportunity to choose how it's distributed.
* Objects with a mass/surface area ratio of ~15 kg/m^2 decay in about a year in LEO, depending upon space weather and other factors. The tungsten balls have a ratio of 32 kg/m^2, so can be expected to last a fair bit longer.
If a million projectiles in one orbit isnt something to worry about then why are we worried about Kessler Syndrome with the thousands of satellites and junk that is already up there?
One, Kessler syndrome should really be called the Kessler hypothesis since we’ve never actually proven it’s a problem in any real form. To the degree it’s been rigorously modelled, it would create a lot of property destruction in a limited number of orbital planes, not block access to space. The problem is breaking stuff. Not blocking. Two, where it’s been rigorously modelled and shown to be a problem (again, only for a limited set of planes) it derives from something big breaking apart. Not lots of small stuff. And again, we’re talking about a bunch of property destruction. Not annihilation of everything in the plane let alone orbit.
Second, take the volume of the entire shell around earth from 400km to 450km up-- that's about 3 * 10^19 cubic meters. 1.3 million objects scattered randomly over this entire volume yields a density of 4 * 10^-14 / m^3, which sounds like a small amount, until you consider that a moderate sized object orbiting at that altitude might sweep 20000 m^3/second. You'd expect this indiscriminate attack on LEO from a single launch to hit 2.5% of objects with this 2.5 m^2 cross-section in the year that the BBs stayed in orbit. You'd expect to hit the ISS about once every 2 hours and to accrue hundreds or thousands of hits.
To the extent that you focused your attack on certain planes and on a narrower range of altitudes, you could expect it to be more effective. And, of course, to the extent that there's any further fragments created / Kessler-type effects, you can expect more effect.
Starlink 2 appears to be more than a metric ton, but none have been launched.
This has been pretty hush hush, but voters should know what they're getting in the midterms if they support this. In my opinion it will indeed lead to WWIII. I think Elon knows that but justifies it by thinking he needs the military industrial complex funding for Mars.
[1] https://www.hudson.org/research/17482-nuclear-weapons-china-...
[2] https://en.wikipedia.org/wiki/Starlink#Military_satellites