(ORDO NEWS) — The creation of a grand constellation of Starlink satellites will demonstrate fundamentally new qualities that are beginning to appear in extremely large satellite systems. Their ballistic capabilities may turn out to be unexpected and will allow the use of such a mega-group at all for other than its main purpose.
For example, you can quickly turn some of the peaceful satellites into weapons and complete a combat mission, and then return the satellites to their normal work. Naked Science wondered if that was possible.
SpaceX continues to expand the orbital constellation of Starlink communications satellites. Its final composition should reach an unprecedented number of satellites in history.
What it will actually be, we still do not know for sure, but we can expect that the total number of satellites in the system will reach several tens of thousands of units. This is enough for her to become a new type of weapon.
Orbital constellation Starlink: the structure of a growing giant.
A single satellite is a flat panel weighing 260 kilograms. The panel is about 3 m long, 1.5 m wide, and 0.2 m thick. The satellites are equipped with one solar panel and an electrostatic Hall motor with krypton as the working fluid. To perform their main task, satellites are equipped with various types of antennas.
SpaceX is currently building its first-generation satellite network, which consists of two parts. The first part will consist of 4408 satellites placed in layers at altitudes of 540, 550, 560 and 570 km. Each layer contains 4 to 72 orbital planes and 520 to 1584 satellites.
It is in this first part that Starlinks are now being launched. During 2021, 19 launches were made, the number of working satellites in orbit reached 1944. And in January 2022, the number of working Starlinks exceeded 2000.
The second part of the first generation satellite network will contain 7518 satellites in three layers at altitudes of 336, 341 and 346 km. Together with the first part being completed today, the first generation satellite network should have 11,926 satellites.
The network of new generation satellites will be much more numerous. In October 2019, SpaceX submitted an application to the Federal Communications Commission (FCC) to launch 30,000 second-generation Starlink satellites into operational orbits between 328 km and 614 km.
In August 2020, the company asked for changes to its application related to the possibility of launching satellites in large groups on the Starship carrier. However, the total number of satellites and the altitude range remained unchanged.
Plans for the final configuration of the Starlink group change over time. According to SpaceX’s most recent letter to the Federal Communications Commission (FCC) in January 2022, the completed second generation Starlink constellation will consist of 9 orbital layers located at altitudes 340, 346, 350, 360, 525, 530, 535 , 604, 614 km.
The layers will contain from 12 to 48 orbital planes, in each of which 110 – 120 satellites will move (in the two upper layers, 12 and 18 satellites in each plane). The total number of satellites will be 29988 .
Before that, we had heard about plans to increase the constellation to 42,000 satellites. So far, they have not been reflected in applications to regulatory federal agencies, but with the commissioning of the super-heavy Starship, capable of launching about 500 satellites in one flight, we can expect such applications to arrive and a sharp acceleration in the build-up of the Starlink constellation.
Orbital collision threats.
Such a multitude of satellites, concentrated in the low-orbit altitude range, creates an unprecedented high density of devices in space. And this gives rise to a high risk of collisions with other spacecraft (which causes concern for their owners) and the need for maneuvering in order to avoid orbital accidents.
Already, every week there are about 600-700 dangerous encounters of Starlinks at a distance of a kilometer or less with other spacecraft. With an increase in the number of satellites up to 30 thousand, the frequency of such situations will increase by a couple of orders of magnitude.
Currently, Starlink satellites use autonomous maneuvering to avoid collisions with other spacecraft or objects tracked by NORAD (North American Aerospace Defense Command, North American Aerospace Defense Command). NORAD data is fed to the Starlinks, and if necessary, the satellites autonomously make a decision, calculate the evasion parameters, and produce it.
But a huge group of 30,000 will require an additional control channel in the form of a unified system for managing the movement and the general state of the group. The autonomous actions of each satellite alone will not be enough to control the entire system in a stable manner.
A complete model of its movement will be needed, constantly updated on the actual measured parameters of satellite movement. One of the tasks of this model will be the redundant control of spacecraft collision avoidance. And here, for sure, there will be a need to adjust the movement of not only single vehicles, but immediately large groups of Starlinks.
This duplication of control over the safe movement of the Starlinks will be required because all spacecraft that will subsequently operate above pass through the low-orbit range occupied by the Starlinks during the launch process. It also houses other low-orbit space systems and vehicles, including manned ones.
And this is not only the ISS, but also Soyuz, Crew Dragon, and soon other ships will appear there, both with missions to the ISS and with independent flights. Collision safety will be one of the key parameters for the Starlink constellation’s overall traffic control system, along with planetary broadband coverage and optimization of satellite power consumption (the consumption of xenon reserves for the engine).
And, it would seem, everything with the Starlink grouping is obvious: the goals of controlling its movement (providing the calculated coverage of the Earth with a satellite constellation and avoiding collisions) and common goals (providing broadband Internet access to the inhabitants of the Earth) are clear.
Another look at the large orbital system.
However, you can also look at the very ballistic essence of the Starlink network in a different way. A very large satellite constellation represents multiple high-speed bodies loitering in space. Precisely due to the fact that there are a lot of them, and they are “present everywhere,” they can be considered as a kinetic means of destruction, which is in preliminary readiness and in sufficient quantity over any area of the globe.
Let’s reformulate the definition of “frequent threat of collisions” and get another one: “a large satellite network keeps other satellites at gunpoint that it can destroy”
We noted above that Starlinks often pass just a kilometer from other satellites – this medal has a downside. It is that it takes very little momentum to reduce this distance to zero. Which can be set, due to its smallness, even with a weak engine, and quite quickly.
Roskosmos and NORAD are still silent about this nuance. Roskosmos, perhaps because it is not ready to recognize the growing threat to the Starlinks orbital network, and the NORAD ballistic object tracking system does not deal with combat strategies at all, its job is to track objects and their current movement, and calculate trajectories and forecasts.
Probably, before the real prospect of building extremely large satellite systems, such approaches simply did not arise; it never occurred to anyone to perceive a large orbital constellation from this angle (or it did, but we don’t know about it yet).
Target interception by one satellite of another, or orbital interception, has been worked out for a very long time. In orbital ballistics, there is such a wide area as the dynamics of rendezvous of spacecraft. It describes the mutual, that is, relative to each other, the movement of vehicles in orbital flight.
At the same time, the devices themselves are relatively close to each other, in the range from hundreds of kilometers to tens of meters. Their proximity simplifies the systems of differential equations describing their mutual motion to difference equations of motion.
For example, docking in orbit is a classic problem from rendezvous dynamics. The solution to the ballistic problem of docking will be the practical coincidence of the orbits, especially in the spatial region and at the moment of docking. As well as limiting the rendezvous speed at the moment of docking to a technologically acceptable one, that is, very small.
But you can cancel the speed limit – and even, on the contrary, set the relative speed high enough. For example, not lower than 100 meters per second (this is 360 km / h). In the event of a collision with the hulls at such a speed, both devices are guaranteed to stop functioning. And here is the situation of interception by one satellite of another, in which two peaceful satellites turn into an interceptor and a target.
With a high relative speed, the orbits of the vehicles cannot be the same. But the restriction on a high degree of coincidence of the orbits of the target and the interceptor is removed. It is only important that their orbits intersect, and both devices are at the intersection point at the same time.
Typical orbital chase scenario.
An orbital interceptor’s pursuit of a target requires a series of successive interceptor maneuvers. Let’s consider the simplest example. The target and the interceptor are in the same circular orbit, at a distance of one hundred kilometers from each other. How can the interceptor catch up with the target?
If he simply turns on his engine for acceleration, he will not catch up with the target, because the orbit is not a road: an increase in its speed will raise the opposite part of the orbit, forming an apogee there. The interceptor will rush to it along a new orbit, which will diverge from the original target orbit, excluding hitting it.
The interception will have to be built differently, according to the rules of orbital ballistics, that is, in a somewhat paradoxical way for our everyday ground perception. To catch up with the target, the interceptor makes not an accelerating, but a decelerating impulse with an engine.
This lowers its orbit, creating a perigee over the other side of the Earth, to which the interceptor rushes, starting its descent. Having lowered its altitude enough, the interceptor makes a second impulse, now accelerating – this will stop further descent, leaving the interceptor in a lower circular orbit.
The lower the orbit, the faster the speed of circulation along it, both linear and angular. It’s like the clock face is reversed – the short hour hand of the orbital movement runs faster than the long minute hand. At the end of the fast hour hand, at a lower altitude, is the interceptor, at the end of the long and slow minute hand is the target. In such a situation, the interceptor will overtake the target in its lower orbit.
And when the distance to the target is small, the interceptor will make a third pulse, also accelerating. After it, the height of the interceptor’s orbit will increase with the intersection of the target’s orbit. It remains to coordinate the maneuvers of the interceptor with the movement of the target in such a way that both vehicles are at the point of intersection of the orbits simultaneously. And met.
Similarly, with the construction of a scheme of several maneuvers, it will be necessary to organize an orbital interception in real and more complex cases. With different initial orbits of the target and the interceptor – with different inclination of the planes of the orbits, different heights, different “elongation” or eccentricity, different orientation of the axes of the orbits and lines of nodes in space. A sequence of interceptor orbital maneuvers will result in a high, combat level, target interception probability at a given design point and time.
Due to the need for a cascade of maneuvers, orbital interception was not developed and the creation of operational combat systems. And not only because the deployment of weapons in outer space is prohibited by international treaties. It is quite difficult and cumbersome to launch an interceptor satellite into orbit by a launch vehicle, and then perform changes in its orbit until the orbital target is intercepted.
The development of anti-aircraft missiles and high-altitude interception led to the creation of anti-satellite missile systems. Their warhead is not an orbiter, is not in orbital motion, and does not require successive orbital maneuvers to intercept a target.
Orbital interception of a fundamentally different type.
However, orbital interception may turn out to be a broader concept: it is enough to go beyond the traditional format in which a solo interception of a target is performed by a single interceptor satellite specially chasing a target.
Interception can be fundamentally different. You can not set the task of guaranteed interception of the target by one specific interceptor device. A large satellite network creates other possibilities. You just need to set the opposite task to the control system for the movement of the orbital constellation.
Such, for example: not to avoid collisions with other satellites, but on the contrary, to maximize the probability of a collision with target satellites. Under the goal we mean a specific spacecraft, the orbit and motion parameters of which are known, and whose flight must be stopped.
It is possible to purposefully create a dangerous approach with a satellite from the orbital group on the target trajectory – with a relatively small, but still significant collision probability
A single dangerous proximity situation will not lead to a guaranteed interception of the target. But dangerous encounters can be created on the target trajectory in a multitude, like beads on a string – sequentially, one by one, ten by ten.
And the target will “permeate” these dangerous encounters in the same successive manner, as they arise (create on its trajectory), in each experiencing the probability of a collision. If there are many such approaches, then the total probability of a target collision, as a result of the passage of the target through all the approaches, will increase.
By increasing the situations of possible collision, it is possible to bring the total probability of intercepting a given target to combat values. For example, up to a probability of 0.8, or 0.9, or 0.99. The decision will be based on the probabilities of collision in encounters (they may be different), and the number of such encounters. With a sufficiently large number of approaches, the interception of the target will reach the required reliability.
The resulting overall probability of such an interception is not concentrated at one point in the target’s trajectory, or at one selected point in time, as with a conventional “solo” interception. It will be “smeared” along the target’s trajectory, along many dangerous approaches on it, and many points in time. Therefore, it is impossible to say in advance in what approach and when the collision probability is realized in the actual event.
As the number of dangerous encounters increases to a sufficiently large number, the increasing probability of a collision will lead to a real interception event. You can call this method distributed group orbital interception
The krypton engines of Starlinks have low thrust, but it is quite enough for evasive maneuvers. Let us recall once again that already today there are multiple situations of satellite divergence at a distance of one kilometer or less. It is necessary to determine with which Starlink satellites the target has similar predicted encounters.
The orbital constellation traffic control system identifies Starlink satellites that can create a dangerous approach to a given target in the next day or at another time interval, subject to a slight adjustment of their orbits. There may be quite a lot of such satellites among a group of many thousands, perhaps many tens or hundreds.
At the command of the constellation motion control system, the selected satellites change the evasion task to the rendezvous task. They start the orbital maneuvering engines, and begin to change their orbital motion so that the number of dangerous approaches to a given target begins to increase.
Starlinks can calculate the task of the meeting autonomously, or the operation of their engine will be commanded by a common network management system. This is how group orbital interception of a target begins . After some time – for example, a day – the risk of collision of the involved satellites with a given target reaches combat values. In the course of which the collision itself is realized. Target interception completed – distributed group orbital interception.
Features of new approaches
We can say that using so many Starlink satellites for the sake of one interception is irrational. But only one satellite will be used up. The rest can safely return to their original orbits, or to a new configuration that ensures the implementation of basic communication tasks. Yes, the group of satellites involved in the interception will have an unplanned consumption of krypton, this will reduce its reserves and shorten the service life of these satellites.
But how much will it reduce? Perhaps not so significant. After all, the control system will select those satellites that require minimal corrections. This additional expense will not take the satellites of the intercepting group out of service immediately. And SpaceX plans to launch Starlinks with a large Starship, which will launch about 500 satellites into orbit at once (for different orbits, the number of launches will vary) in one launch.
This can easily compensate for the decrease in the service life of satellites from the interception group. With a large-scale satellite constellation (do not forget – 30 thousand satellites!) the intercept over expenditure of krypton for hundreds of satellites will not only not be critical, but also invisible to the entire system.
Group orbital interception will be much more effective when working not on a single target, but on several at once
Group orbital interception will be much more effective if you need to intercept not a single target, but several targets – ten, thirty or fifty. For example, when tasked with destroying a space constellation: communications satellites, or reconnaissance satellites.
Then the satellites from the interception group can pose a threat not to one, but to several or many targets at once. This will significantly increase the effectiveness of interceptors, and the effectiveness of group interception. A gradation of interceptors according to the number of targets is possible. Some of the interceptors can create a dangerous approach for only one target, others – for two targets, three targets, N targets.
It will be necessary to develop complex models of the movement of the satellite system that can best organize the construction of orbital interception groups. With the optimal number of interceptors in the general group, with the distribution of targets between the interceptors, with the sequence of changing the orbits of one or another category of interceptors, with minimizing the consumption of krypton. When developing schemes and methods for orbital group interception, effective algorithms for predicting and performing a combat mission can be built.
Who to aim at: a wide range of targets.
What combat goals can the Starlink orbital group have? This question can be answered by evaluating the possibility of changing the orbits of satellites that become interceptors. The further up and down from the base height the interceptors must move, the longer the interception will take and the more unplanned krypton consumption.
Therefore, the high-altitude range of interception is expected to be small, within 50-100 kilometers up and down from the height of the base orbit. However, this range covers several types of possible targets quite well, because it extends from low reference orbits to altitudes in the region of 700 km.
First, optical reconnaissance satellites in sun-synchronous orbits fall into it. The operating altitudes of such orbits are just in the range of 550 – 700 km. And the population of orbits of this type will grow due to the great advantages of sun-synchronous orbits for observing the earth’s surface in the optical range.
Always the same local time at each sub-satellite point, and accordingly an unchanged shadow pattern from objects on the surface, makes it easy to detect changes in the terrain. In other applications of solar-synchronous orbits, they provide continuous round-the-clock illumination of the vehicle and its solar batteries, which is very suitable for continuous radar work from orbit.
Secondly, the targets of Starlinks can be low-orbit satellite communication systems. The third type of targets can be satellites in elliptical orbits with low perigees, located in height within the reach of group interception. In general, any satellites operating at the heights of the designated range, or passing through it during the stages of their flight, can serve as targets.
It could be argued that Starlinks, with their weak thrust, would take too long to create a combat probability of interception. But the combat mission of interception usually requires the destruction of the target in a given time, and “not someday, as lucky.”
But if the satellite has time to evade another satellite in some operational time, it can also have time to move towards it (and have time to get close to it). In some cases, he may be late with the creation of a dangerous approach, and in other cases (or another satellite) it will succeed. And just such “successful” satellites are activated by the control system.
On the one hand, it is difficult to predict all the variety of possible tasks for group orbital interception. The limits of its capabilities are now not entirely clear, as well as the specifics of its organization. And it is quite possible that the development of methods and algorithms will reveal situations where the use of orbital group interception will be justified and make sense. An analysis of the military effectiveness of group orbital interception is beyond the scope of this article; we consider the ballistic interception capability itself.
On the other hand, the development of algorithms for orbital group interception and the determination of areas of its effectiveness can lead to a targeted possibility of its application. Then it is also possible to strengthen future generations of satellites from the point of view of the group interception potential.
It is possible to equip future satellites with a solid propellant engine weighing 3–5 kg, by analogy with the solid propellant apogee engines used. Such an addition to the design will not significantly affect the cost or mass-dimensional characteristics of the device. But it will allow changing orbits for interception more quickly, increasing the combat potential of the satellite constellation.
From Key Elements to Strategy and Tactics.
Distributed multicast orbital interception requires three key elements. First, a fairly large constellation of satellites, preferably distributed over a range of altitudes. Secondly, large computing power and an adequate detailed general model of the movement of the orbital constellation and probable targets. And finally, the ability of the satellite to perform the necessary orbital maneuver.
For group interception, only three key conditions are needed – and the Starlink system can fulfill them.
When these conditions are met, the construction of a distributed orbital interception system becomes possible. And with the strengthening of each element, the interception efficiency will increase. With purposeful development in this direction – to practical combat effectiveness.
There may be strategic considerations when building other satellite systems. If they are created in the same altitude range or close to it, it will be necessary to take into account the threat of global interception of this satellite system by the 30,000 Starlink orbital constellation.
There may also be tactical advantages to such an interception. Its start is imperceptible, in contrast to the launch of a rocket from the ground with its bright infrared exhaust plume. The launch of the Starlink engines used as interceptors will occur in many places in the satellite constellation, evenly distributed over it, not standing out among other engine firings for the current orbit correction.
And in itself, such operation is not too noticeable due to the peculiarities of the electric propulsion engine. What the change in the orbits of satellites that have become interceptors will lead to will not be immediately obvious to the NORAD system or other systems for controlling the movement of ballistic objects.
True, so far there have been no official plans to use the Starlink orbital constellation as an orbital interception system. But this does not mean that the very principle of distributed orbital interception does not exist. With an increase in the number of satellites, the ballistic possibility of such an interception increases. Sooner or later it will be realized and properly appreciated.
Instead of an epilogue.
The philosophical law of the transition of quantity into quality also works in outer space. The previously unimaginable number of satellites in a single orbital constellation under common control creates opportunities that were previously difficult to predict. However, it would be far-sighted to take a closer look at these opportunities today, when an extremely large satellite constellation is already being created.
The immediate prospect of the full deployment of the orbital megagroup is quite real. If successful, new ballistic capabilities will also arise. And fundamentally new approaches to traffic control, allowing at any time to select the required combat segment from a general-purpose satellite network that does not have any weapons on board.
The assessment of new applied aspects of ballistics of large groupings is overdue, and this article can be considered one of the simplified versions of such an assessment. How the extremely large orbital constellation and its additional capabilities will develop will be shown in the coming years.
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