SURTUR
OCT 14, 2026
In the last article I talked about how reusable rocket technology could enable armed forces to cheaply launch thousands of conventional payloads at intercontinental ranges.
Here I'll explain how these warheads could hit both fixed and mobile targets with the support of next-gen satellite constellations.
Weapon guidance sensors and reentry
Weapons can use a variety of sensors to determine their relative position to the target and accurately steer towards it. The harsh conditions encountered by long-range ballistic weapons when they reenter in the atmosphere however complicate the use of many sensors like optical and radar, driving up costs and complexity.
For example, long-range Anti-Ship Ballistic Missiles (AShBMs) like the Chinese DF-26 need to slow down to speeds below Mach 5 before they can use their onboard radar seekers. In fact, at higher speeds, a plasma sheath surrounds any object moving through the atmosphere, interfering with the transmission and reception of the radio waves used by radars.
Since an AShBM warhead can only see its target after it has slowed down significantly and has only about 15-20 seconds left to correct its trajectory, it may miss the target entirely even if it's designed (at high expense) to be highly maneuverable.
In general guidance systems reliant on external sensors are a bad fit for relatively inexpensive warheads to be produced in the thousands: small and light sensors robust enough to survive reentry aren't cheap.
Inertial navigation
This is also one of the reasons why the most common guidance system used on ballistic missiles relies instead on an Inertial Navigational System (INS) paired with a Global Navigation Satellite System (GNSS). Let's explain these terms.
An inertial navigational system is a device that can accurately measure its acceleration, using this data to then calculate an estimate for its speed and position. Since successive integration steps are used even small accelerometer errors compound with time resulting in warheads missing the targets by up to a couple of kilometers.
Current navigational satellite constellations
A way to accurately determine the position of a warhead in flight is therefore needed to periodically reset the errors accumulated by the INS.
This can be achieved through the reception and processing of multiple radio signals each encoding a precise timestamp and data on the position of the transmitter: this is working principle behind GNSS constellations like GPS.
Current GNSS satellite constellations however have a number of weaknesses: since they use expensive atomic clocks each constellation only has a few dozen satellites, this not only makes them a very attractive target for anti-satellite weapons but forces them to use Medium Earth Orbit (MEO) to provide adequate worldwide coverage.
Since the MEO orbits used by GNSS satellites are 20000 km from the Earth and each satellite must broadcast signals to a large surface, GNSS signals are very weak and susceptible to jamming, a vulnerability exacerbated by the fact that these satellites use signals with frequencies in the L band, a very crowded section of the electromagnetic spectrum, and so only have around limited frequency bands available for their transmissions (the electromagnetic spectrum is split in a number of frequency bands each reserved for a specific use to avoid mutual interference). This means that a jammer can focus a lot of power in a limited section of the spectrum, drowning the weak GNSS signals in noise.
A way to reduce the impact of jammers is using composite antennas called CRPA (Controlled Reception Pattern Antenna). These antennas are capable of reducing the reception of signals coming from certain directions by processing the signals received by multiple smaller antennas, however if there are jammers transmitting from many different directions the CRPA needs to be larger: in Ukraine some Russian drones fly with CRPAs of more than 30 elements to have a chance to intermittently receive GNSS signals.
However these large CRPA antennas can get pretty big and are unsuitable for warheads with limited available space: elements of a GPS CRPA needs to be spaced by about 10cm, the length of the half wavelength of the radio signals they are designed to receive.
Future navigational satellite constellations
These issues can be solved by building a GNSS constellation using thousands of modified starlink V3 satellites.
This is quite practical since Starlink satellites are being cheaply mass-produced by SpaceX, and are already equipped with laser links that could be used to accurately measure the relative distance between satellites and constantly synchronize them so that no expensive atomic clocks would be required to provide GNSS capabilities. Since Starlinks are communication satellites they are also equipped with large antennas operating in the Ku and Ka band, in a region of the electromagnetic spectrum made up of waves of about 10-20 GHz frequency or 1-2 cm wavelength, these antennas could be used to broadcast the GNSS signals.
Since starlink V3 satellites are designed to orbit at 300km and they can focus their transmissions on a far smaller area compared to GPS satellites, the resulting signal could be more than a million time stronger, making jamming extremely impractical, especially since starlink has a lot of electromagnetic spectrum available in the Ku and Ka band, forcing a jammer to spread its power over a wide band.
The small wavelenght of the signals transmitted by starlink satellites is another element that improves jam-resistance since it enables the design of small CRPAs with many elements that can fit on the rear face of warheads.
Another advantage of this new architecture becomes apparent during reentry: the signal is strong enough that the plasma sheath would only block it only for a short amount of time. 10-20 GHz signals help here as well since higher frequency signals can more easily go through the reentry plasma, especially at the rear of the warhead, where it's less dense.
Datalink and moving targets
Starlink V3 satellites were originally designed for communications and there's no reason to not retain some of this capability. This could be used to redirect a warhead in flight to a new target of opportunity or to update the projected position of a moving target at time of impact.
This guidance method has the advantage of enabling cheap and simple warheads to threaten moving targets like warships but requires the target to be constantly tracked by external sensors with high accuracy, especially in the terminal phase.
This kind of global all-weather reconnaissance can be achieved with a large LEO radar satellite constellation.
Global reconnaissance and tracking constellation
Starlink V3 satellites could be modified into radar satellites as well. This might seem strange but radar and communication satellites do share a lot of features: both have large antennas capable of transmitting and receiving signals, the main difference is that a radar is designed to receive the transmitted signal after it's reflected by a surface while in a communication satellite the transmitted and received signals are largely unrelated.
Starlink V3 satellites have a number of features that make them very attractive radar platforms: the most useful is the low operating altitude of 300km (other radar satellites operate at more than 600km), since the strength of the reflected signal is inversely proportional to the fourth power of the distance this alone improves the performance of the radar by 16 times.
The large Ka/Ku band antennas are also capable of focusing a lot of radio power in a small area, increasing radar return but do have a weakness: radio waves in those frequencies are more susceptible to atmospheric absorption, especially in bad weather. This is the reason why ground based radars do not use these frequencies but it's less of an issue for a satellite based system where the radio waves spend less time in the thicker regions of the atmosphere.
Finally the laser links between Starlink satellites have a lot of potential here as well, enabling multiple satellites to synchronize their emissions and work together, significantly improving the performance of the constellation.
Defeating radar stealth
This would be especially useful to defeat stealth: radar stealth mostly works by deflecting incoming radio waves away from the direction of the emitter. This is extremely effective unless distributed and coordinated radar systems are employed: radio waves deflected away from one radar could be detected by another.
If many radar satellites emitting and receiving from many different directions work together, a 6th gen fighter wouldn't be much more difficult to detect than an unstealthy one. This is especially true since stealth planes aren't optimized to defeat radars in the Ka/Ku bands since it's unsuitable for ground-based radars.
Jamming resistance
This radar constellation, while extremely capable, is still vulnerable to jamming. However the high number of satellites and the wide bandwidth available to them means that jamming them all wouldn't be trivial. This is especially true since each jammer could only obscure an area of about one square km, meaning a large number would be needed to defend an area.
Another important fact is that while a jammer would be able to hide an area around it from observation, its emissions would be very visible to the constellation and could be tracked accurately enough for area-effect weapons to be dispatched to a jammer's location.
Conclusions
Constant worldwide radar reconnaissance and tracking and jam-resistant navigation and datalink provided by next-gen satellite constellations will revolutionize the ways wars are fought, especially if combined with the strike potential of reusable rocketry.
Controlling Low-Earth Orbit will be crucial in future conflicts, arguably more than air superiority is today.
This is why in the next article I'll discuss how to deny the enemy the use of orbit while protecting your own assets, especially from the debris generated by the destruction of thousands of satellites.
No comments:
Post a Comment