Saturday, June 19, 2021

LEO SAR, hypersonics, and the death of the naval surface ship


Duh... Let's spend ~$10B each for new aircraft carriers that can be easily monitored from space and attacked using hypersonic missiles. 

Sure, in a real war with a peer competitor we'll have to hide them far from the conflict zone. But they're great for intimidating small countries...

More on aircraft carriers.

The technology described in the videos is LEO SAR = Low Earth Orbit Synthetic Aperture Radar. For some people it takes vivid imagery to convey rather basic ideas.

In an earlier post we described how sea blockade (e.g., against Japan or Taiwan) can be implemented using satellite imaging and missiles, drones, AI/ML. Blue water naval dominance is not required. PLAN/PLARF can track every container ship and oil tanker as they approach Kaohsiung or Nagoya. All are in missile range -- sitting ducks. Naval convoys will be just as vulnerable. 

Sink one tanker or cargo ship, or just issue a strong warning, and no shipping company in the world will be stupid enough to try to run the blockade. With imaging accuracy of ~1m, missile accuracy will be similar to that of precision guided munitions using GPS.

Excerpt below from China’s Constellation of Yaogan Satellites and the Anti-Ship Ballistic Missile – An Update, International Strategic and Security Studies Programme (ISSSP), National Institute of Advanced Studies (NIAS -- India), December 2013. With present technology it is easy to launch LEO (Low Earth Orbit) micro-satellites on short notice to track ships, but PRC has had a sophisticated system in place for almost a decade.
Authors: Professor S. Chandrashekar and Professor Soma Perumal 
We can state with confidence that the Yaogan satellite constellation and its associated ASBM system provide visible proof of Chinese intentions and capabilities to keep ACG strike groups well away from the Chinese mainland. 
Though the immediate purpose of the system is to deter the entry of a hostile aircraft carrier fleet into waters that directly threatens its security interests especially during a possible conflict over Taiwan, the same approach can be adopted to deter entry into other areas of strategic interest
Viewed from this perspective the Chinese do seem to have in place an operational capability for denying or deterring access into areas which it sees as crucial for preserving its sovereignty and security.
ICEYE, a Finnish micro-satellite company, wants to use its constellation to monitor the entire planet -- Every Square Meter, Every Hour. This entire network would cost well under a billion USD, and it uses off-the-shelf technology. 

It seems plausible to me that PLARF would be able to put up additional microsats of this type even during a high intensity conflict, e.g., using mobile launchers like for the DF21/26/41. A few ~10 minute contacts per day from a small LEO SAR constellation (i.e., just a few satellites) provides enough targeting data to annihilate a surface fleet in the western Pacific.

Added from comments
... you can make some good guesses based on physics and the technologies involved. 
1. Very hard to hit a hypersonic missile that is maneuvering on its way in. It's faster than the interceptor missiles and they can't anticipate its trajectory if it, e.g., selects a random maneuver pattern. 
2. I don't think there are good countermeasures for hiding the carrier from LEO SAR. I don't even think there are good countermeasures against final targeting seekers (IR/radar) on the ASBM (or a hypersonic cruise missile) but this depends on details. 
3. If the satellite has the target acquired during the final approach it can transmit the coordinates to the missile in flight and the missile does not have to depend on the seeker. On the Chinese side it is claimed that the ASBM can receive both satellite and OTH radar targeting info while in flight. This seems plausible technologically, and similar capability is already present in PLAAF AAM (i.e., mid-flight targeting data link from jet which launched the AAM). 
4. The radar cross section of a large ship is orders of magnitude larger than, e.g., a jet fighter. The payload of a DF21/26/17 is much larger than an AAM so I would guess the seeker could be much more powerful than the IR/AESA seeker in, e.g., PL-15 or similar. (Note PL-15 and PL-XX/21 have very long (BVR) engagement ranges, like 150km or even 400km and this is against aircraft targets, not massive ships.) The IR/radar seeker in an ASBM could be comparable to those in a jet fighter. 
I seriously doubt you can hide a big ship from a hypersonic missile seeker that is much larger and more powerful than anything on an AAM, possibly as powerful as the sensors on a jet fighter. 
On launch the missile will have a good fix on the target location from the satellite data. In the ~10m time of flight the uncertainty in the location of, e.g., a carrier is ~10km. So the seeker needs to find the target in a region of roughly that size, assuming no in-flight update of target location. 
Finally, keep in mind that sensor (both the missile seeker and on the satellite) and AI/ML capability are improving rapidly, so the trend is definitely against the carrier.

USN guy: We'll just hide the carrier from the satellite and missile seekers using, you know, countermeasures!  [Aside: don't cut my carrier budget!]

USAF guy: Uh, the much smaller AESA/IR seeker on their AAM can easily detect an aircraft from much longer ranges. How will you hide a huge ship?

USN guy: We'll just shoot down the maneuvering hypersonic missile using, you know, methods. [Aside: don't cut my carrier budget!]

Missile defense guy: Can you explain to us how to do that? If the incoming missile maneuvers we have to adapt the interceptor trajectory (in real time) to where we project the missile to be after some delay. But we can't know its trajectory ahead of time, unlike for a ballistic (non-maneuvering) warhead.

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