Jammability of military data links

Factual Questions
1

In the past, some of my questions left posters puzzled since I only gave the precise questions I wanted an answer to without mentioning the context. The double fairing question is a good example. Once I described the context, my question was more readily understandable. I’ll do that here.
I’ll give context-less questions first then if you want the context, read on:

  1. How easy are military data links to jam, spoof or generally disrupt?
  2. Is the jammability of data links the reason that track-via-missile guidance is little used compared to semi-active radar homing? If not, why is it little used, given the potential for lower cost and greater precision than SARH?
    3.1) Is it also the reason that using the missile to transmit while the launching platform receives, processes and sends commands via data link hasn’t been used? It would offer two advantages: 1) The launching platform could remain passive except for a data link which would have a lower probability of intercept than transmitting tracking and guidance beams 2) As the missile got closer, its angular accuracy would increase and the amount of energy reflected off the target’s skin would be greater than if the launching platform transmitted which would make jamming more difficult.

3.2) Would the missile’s engine/motor be usable as a power source for the transmitter?

Context:

Data links are particularly important in naval and aerial warfare. I will list some data link-intensive methods which might be useful.

  • Using lower frequency, even going as low as S or C band for a fighter, would increase range and impede enemy stealth. Lower frequency has the downside of lower resolution. However, several radars each transmitting in low frequency from widely space azimuths would create a synthetic aperture antenna which would have greater resolution than the choice of lower-than-X-band frequency would suggest.

  • Having several platforms transmit and receive would create a multistatic radar system which would impede enemy stealth and jamming.

  • Multistatic radar would allow some platforms to only receive while other platforms only transmit. The receive-only platforms would be stealthier. The transmit-only platforms could use frequency modulated continuous wave (FMCW) which would provide good range, great velocity resolution and low probability of intercept (LPI). The transmitters and receivers could alternate roles to make them more difficult to track and engage.

  • Widely spaced platforms could passively fix enemy location and perhaps velocity based on its transmissions.

  • By comparing the received signal of several platforms, receiver noise would be easier to filter out. This is because receiver noise is specific to each receiver: hence, false targets caused by receiver noise are unlikely to be shared across receivers and thus easy to filter out by comparing the data input from several receivers. This would make it possible to crank up amplification while maintaining the same constant false alarm rate.

  • It would be possible to launch missiles from submarines, ships or aircraft which stay below the enemy radar horizon and rely only on data link to acquire and engage targets. Perhaps missile guidance could use multiple LPI FMCW transmissions or data link.

Most of these methods require heavy processing. Such processing is best done using powerful computers. Ships have the room and electricity to operate powerful computers. They also have greater anti-air/anti-missile assets and general survivability than aircraft. Ground-based processing is also possible.

Early airborne warning (EAW) planes can act in their primary role but also as intermediary processors and data relays. An EAW plane flying at about 10km altitude and fighters flying at the same altitude would have a radar horizon (and presumably data link horizon) of about 800km. If not, having the fighters fly at 15km would produce an 800km visual horizon. Data links of that distance and at that altitude might be possible given that atmospheric attenuation decreases severely with altitude.

It would also be possible to station one EAW plane above the data-processing ship/ground station and daisy chain EAW planes to extend the data link range further.

We might see a change in frequency choice where search, track, guidance and data link share the same frequency bands depending on the means available.

As you can see, data links are useful and so would their disruption.

So, that’s the context of my questions.

2

Those who know won’t be telling.

3

I wouldn’t say that TVM is little used. Any command guidance system (including TVM) requires a more complex launching platform than SARH. So you would only expect to see it in long-range expensive SAM systems. Patriot and S-300 use TVM, US Navy Standard missiles do not.

Missile transmitter is very very weak. ARH can typically only detect a target at 10-20km range.

I am not sure how this would work. Also, rocket engines typically burn out long before the terminal phase.

4

I’d guess that most military communications are done using some sort of encrypted, packet-switched network transmitted via some kind of frequency hopping spread spectrum method.

That’s pretty hard to jam. It can probably be done, but it’s probably more of a brute-force method than anything else.

5

How could the launching platform increase in cost/complexity so much that it doesn’t to make up for the fact that it can be reused whereas missiles destroy their processors every time they’re fired?

If a platform has four SARH missiles, it will need 4 processors. If it has 4 TVM missiles, it needs one processor which was already present in the platform’s radar system.

I can’t a priori reject the possibility that it would end up being simpler/cheaper to use SARH than TVM but I don’t really see how.

Since ARH transmitters are weak, are they easier to jam/spoof than SARH?

Are there any misconceptions in the context segment of the OP?

6

Command guidance requires that the launching platform concurrently tracks both the target and the missile. This used to require two independently steered radars (hence extra cost), plus a datalink to the missile. With a modern ESA radar, you can use one antenna.

AFAIK, the idea behind TVM is primarily to defeat ECM. You can use a sophisticated computer / human operator in the launcher to differentiate between true and false targets. TVM missiles generally switch to SARH homing for terminal phase anyway. The latency makes it difficult to guide the missile into a highly agile target using only the ground commands. Thus early missiles like Nike Hercules or S-75 (which didn’t have SARH mode) had a very large warhead to compensate.

TVM missiles were an answer to technological limitations of 1980s. With modern missiles the older distinctions are moot. A modern missile will have a radar with active/semi-active/passive modes, powerful on-board computers, and a high-bandwidth datalink that can transmit everything the missile is seeing.

Yes, but not really because they are weak. ARH missile at 10km from target will receive the same return signal as a big engagement radar 100km from target. Spoofing is about fooling the computer logic, and missile will always have a much simpler programming than the launcher.

7

It is very difficult to hide a stationary radar. The various techniques you mentioned work well for aircraft, which need to be tracked continuously. But stationary radars do not. SAM search radar needs to transmit 24/7 to be effective. It may take a few minutes or a few hours, but its position will be triangulated with sufficient precision to send in a missile (one with optical or active terminal homing).

Synthetic aperture radar requires both multiple antennas, but also a very high bandwidth datalink between them. The processor needs a very tightly synced raw feeds from all antennas. In practice, you would need to connect then with optical fibers. Easy enough for a national AD system, difficult with mobile units in the field. It would be interesting to see what could be done with re-purposed cellphone towers.

EAW plane is a very juicy target!

8

AdamF,
You mention more recent missiles having a broad range of options for guidance. Do you know if anti-ship missiles (which presumably have active guidance and good processors) are capable of jamming/spoofing CIWS and anti-missile missiles? Messing with their radar gates or adding a jittered pseudo-echo for a few seconds might be all that’s needed to allow the anti-ship missile to close the distance.

EAW planes as juicy targets: Indeed. That’s why they’re usually kept behind fighters and only reachable by cruise missiles, right? I presume some thought and means have been put into preventing EAW planes from being shot down.

SAM missiles: What you say is certainly true for stationary transmitters. However, one option is to have stationary receivers (who become transmitters for launching) and alternating mobile transmitters for search. If transmitting can be done with cheap hardware, it’s possible to have decoy sites to set up ambushes.

Or just alternating mobile transmitters/receivers. Although, the latter option would make it difficult or impossible to use fiber optics.

9

Effectively jamming RF is pretty hard. I guess if one had the resources, you could transmit a wideband signal(s) within the frequency range, that was filled with nothing but noise. You’d effectively raise the noise floor and decrease their range. But, only for those that were close to you. You would require a significant amount of transmitters, all within the intended frequency range, “jamming”.

The best way might be to put the jammers half way between you and them. Over a large enough area to have the missile/whatever go into fail-safe mode. But, they could just navigate around said area but that would decrease the overall effective range.

10

I see that the AIM-9 Sidewinder’s more recent versions are able to launch and be guided by data link toward the target and only then lock on to it. This could prevent the target from ever realizing it’s been engaged.

It only has a range of 35km though. Would it be quite difficult to have a long range (100-300km) missile that uses the launching platform’s tracking radar to close in to the target until it’s close enough for the IR seeker to detect and lock on to the target? IR has limited range compared to radar but with a data link, it can combine IR and the launcher’s tracking radar.

Electronbee,
Fail-safe mode? What does that mean when it comes to missiles and radars?

11

This is a bit confused.

From the beginning, the AIM-9 was/is a pure IR-guided missile. As such the pre-launch tracking and all inflight tracking is 100% passive. As such there is no possible way for any target to detect that it’s being targeted pre-launch. Once the missile is launched the target still has no way to detect the fact its being tracked. a target could, in principle, use active radar to recognize that something is headed towards it, but that’s true against any missile regardless of guidance system.

The typical way an AIM-9 was/is used however is for the attacking aircraft to first illuminate the target with radar energy. Which the target can detect. This gives the attacker useful info like range, relative speed, etc. Which helps ensure the attacker shoots a good shot, not an out-of-range shot.

Typically in pure IR attack mode the missile “looks” straight ahead and to lock it onto a target you have to point the attacking aircraft directly at the target and maintain that alignment for a couple seconds. If the attacker is using radar he/she can slave the missile seeker to the radar’s look angle and lock onto a target while not pointed directly at it. This off-boresight capability has many advantages for setting up a favorable intercept and becomes uber-valuable once in a swirling fight.

Some aircraft have an IRSTS, essentially an IR scanning telescope attached to the aircraft. This typically has better range and sensitivity versus the missile’s seeker. This too can track a target and provide angle slaving commands to get the missile’s seeker looking at the right spot. Compared to radar, IRSTS has the advantage of being undetectable by the target, but the disadvantage of not providing any range or closure info to the attacker.
In any case, traditional AIM-9s had to have the missile see, and lock on to, the target’s IR source before launch. Once the pilot had confirmation the missile’s IR seeker was tracking the correct target he/she would launch. From then on the missile will autonomously chase the IR source until it fuzes.

The innovation you’re talking about was brought about by stealth. The F-22 & F-35 carry missiles in internal bays to maintain stealth. The traditional AIM-9 design can’t shoot unless it can see the target before launch. The way to square that circle was to provide a very short range / short duration data link that lets the missile be launched blind and then immediately be told where to look to see the target IR source. Once it sees the source it operates like a traditional AIM-9 and autonomously chases the source until it fuzes. If it doesn’t find the source pretty quickly, it “goes stupid” and is effectively a dud.

12

Predominantly the Sidewinder family has been a passive guidance system. The active data link doesn’t make the infrared package any less passive. It looks like it was part of extending the range. The data link is used in a variant where it’s a passive seeker. The missile doesn’t need to “see” the target’s signature at launch which is presumably harder the further out the target is. If you have the lock at launch the missile is passive from the time it starts it’s run.

13

I am not aware of anti-ship missile using jamming. It is certainly possible, but would it be useful? I am not sure. Incoming sea-skimming missile is a very simple target. It’s coming almost straight for the radar, so you have nearly constant azimuth and elevation readings. The range is changing in a predictable fashion and it also doesn’t matter too much (the autocannon has a fairly flat trajectory).

EAW planes: AFAIK, everybody is hoping that nobody will develop long-range AA missiles that could take down their EAW planes from beyond the horizon (about 400km).

14

LOAL was developed much earlier. In 1980s, Soviet R-27T could be launched without lock-on and would fly in straight line until it found a target (or hit the ground). In 1990s, ASRAAM and MICA IR got the capability, so that they could be launched at a fighter that is chasing you.

15

The catch there is that those extremely long-ranged AAMs are effectively small aircraft themselves and vulnerable to being shot down.

The US did have a 400km AAM back in the 1960s for nuclear bomber defense.

16

The Association of Old Crows is still around.
Their Journal of Electronic Defense was a gas to read back in the mid-80’s.
Not sure if Joe Blow can subscribe nowadays.

17

Quite. But that wasn’t what the OP or I was talking about. He wanted to know about AIM-9X’s datalink & LOAL feature.

18

Yes, I did a bad job of explaining what I meant.

As you said LOAL is chiefly useful if the missile must be retained within the aircraft until launch. I suppose that’s also why the small diameter bomb was developed; If you only have an internal weapons bay, you better pack many bombs in it.

First some premises:
IR is advantageous in that it can detect and track passively, unlike most radar guidance.

IR has the downside of low range because its 300 GHz to 430THz frequency range is quite high and attenuates readily in the atmosphere. IR missiles tend to have rather short range.
Usually, anti-air missiles are either long range or passive but not both. Anti-radiation missiles can be both but those require the target to be transmitting.

If the launching platform could track the target with radar and use data link to steer an IR missile* until the missile is close enough to rely on its IR seeker, the missile would be long range and passive. This combination could be quite advantageous.

The target would know that it’s being tracked by a platform but wouldn’t be able to tell if it’s been engaged and that, at ranges of 100km+. Are there non-radar homing anti-air missiles that can do that combination?

  • A missile with more propellant than the AIM 9. At 35km range, it’s not bad but nowhere near the upper end for SAMs and AAMs.

On another note, might a smaller version of the Oerlokin gun mounted on a fighter be useful for dogfights and CAS?

Quick summary: it’s programmable fuse shotgun shell.

Longer description:

http://www.aiad.it/aiad_res/cms/images/Oerlikon_Ahead_35mm_munition_d0.jpg

This particular one outputs 2533 projectiles per second.

Range-wise, it ought not be that difficult. Replace rocket propulsion with turbojet or small rocket booster+ramjet and you have enough range to get to the EAW plane in a package that’s light enough to be carried by a fighter. It’s extremely likely to be transmitting strongly too and it’s a critical target that’s expensive and must have crew that is difficult to replace. Even if the missiles costs 1 or 2 million dollars, it’s worth it if it gives you a good shot.

So, what are the difficulties in developing and using anti-EAW missiles?

19

[ul]
[li]Fighters settled on 20-30mm cannons as optimum. If smaller projectiles were effective, the US would still be using .50" machineguns.[/li][li]CAS needs both cannons against vehicles, and rifle-caliber machineguns against exposed infantry. Perhaps this would be a good compromise. I could really see it used by Mi-28. It already has the radar needed to properly time the fuse, and the 2A42 cannon has dual ammo feed (so you don’t sacrifice anti-armor capability).[/li][/ul]

20

Money.
Developing any new missile is expensive. And according to wikipedia, there is only about 250 EAW planes worldwide. Russia and China would be in the market for perhaps 100 units, India could presently use about 50. When you spread development costs over such small production, the unit cost will be sky-high.