How do missiles like SS-N-Siren follow terrain?

[ExMachina]

Just occurred to me that anti ship missiles (like the Siren) are following terrain (over fjords and islands) with superb precision even if they have no active sensor to detect what was in front of them.

Is this model correct?

[Dimitris]

Most cruise missiles have a radar altimeter (separate from their search sensors) that enables them to stay at a near-constant AGL (not barometric) altitude. This should suffice for most terrain slope gradients (barring e.g. a vertical cliff coming up).

[ExMachina]

Thanks. So CMANO assumes that all SSMs have this capability?

In any case, the instantaneous altitude changes for all SSMs seem impossibly fast and certainly doesn't allow for hiding ships immediately behind sharp drops in elevation. And as you mention, severe terrain elevation increase (like cliffs) don't sees to phase it either and the missiles zip up and over and never crash.

[starbird7]

Radar altimeters were were in use during ww2.

Wikipedia mentions that the SS-N-7 was the first to be fitted with a radar altimeter and entered service in 68.

It looks like earlier missiles used a mix of datalink (radio commands) and INS.

[ExMachina]

The The Naval Institute Guide to World Naval Weapons Systems says the SS-N-9 Sirens had a barometric altimeter only. But that's academic and if CMANO wants to generalize radar altimeters that seems very reasonable (after all, how many naval surface engagements are fought across intervening islands)

That said [;)]...more realistic climbing and diving for SSMs would go a long way to at least allowing small fast boats to duck into coves/fjords to sometimes evade incoming vampires.

[CV60]

Jane's Naval Weapons says that the SS-N-9 had a radio altimeter

[ExMachina]

This document agrees with Janes. However, it says the Styx only had barometric altimeters (which is also the opposite of what The Naval Institute Guide says...)

[&:] [:D]