Sea Dart question.

[Mr.Creak]

I've just bought a very nice pair of Sea Darts in 72 scale from Fleetscale.
But...
They look like this:

Whereas most photos show them looking like this:


So are the fins on the booster some sort of "flip-out" mechanism and (more than double) their length on launch ¹, or are/ were there variants with longer booster fins?
Anyone know?

1 Looks pretty unlikely given the apparent thickness of those fins.

[Weaver]

Yes, the fins do indeed "flick out". They have a pivot at their lower leading edge, the lower part of the fin being thicker and more rigid to support it:

You can see the mechanism really clearly in this pic:



I'm not sure whether the orange rods in the pics are "actuators" of some kind or are just there to stop the fin from moving, since this is an inert handling round (you can tell by the red colour). They don't seem to be there on live (white) rounds, but I can't find a really clear pic. My impression was always that the fins were deployed by inertia during the violent launch acceleration, but again, a quick web search can't confirm this definitively.

Jusr had a look at Fleet Scale's site again, and the Sea Darts don't look over-accurate, having some very deep lines around the middle and a very vague representation of the booster fins.

[Mr.Creak]

Ah, thanks.
They "flip back" rather than "out".
It's so obvious now.

Agreed, the Fleetscale ones aren't perfect, but they're recognisably Sea Darts (or Mobile Land Darts by the time I've finished with them).

[Captain Canada]

Cool pics guys ! I guess that answers that question !

[rickshaw]

The second picture appears to be a practice round.

My understanding is that Sea Dart utilises the fins on the booster for rough course corrections during the boost phase.   While the ones on the practice round appear cropped, in this image of an operational missile launch, it is possible to see the longer fins:



This practice round appears to have longer fins:



I would suggest that perhaps the fins are either flip out or they changed during the life of the missile.

[Weaver]

Rickshaw: in your launch pic, you can see the fins in the folded-forwards position on the round that's still on the launcher. They deploy REALLY fast: I've only ever seen one pic that managed to capture them half-deployed, but I can't find it on the web.

The fins on the booster don't for steering as far as I'm aware, nor did they change design over the life of the missile.

[Captain Canada]

Wow....2 more awesome pics for the collection ! The one almost looks like a painting...and the other has a Sea King in it !



So the flip-out fins on the booster were just for stability ?

[PR19_Kit]

Whoever took that launch piccie was REALLY quick on the shutter button! Awesome nonetheless.

Visually there doesn't seem to be any scope for steering those booster fins in Weaver's close-up piccie, it looks as if the mounting is bolted securely to the big ring around the rocket exhaust.

[Weaver]

Wow....2 more awesome pics for the collection ! The one almost looks like a painting...and the other has a Sea King in it !



So the flip-out fins on the booster were just for stability ?

I think it actually is a painting, but it's based closely on several real pics, and as far as I can tell, it's very accurate. Lovely piece of work.....

Yes, I think the missile was essentially ballistic until booster separation. That wasn't very far mind you: the booster was there to get it up to ramjet ignition speed ASAP rather than adding range, so it burnt very hard and very fast. That minimum engagement range was one of the system's Achilles' heels if you were depending on it for your sole AA defence (which it was never designed to be, of course).

[Weaver]

Whoever took that launch piccie was REALLY quick on the shutter button! Awesome nonetheless.

Visually there doesn't seem to be any scope for steering those booster fins in Weaver's close-up piccie, it looks as if the mounting is bolted securely to the big ring around the rocket exhaust.

These videos show you just how quick:

http://www.youtube.com/watch?v=AKgQ-qwcs-s
http://www.youtube.com/watch?v=TJ3-2kwPZxQ

And this is what happens when it goes wrong:

http://www.youtube.com/watch?v=m29eTQTm0Ho

[PR19_Kit]

That misfire looked pretty darn scary! 

And I was standing right alongside Edinburgh's Sea Dart launcher only a month or so ago, the day before she finally paid-off. I wondered what the little right angled pipes were sticking out of the deck just aft of the Mk 8 turret were for. Now I know, they squirted cooling water all over the deck below the Sea Darts!

[rickshaw]

What surprised me was the lack of alarm in the sound track.  Very professional (or it was a more common event than we realise! ).

Those boosters put out a fair old whack of thrust it seems.  I'd be worried about an explosion from the fuel if a misfire occurs.

[Weaver]

What surprised me was the lack of alarm in the sound track.  Very professional (or it was a more common event than we realise! ).

British old boy! Stiff upper lip and all that! Running around and getting excitable is for the Yanks: they do it so much better than us.....

(Actually, I think you can hear someone say "shiiiit" quietly in the background, so it must have been really quite serious...)

[Logan Hartke]

Yeah, that looked very nasty.  On the topic of "getting excitable", I'm a bit odd in that I don't use profanity in my day-to-day speech.  I joke with my friends that it's because that way, I'll have something to use when things go REALLY wrong.  There are some people that you wouldn't know whether they spilled some water on their shirt or they just stumbled upon a dead body since certain words are so ubiquitous in their speech.  Me, however, you'll know things just got really bad when you hear words you've never heard me utter before.

Cheers,

Logan

[Weaver]

That's fair comment actually Logan. Personally, I find my speech adapts to those around me in all sorts of ways, not just swearing. I've got good friends who "eff and blind" if they stub their toe and others who you might just get a "damn" out of if faced with WWIII.....