Saunders-Roe SR.177 (P.177/F.177)

[overscan]

From a Saunders-Roe brochure for Germany....

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More.

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Last for now

[Captain Canada]

Hey, that's some pretty cool stuff ! Sure is a lovely looking aeroplane. One of these days, I'm gonna get me that kit !

Thanks for posting that !

[Daryl J.]

Saro aircraft like this are just so cool in a bulldog sort of way.    What are there in way of kits of these?



Daryl J.

[overscan]

Freightdog do a resin kit.

[GTX]

I'm awfully tempted one day to attempts a large scale (1/48 or even 1/32) scratch build of this - thanks for the info.

Regards,

Greg

[Weaver]

Gawd what a misuse of a pure interceptor for ground attack! Was it supposed to have it's HTP tanks fuelled on these missions?

[overscan]

Brochure has emergency ground attack role, which has limited range due to retaining the HTP tanks and rocket, and full ground attack role where the rocket is removed and HTP replaced with additional kerosene.

[dy031101]

I recall seeing the relevant entry within the BSP book stating that there were two competing rocket motor designs before the P.177 came along.  Would someone shed light on what led Saro to choose the Spectre over the Screamer?

[Hobbes]

I've checked Project Cancelled; this doesn't mention the reason Saunders-Roe chose the Spectre. Initially, the SR.53 was to have a rocket designed by SR themselves. When that design was deemed to take too much time to develop, SR went to the Spectre.

The MOD issued specification F.137D which led to the Avro 720. F.137D specified the use of the Screamer, in order to have an alternative design ready should HTP rockets turn out to be unsuitable.

Barry Jones' British Experimental Turbojet Aircraft has more info: SR's chief designer, Maurice Brennan, favored HTP, so that was chosen as the fuel for their own rocket. SR then found out that de Havilland Engines was getting similar performance from the Spectre that SR were seeking for their own design, and as de Havilland was further along SR chose to use the Spectre.
This book also mentions that the RAE favored a LOX-based rocket mostly because it would be much cheaper, but that "operational requirements ruled out the use of LOX". It doesn't say which requirements those were, though.

[Weaver]

Both LOX and HTP are seriously nasty stuff, but in different ways. HTP is corrosive and can spontaneously react, with extreme violence, in contact with a wide range of substances (the reaction's so violent you can use it as monopropellant!) LOX needs refrigeration to very low temperatures which complicates matters and is inherently dangerous, plus pure oxygen will make any fire much, much worse if it escapes.

Apparently the Admiralty were more concerned by the risks of LOX on a carrier than those of HTP, though that might be because more work had been done on HTP at the time, so the risks and procedures were better understood. Both the RAF and the RN also disliked the Screamer because it used "three fuels not two", though I've never properly understood that. It seems to have used water as well as fuel and oxidant, but I don't know what for or why....

Personally, if I had to have a rocket-interceptor (and I'd fight tooth and nail not to have one) then I've always preferred the idea of a LOX/kerosene rocket with the LOX carried in an external tank(s) that can be replaced by more jet fuel if required.

[rickshaw]

The major advantage from using HTP over LOx is that HTP rockets will continue to fire, even after the fuel has run out.  HTP rockets work by catalysing HTP through a metal grid (IIRC, silver oxide but I could be wrong) and this turns to Oxygen, steam and heat.  The heat combusts the mix of Oxygen and Kerosene.  However, if the Kerosene runs out, the engine will keep running, providing some thrust from the steam and Oxygen alone.  This actually caused some problems with the various British experimental rockets such as Black Knight when it was used to test re-entry vehicles for ICBMs.  The residual thrust prevented proper separation from the booster, causing the "shot" to either fail completely or be only partially successful.

[kitnut617]

As we're talking about rocket motors, there's a photo in the latest Aeromilitaria (Summer, June 2011) of the underside of EE P.1B (XA847) as it turns away from the camera ship with it's attached 'twin' rocket pack at full chat ---. In this case it's a Napier Double-Scorpion.  This would seem to be an excellent subject choice for Colin (Freightdog) to do -- hint, hint 

[pyro-manic]

Would that be this pic?



Lovely shot it is indeed.