The Debate of Solid vs Liquid

[MaverickSawyer]

I'll chip in with my two cents...

 

The two types of engines have their followers and detractors in equal measure. And I think that @YNM hit the nail on the head here... the decision making process often falls down to what I'll generously describe as "cultural differences".

 

That said, there are certain things that each type of engine, in my opinion, is better for...

Solid fuel: Storability for extended periods; high thrust over short durations

Liquid fuel: precise control over throttle settings and total impulse; efficiency

[YNM]

Yeah.

One good thing with solids is that the casing around it would rot before the fuel degrades.

[DerekL1963]

4 minutes ago, YNM said:

One good thing with solids is that the casing around it would rot before the fuel degrades.

Not quite true.  Solids can last a long time, but not indefinitely.

[YNM]

11 minutes ago, DerekL1963 said:

Not quite true.  Solids can last a long time, but not indefinitely.

It's just a notion.

[DDE]

On ‎14‎.‎04‎.‎2018 at 7:00 AM, YNM said:

You can't load solids on liquid engines, and you can't put liquids in an SRB casing.

Curiously, RMI was asked to develop a drop-in hydrazine-NTO replacement for the solid motor on the Sparrow III missile, and they succeeded. They did end up with the design scrapped (because Thiokol finally made a freeze-proof design), although they managed to get the Bullpup fielded instead.

One thing that you lot have all missed is the matter of size. Liquid fuel means less size per dV, and it's possible to squeeze tankage into every part of the missile imaginable. This is why Makeyev, the Soviet SLBM guys, are liquid fuel fanatics. That one time they were forced to do a solid-fuel missile, they still came up with a liquid second stage; the other time, the result was the Typhoon submarine and its greatly maligned monster missiles; so for the highly cntroversial Bulava, they had to be booted in favour of the Topol developers, who specialize exclusively in solids. Instead, they were to design the Sarmat, and guess what that thing uses:

 

[YNM]

1 hour ago, DDE said:

drop-in hydrazine-NTO

Wow. Does it use balloon tanks or something (presumably it doesn't need to be as strong) ?

[wumpus]

7 hours ago, DDE said:

Curiously, RMI was asked to develop a drop-in hydrazine-NTO

Do you really want to be in a confined environment with multiple large tanks of hyrdazine and NTO?  I'd imagine there are enough things that can go wrong in a submarine without bringing something like that aboard.

[DDE]

3 hours ago, wumpus said:

Do you really want to be in a confined environment with multiple large tanks of hyrdazine and NTO?  I'd imagine there are enough things that can go wrong in a submarine without bringing something like that aboard.

Performance justifies all.

Energomash developed the RD-503 as an upgraded first-stage motor for Sineva. It's the one Soviet engine I know of that was built for chlorine pentafluoride.

[DerekL1963]

7 hours ago, wumpus said:

Do you really want to be in a confined environment with multiple large tanks of hyrdazine and NTO?

Soviet submariners were not volunteers, and had little choice in the matter.  I don't know about Russian practice.

But also keep in mind that the birds are confined to and isolated in their launch tubes.

[kerbiloid]

5 hours ago, DerekL1963 said:

Soviet submariners were not volunteers

They were appointed volunteers.

[MaverickSawyer]

Voluntold.