How effective is the Rapier (and the modded Sabre) engine at getting into Orbit?

[Osamaru]

I Like the consept of the Rapier, and the larger Sabre the parts mod Addes, but How effective are they at actually gettting into Orbit, vrs other methods? They seem pretty effective, However, even though their Stats stay their ISP is around 360-385 for Vacuum, it feels like they drain tanks really fast as well. Are they only good as Stage 1 engines?or is are they efficient enough to use for getting out of Orbit?

[HoloYolo]

No, thier ISP drops extremly low in vacuum and they destroy fuel.

[Osamaru]

Originally posted by SquidgyTunic:

No, thier ISP drops extremly low in vacuum and they destroy fuel.

That's what I was wondering, It seemed Strange, as the actually Tool tip showed about the same ISP as other sized engines. But as soon as the Air intake runs out, it starts to burn like mad. yes, I know it switchs modes, I mean It seems to burn it much quicker than others.
Now, that being said, I DO still have about a Third of a FL-T100 after getting into a 100km orbit with a small probe, so It feel like they are good for at least getting INTO orbit, But how they compare, if if they actually are fuel guzzlers, I can't seem to find.

[El Rushbo]

I've never actually gotten them to work right myself, however in my experience with SSTOs I've found the ideal scenario would be to build up enough speed on jet propulsion alone to fling yourself out of the atmosphere. Where then you'd require a short burn with rockets to achieve orbit. I'm thinking the RAPIERs extreme fuel consumption may be due to the fact that it has rather high thrust and the automatic switching changes over while still in the atmosphere. Nearly all my SSTOs rely on smaller engines that in some cases have lower ISP but with lower thrust as well so fuel would drain slower. In any case as far as reaching orbit it's best to not have to use your rockets until the last second.

[PKNecron]

Man, I LOVE the SABRE engines. I can get into orbit with tiny amounts of fuel compared to standard liquid rockets. I guess it comes from getting to 25KM on the jet then switching over to the rocket. Throw on a couple of solid boosters and it's even easier. The Rapier isn't half as good as the SABRE though.

I was actually starting to think of them as cheating...

[PKNecron]

A very hasty and crude example: 2 rockets.

http://steamcommunity.com/sharedfiles/filedetails/?id=388922658
Put this one into a 90K orbit on the first stage with fuel left using the SABRE M engine x 2.

http://steamcommunity.com/sharedfiles/filedetails/?id=388922772
Same payload and same fuel load using conventional rockets. Entered orbit having jetisoned the first stage and used 1/3 of the orbiter's fuel.

Both rockets had roughly the same thrust sans boosters. 1400Kn.
Both work, the SABRE engines are more fuel efficiant and the conventional rocket is cheeper.

[Osamaru]

What's the Duel Connector Called? I remember seeing it, but can't find it now.

[PKNecron]

I refined the design a little bit.

http://steamcommunity.com/sharedfiles/filedetails/?id=388931896
Same payload. One SABRE M and 1/2 the fuel of the original. One stage to orbit. Cost roughly 3k more than the conventional rocket. Now, it's slow getting up there, but it is very effcient doing it.

Originally posted by Torigoma:

What's the Duel Connector Called? I remember seeing it, but can't find it now.

Under structural TVR-200. There are two three and 4 pod versions. BTW I had to use tweakscale to get the engines to fit as the TVR-200 is 1.25 M scale and the SABRE M is 2.5 M.

[PKNecron]

Oh, and I forgot to mention the payload is 11.665 tons.

[PKNecron]

Final design:

http://steamcommunity.com/sharedfiles/filedetails/?id=388946663
Only change is adding more air intakes. 16 more to be exact. Going from 8 intakes to 24 did one thing. It meant that my SABRE switched over to rocket mode LATER in the flight. With 8 intakes it switched modes at 27km. At 24 intakes it switched at 34km. This translates to 11 seconds more burn time with the main stage once in orbit. For a 1100% increase

[Osamaru]

Ya, I'm still fiddling around with how Air intake works with it myself .

[PKNecron]

Originally posted by Torigoma:

Ya, I'm still fiddling around with how Air intake works with it myself .

I find that intakes are NOT linear in progression. From 8 intakes to 16 I gained about 4500 metres before mode switch, but from 16 to 24 I only gained an additional 2500 metres.