Rapier disappointment

[miklkit]

I just got the Rapier and thought that now I could really go places. Wrong! It can't get to altitude or speed so ends up using as much or more fuel than the Whiplash so the effective range is the same. It can only make it to the Mun.
My best SSTO uses whiplash for low altitude, Cheetahs to get into space, and a NERV from there.
This is the Rapier rig after landing on the Mun. It ran out of fuel about 40 meters from the ground but the only damage was the nerv getting knocked off.
https://steamcommunity.com/sharedfiles/filedetails/?id=2130508161
This is my current best performer.
https://steamcommunity.com/sharedfiles/filedetails/?id=2130519898
I thought the Rapier could combine the Whiplash and Cheetah for a weight savings, but the poor performance just kills it. Is this the way it is or am I missing something?

[Rhomphaia]

The trick to the rapier is getting up to speed first. Soon as you're off the runway level out until mach 1, then slowly climb to altitude.

[Катя Мяу <3]

Agreed. The Rapier is a disappointment. It works well for smalller passenger ships flying within the Kerbin gravity well. But once you get heavier and want to get some payload into orbit, it just doesn't cut it anymore.

[GunsForBucks]

I found the Rapier seemed best for very high altitude sustained flight +20k

Getting there or going past is pretty bad at least how I tried to use it.. gave up on them honestly.

[Vectura]

Rapier can still work for bigger stuff for LKO. Made an SSTO spaceplane that could get about 32 tons to orbit with a bit of fuel spare to deorbit.

[miklkit]

Originally posted by Rhomphaia:

The trick to the rapier is getting up to speed first. Soon as you're off the runway level out until mach 1, then slowly climb to altitude.

That's a trick all right as they do neither. My launch method now is to take off and fly low until it hits top speed, then turn on the nerv to push it up to speed and altitude. Turn off the nerv and it climbs into space well. Nerv it to the Mun and land with Rapiers, refuel, and go on my way.

I have zero interest in LKO. It is Mun or bust.

[Manwith Noname]

If you can't hit mach 1 at low altitude then you've got problems.

Edit: If you've never seen them, the performance charts can be useful...

https://wiki.kerbalspaceprogram.com/wiki/Template:Stats_table_jet_engines_-_curves

[miklkit]

I never knew that mach 1 was 300 m/s. I replaced the Whiplashes with Rapiers on this one earlier today and it hit 310 m/s before I gave up, fired up the twin Cheetahs and pointed the nose up. It can make LKO but nothing more.
https://steamcommunity.com/sharedfiles/filedetails/?id=2130781349

[Катя Мяу <3]

Originally posted by miklkit:

I never knew that mach 1 was 300 m/s. I replaced the Whiplashes with Rapiers on this one earlier today and it hit 310 m/s before I gave up, fired up the twin Cheetahs and pointed the nose up. It can make LKO but nothing more.
https://steamcommunity.com/sharedfiles/filedetails/?id=2130781349

You are not even at 50% throttle, thats why.

[MechBFP]

Originally posted by ֺ:

Originally posted by miklkit:

I never knew that mach 1 was 300 m/s. I replaced the Whiplashes with Rapiers on this one earlier today and it hit 310 m/s before I gave up, fired up the twin Cheetahs and pointed the nose up. It can make LKO but nothing more.
https://steamcommunity.com/sharedfiles/filedetails/?id=2130781349

You are not even at 50% throttle, thats why.

Roflmao. They have likely been playing the entire game at half throttle. Amazing.

[miklkit]

I should have stated that that screenie was taken while gliding in for a landing. Notice the fuel level.

Here is a different I was playing with. This is how far it got before it ran out of gas because it burned it all up getting up to speed.
https://steamcommunity.com/sharedfiles/filedetails/?id=2130919632

[Vectura]

Also make sure you slightly reduce how much oxidizer you are taking, and use the rapiers in liquid fuel mode. For my ssto that uses them, I gain as much speed as I can without overheating at sea level, then begin a fairly gentle climb. At somewhere around 15km I start to go a little steeper, but not much. Barely need to do a circularisation burn as the ascent is shallow.

[Azunai]

rapier top speed in air breathing mode is about 2-300 m/s higher than the whiplash and it shuts off at a higher altitude, that's all there is to it, really.

judging by your screenshot you must be doing something wrong. you should squeeze out about 1500+ m/s from a rapier in airbreathing mode.

the rocket mode of the rapier is pretty meh. it's ok for stuff that only needs to get to orbit. you save the extra mass of a dedicated rocket engine which more than makes up for the rather low Isp.

for anything that needs to go further you'd be MUCH better off bringing nuke engines instead of slightly more efficient lf/o rockets.

[Rhomphaia]

>Mach 1
https://steamcommunity.com/sharedfiles/filedetails/?id=2131173978
>mach4 still airbreating
https://steamcommunity.com/sharedfiles/filedetails/?id=2131174001

The nose is never more than 10degrees above the horizon until I switch to closed cycle and fire up the NERV, use the closed cycle to get apoapsis above 55km and time to apoapsis to 1m30s, the NERV can take it the rest of the way to orbit from there. 3000m/s left on orbit.

A Mun landing would be challenging since I don't have any spare Ox for the Rapiers, but the NERV will have a Mun TWR of around 1.8 when it gets there so should be doable, Minmus is a cakewalk.
The plan for this plane was to land tourists on minmus then orbit Mun and dock with a station that has its own lander then return to Kerbin all without refuelling.

[miklkit]

I can get the Mark 1 ssto to the Mun ok with either whiplash or Rapiers, but the Mark 2 are barely good enough to get to orbit.
The mk 2 has to stay low until it hits its max speed. Then I hit the rockets and aim it a little up until it gets over 8000 meters where I level it out to get more speed. When it goes over 1300 m/s I aim it up for space.
This goes for all the versions I have built so far from so small they run out of gas to 60 ton 6 engine monsters. Because of the need to fire the rockets at sea level they are using aerospike motors now as they are better at low altitude.
Maybe I'll just go back to whiplash motors as they get up to altitude much better.

[Azunai]

you don't need to fire the rockets at sea level. rapiers work just fine all the way from the runway to ~28km altitude.

if you have to toggle rocket motors to breach the sound barrier, you either have a broken installation of the game with some screwed up aerodynamcs or your planes are literally bricks with wings.

but the plane on the screenshot you posted earlier looks ok, so i guess that your game installation is broken or one of your mods messes with the game in the wrong way.