Rapier in 1.0.2 completely useless

[Red Iron Crown]

So do I! please don't take it the wrong way. My comment was merely a slightly OT aside regarding the problems of transonic a/c design IRL.

(suggest anyone unfamiliar with the early F111 have a google "F111 boundary layer splitter")

No worries, I didn't take any offence.

I wasn't aware of the F111 intake thing, that made for an interesting read this morning.

[zarakon]

Also, in what case would jets + aerospikes be a good option? The aerospikes are extra extra heavy just so they have extra ISP in the lower atmosphere, and the lower atmosphere is exactly what you are 'skipping' (in rocket flight) when using air-breathing engines... So in that case the aerospike offers no advantages over the LV-Txx engines and only extra weight...

Aerospike is 1.5 tons now, just like the LV-T45. It has 20kN less thrust and no vectoring, but also 20 higher vacuum Isp.

The Aerospike also has a bit less drag

[Starhawk]

In my career game, Jeb is chief pilot for the aerospace division. He looks longingly at the end of the tech tree and those shiny Rapiers, but that's still a long way off.

So he does orbital rescue missions with a Whiplash + 2x Terrier combo (turbojet + 2x LV-909). It works, but the Rapier is vastly superior.

If you are close to the limits of what the Rapier can do mass-wise, the flat spot in the power band is very significant. But, I've found that if you back off pushing the mass limits just a bit, the Rapiers can blast through the flat spot almost without noticing. Besides, overpowered craft are more fun to fly!

Happy landings!

[rtxoff]

Well i did some more tests and the Rapier just doesn't work for me. I managed to get a somewhat small SSTO airplane with 2 Rapier engines into LKO. However the payload fraction is useless.

I don't know how all you guys manage to have high payload fraction with them it certainly does not work for me. To avoid misunderstandings, i am talking about the stock game without any mods at all. I don't know about FAR and other mods but in the stock game they are almost useless. As soon as i switch to turbojets and one aerospike i get much more efficiency even with the addional weight of the Aerospike with 1.5t i am also able to put a small payload into the plane which i can't with an Rapier only configuration.

Reading some of the posts here i really ask myself if you guys use the same engine as me? Can you all please verify your game files in Steam? I know that some people had problems where some parts did not get updated.

[KerikBalm]

Great words but obviously you didn't even try to make an SSTO plane with an LV-Txx and 2 turbojets. I would really love to see your airplane in action on 1.0.2 with such an configuration. Of course if you cheat everything is possible.

Its really really really easy to get to orbit with 2x turbojets and an LV-T45.

https://www.dropbox.com/s/k2sm739dkhddr0u/Rescue%20SSTO%20mk2.craft?dl=0

I'm pretty sure that's the right craft file... should get you into orbit with a nice bit of fuel to spare. Its just my small sat launching SSTO with a FL-T400 tank thrown in the cargobay for extra dV for rescues (Unlike some of my other craft that will take payloads to Mun and Minmus, this is an LKO only craft without refuel).

If you can't get that to orbit, then it is your piloting that is the problem. Perhaps your designs would work too if flown better.

[rtxoff]

@KerikBalm, yes by now i already tried that and you are right. It works however you won't save any weight with the T45 over the Aerospike like chris claimed.

Also at the end you will have more fuel left with the Aerospike because of better efficiency.

[Red Iron Crown]

gpisic: My game only has info mods, nothing modifying physics or parts at all. I detailed my ascent profile in another post here (craft file is there, too), perhaps you're using a different profile that doesn't work as well with RAPIERs?

[Mister Dilsby]

In my career game, Jeb is chief pilot for the aerospace division.

Funny, I arrived at exactly the same decision given two badS pilots in the roster. Jeb is the cocky fighter jock who drives atmospheric craft to an inch of their limits, Val the coolly confidant interplanetary savante.

[Starhawk]

Funny, I arrived at exactly the same decision given two badS pilots in the roster. Jeb is the cocky fighter jock who drives atmospheric craft to an inch of their limits, Val the coolly confidant interplanetary savante.

That is funny. I like that this maintains Jeb's mythos. Spaceplane success is so much about piloting now! In 0.90 you had to understand the ascent profile, but the magical turbojets were pretty forgiving. Now, if the ascent profile is off by even a few degrees, or the timing is off by even a little, it can result in 'not going to space today' or even absolute disaster.

On topic...

The hardest thing I found in adapting to 1.0 was finding and trying to optimize the new ascent profile. It's completely different than it was in 0.90 and before, and it's more demanding of precision. The Rapiers top out around 1400-1500 m/s in most flight profiles. This is much faster than the top speed of the Whiplash. That extra velocity can make a lot of difference. The Rapier also gives it's max thrust at higher altitude.

I play unmodded except for KER, an info-only mod.

Good luck, and happy landings!

[KerikBalm]

@KerikBalm, yes by now i already tried that and you are right. It works however you won't save any weight with the T45 over the Aerospike like chris claimed.

Also at the end you will have more fuel left with the Aerospike because of better efficiency.

Thats probably true, I haven't used it much yet because I've mostly done career since 1.0, and I haven't unlocked it yet.

Maybe I should have followed the last few parts of this thread better, I thought you were saying the turbo+lv-t45 combo didn't work, not that it was simply less efficient than an aerospike.

That design works if you swap both turbos + the lv-T45 for 3x rapiers... I don't think its as efficient, due to poor rapier closed cycle performance.

I just unlocked rapiers in career, and I've been disappointed at the results of taking my turbo+lv-t45 designs and making them rapier designs.

In the end, I think a combo turbo-rapier design is best

Edited May 20, 2015 by KerikBalm

[Corw]

I didn't play 1.0.2 much, but I had to try to see what the op is about. So I slapped really simple test SSTO with Rapier... and got it to 100km orbit on the first try, no fancy flying just full throttle to the orbit.

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[rtxoff]

Ahh yes you made a simple SSTO plane that can reach orbit and return without even a payload. Very useful. You sir will be awarded with this years "professional airplane design" award.

The name "no brainer SSTO" is fully justified i guess.

[KerikBalm]

Ok, well, I direct you to this post:

http://forum.kerbalspaceprogram.com/threads/116729-Stock-Payload-Fraction-Challenge-1-0-2-Edition?p=1896106&viewfull=1#post1896106

[Lord Aurelius]

I've had trouble with SSTO planes in 1.0.2 as well. I was never particularly good at them before (I built a few, but the longer time to orbit and my lack of piloting skills meant they were more of a novelty instead of a practical part of my game), but the engine overhaul has completely changed the ascent path and increased the flying difficulty. Engines stop working at a much lower altitude than before (airhogging doesn't work anymore which is probably a good thing) so I usually end up going up too fast and the air cuts out before I get enough speed out of them so I run out of oxidizer on the way to orbit.

It sounds like the ideal approach now is to fly up to about 13km with rapiers and then dive to build up some speed before blasting out of the atmosphere.

[Corw]

Ahh yes you made a simple SSTO plane that can reach orbit and return without even a payload. Very useful. You sir will be awarded with this years "professional airplane design" award.

The name "no brainer SSTO" is fully justified i guess.

Your original claim was that Rapier can't work for a SSTO. Made a Rapier SSTO without trying. Problem? And I guess it can move one Kerbal to orbit, so not totally useless

I don't have any experience with cargo hauler SSTO, too time consuming for my taste.

[rtxoff]

Your original claim was that Rapier can't work for a SSTO. Made a Rapier SSTO without trying. Problem? And I guess it can move one Kerbal to orbit, so not totally useless

I don't have any experience with cargo hauler SSTO, too time consuming for my taste.

No, i never claimed such a thing. I claimed that for my SSTO planes an turbojet + aerospike combination works much better. However the people here in the forum showed me planes where Rapiers work better.

I guess finally it depends on many factors what will work better. However i still wish for slightly more powerful Rapiers, they are unlocked very late in the career and they have the right to be more powerful then anything else.

[GoSlash27]

No, i never claimed such a thing. I claimed that for my SSTO planes an turbojet + aerospike combination works much better. However the people here in the forum showed me planes where Rapiers work better.

I guess finally it depends on many factors what will work better. However i still wish for slightly more powerful Rapiers, they are unlocked very late in the career and they have the right to be more powerful then anything else.

gpisic,

Actually, which approach works better is an objective fact so long as both are utilized to their full potential. The fact that turbojets and aerospikes work better in your designs tells me that there's something about your designs or profile that's interfering with your ability to utilize the RAPIER to it's full potential.

What kind of payload fractions are you achieving?

Best,

-Slashy

[luizopiloto]

Rapiers works... just needs more of them...

[Corw]

I didn't play 1.0.2 much, but I had to try to see what the op is about. So I slapped really simple test SSTO with Rapier... and got it to 100km orbit on the first try, no fancy flying just full throttle to the orbit.

*iamges*

No, i never claimed such a thing. I claimed that for my SSTO planes an turbojet + aerospike combination works much better. However the people here in the forum showed me planes where Rapiers work better.

I guess finally it depends on many factors what will work better. However i still wish for slightly more powerful Rapiers, they are unlocked very late in the career and they have the right to be more powerful then anything else.

Actually, you did said they just that: Rapiers can't get you to space.

Idk maybe it's bugged for me but the Rapier wont get me to space. As i wrote a combination of 2 Turbo jets + 1 Aerospike make a nice SSTO for me with even some payload capabilities. As soon i try to make a SSTO with only Rapiers i won't even reach 1000 m/s @ 15000m . Speed stays under 400m/s. The datasheet says they only a bit weaker then turbojets in air mode but i think they completely useless.

You didn't mention anything about payload, just that you can't make orbit with them. Try to be more clear in your statements or you come across as whiny

[rtxoff]

Actually, you did said they just that: Rapiers can't get you to space.

You didn't mention anything about payload, just that you can't make orbit with them. Try to be more clear in your statements or you come across as whiny

Read it again, i very well mentioned payload capabilities. It's just that people nowadays can't or won't read. But it doesn't matter people managed to make SSTOs with Rapier engines with over 30% payload fraction so i will shut up now.

I guess i am a lousy pilot :/

Edited May 21, 2015 by gpisic

[Wanderfound]

Read it again, i very well mentioned payload capabilities. It's just that people nowadays can't or won't read. But it doesn't matter people managed to make SSTOs with Rapier engines with over 30% payload fraction so i will shut up now.

I guess i am a lousy pilot :/

In need of practice, perhaps.

It's basically just "climb until the air thins, level off to break the sound barrier, then climb as slowly as your heating limits allow until rocket time". And in stock or FAR, you don't need a huge amount of engine:

[Chris_2]

Great words but obviously you didn't even try to make an SSTO plane with an LV-Txx and 2 turbojets. I would really love to see your airplane in action on 1.0.2 with such an configuration. Of course if you cheat everything is possible.

Really? Are you accusing me of cheating?

@KerikBalm, yes by now i already tried that and you are right. It works however you won't save any weight with the T45 over the Aerospike like chris claimed.

Also at the end you will have more fuel left with the Aerospike because of better efficiency.

It's very simple. Just look at these charts. http://imgur.com/a/N1xNb#10 Assuming you need 1400m/s (from 1200m/s on air-breathing until 2300m/s orbital speed, with some drag-losses), starting with a T/W of 1.0, then I'm not seeing the aerospike there... Actually, the aerospike is nowhere on these charts. Not even if you look at atmospheric charts. They only excel (somewhat) in the combination of atmospheric + vacuum flight. But since you use air-breathing engines for the atmospheric part you're not using them that way. My statement stays.

http://forum.kerbalspaceprogram.com/threads/121565-Optimal-engine-charts-for-1-0-2

It's basically just "climb until the air thins, level off to break the sound barrier, then climb as slowly as your heating limits allow until rocket time".

One more tip: Also during rocket time, keep your pitch down. Maybe up to 20° to get somewhat quickly through the part from 20 until 35km, but drag losses after that are really negligible so you can basically burn 'on the horizon'. And then, look at the time until apoapsis, and keep that ~1 minute in front of you, regulating with the thrust. This will result in a long (but very efficient) low-power burn until apoapsis is at 70km, requiring barely any circularisation after that.

Edited May 21, 2015 by Chris_2

[JoCRaM]

page 10: http://www.reactionengines.co.uk/tech_docs/JBIS_v56_108-117.pdf

The thrust on a SABRE is low at mach 1, so the ascent profile needs to take that into account.

Edited May 21, 2015 by JoCRaM

[Levelord]

In need of practice, perhaps.

It's basically just "climb until the air thins, level off to break the sound barrier, then climb as slowly as your heating limits allow until rocket time". And in stock or FAR, you don't need a huge amount of engine:

http://i.imgur.com/jThxkKK.jpg

So basically you're saying "there's nothing wrong with the RAPIERs as long as you install a mod that makes them useful again". Which has nothing to do with gpisic's ascent profile or piloting.

[rtxoff]

Really? Are you accusing me of cheating?

It's very simple. Just look at these charts. http://imgur.com/a/N1xNb#10 Assuming you need 1400m/s (from 1200m/s on air-breathing until 2300m/s orbital speed, with some drag-losses), starting with a T/W of 1.0, then I'm not seeing the aerospike there... Actually, the aerospike is nowhere on these charts. Not even if you look at atmospheric charts. They only excel (somewhat) in the combination of atmospheric + vacuum flight. But since you use air-breathing engines for the atmospheric part you're not using them that way. My statement stays.

http://forum.kerbalspaceprogram.com/threads/121565-Optimal-engine-charts-for-1-0-2

One more tip: Also during rocket time, keep your pitch down. Maybe up to 20° to get somewhat quickly through the part from 20 until 35km, but drag losses after that are really negligible so you can basically burn 'on the horizon'. And then, look at the time until apoapsis, and keep that ~1 minute in front of you, regulating with the thrust. This will result in a long (but very efficient) low-power burn until apoapsis is at 70km, requiring barely any circularisation after that.

I am not sure what is this all about you want to tell us here. You are sucking some numbers out of your fingers like T/W ratio 1.0 which might or might not be the case for my plane. Also you pretend to know exactly how i fly my plane (firing the aerospike in vacuum) while i might do something else (supporting the turbojets with the spike while still in the atmosphere). And also to make your claims look more believable you are linking to some charts which are the great work of another guy but do not fit at all in my case.

Well done, you just punched into my face with your ingenuity.