Rapier in 1.0.2 completely useless

[rtxoff]

After much experimenting i finally manage to make some decent SSTO planes. However in all my working designs one engine is missing, the Rapier.

The engine that is made for the only purpose of being useful in SSTO planes is not. My best combination so far was 2 Turbojets + 1 Aerospike.

Anyone else made that experience? I think the Rapier needs some balancing because right at the moment it is completely useless for me.

[regex]

Useless in what regard?

For me it is a fine engine and works as expected.

[rtxoff]

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.

[regex]

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.

Ah, you probably need to modify your ascent profile. The following craft needs to enter a shallow dive to 10km once it gets to 13.5km in order to build up enough speed to punch through the sound barrier. Once it gets going about 475m/s it's like a bat out of hell, though...

E: OP, it's Enhanced Navball.

Edited May 20, 2015 by regex

[NikkyD]

Rapier with 1 ram intake should give you at least 1400 m/s at a bit over 20.000m.

Ofc it depends on the rest of the plane how much you can achieve.

[Sufficient Anonymity]

Yeah, to follow on from regex on this one, they're not bugged - they are different, though that's rather to be expected, with the different aerodynamic model and a change in how jet engines work.

Due to the interaction between volume of air passing through and thrust, it's possible to get stuck at around 400m/s if you just have Rapiers. But you never just have Rapiers - you've always got gravity, and if you get stuck in a bit of a rut when accelerating, a bit of a dive then pitch up works wonders.

Like regex, I climb hard (45 degrees plus, depending on the craft) to around 10km, then level out, possibly putting in a little descent at around the 12km mark. Rut escaped, I then fly a gentle climb out, and by 20km (and >1000m/s) I'll by crossing my fingers that the wings don't fall off.

[Franklin]

the "dip ascent to break mach wall then softly climb again to escape" part of SSTOs has been a hard thing for a lot of players to grasp forever.

it's just that 1.0.x has made it so now you can't just brute your way through this detail like you could in the soup, and now players who previously just slapped more intakes/engines onto their SSTO get into space think something's broken.

"you have to go down to go up"

"no squad just nerfed <SSTO element> into the dirt, it's broken"

edit: although admittedly there seems to be drag issues with many-part wings

Edited May 20, 2015 by Franklin

[Tank Buddy]

Sorry to say, the Rapier is perfectly fine; your designs or piloting are poo :c (no hard feelings)

Given your spacecraft has a high enough TWR, it should be fine. The thrust increases with your current Mach number (basically dependent on speed and altitude). If your craft cannot reach a sufficient velocity before ascent to space, it will lack the necessary thrust. You can do two things:

1. ADD MOAR BOOSTERS

or

2. Modify your flight profile as to gain velocity (like diving as regex mentioned) before final ascent in order to maximize your thrust.

Good luck!

[Mako]

http://forum.kerbalspaceprogram.com/threads/116729-Stock-Payload-Fraction-Challenge-1-0-2-Edition

The results in this thread would appear to directly contradict your thread title.

[Levelord]

The spaceplanes I've flown so far never needed to dip down in order to gain speed. That wastes a lot of fuel and uneccesarily prolongs the flight to orbit... and also increases fuel requirements.

OP assuming you are working with Mk2 parts just slap on 3 RAPIERs with 4 supersonic intakes. Take off at a 30 degree inclination and level off to a 20 degree inclination at 10,000m. The plane will make it to 22,000m @ 1400m/s before the engines start to die off, then switch to rocket mode.

[GoSlash27]

All of my spaceplane designs use RAPIERs and they are by far more mass-efficient than any design I can come up with using turbojet/ rocket hybrids.

The ascent profile is different now...

Best,

-Slashy

Edited May 20, 2015 by GoSlash27

[regex]

The spaceplanes I've flown so far never needed to dip down in order to gain speed. That wastes a lot of fuel and uneccesarily prolongs the flight to orbit... and also increases fuel requirements.

Conversely, by using gravity to punch through the sound barrier you require less initial engine TWR which means less engines you have to carry into orbit or slightly more cargo (fuel, too), increasing the overall effeciency of the craft. By "wasting" a little fuel you end up with a lighter craft. Also, in practice a dive maneuver has rarely taken me longer than a minute or so to get back up to my dive altitude.

[Levelord]

Conversely, by using gravity to punch through the sound barrier you require less initial engine TWR which means less engines you have to carry into orbit or slightly more cargo (fuel, too), increasing the overall effeciency of the craft. By "wasting" a little fuel you end up with a lighter craft. Also, in practice a dive maneuver has rarely taken me longer than a minute or so to get back up to my dive altitude.

Not with this drag model, no. The less time you spend in it the less fuel and time you need to spend to get to orbit.

The current drag model doesnt recognize aerodynamic shapes or aerodynamically occluding objects (like placing a nosecone in front of a tank using the offset tools. It has to instead be placed using the attachment points in order for the aero to recognize it). This means a lot of crafts acquire unnecessary drag regardless of how aerodynamically sound the craft is.

Currently drag is stil based on part count regardless of clipping (except for cargo bays) so the ships with the least part count gets to orbit easier and that is solved by simply adding one additional RAPIER.

Unfortunately this is how I am seeing the majority of SSTOs being built in the space craft exchange because the excessive drag model encourages engine spam as the most fuel efficient way of getting to orbit (and I'm a minimalist by comparison with 3 engines).

[Red Iron Crown]

4 RAPIERs, 10ton payload, >20% payload fraction, <50 parts, no dipping to build speed, can deorbit and land safely:

RAPIERs work fine, I've had more trouble getting turbojet/rocket planes to work.

[regex]

The current drag model doesnt recognize aerodynamic shapes or aerodynamically occluding objects (like placing a nosecone in front of a tank using the offset tools. It has to instead be placed using the attachment points in order for the aero to recognize it). This means a lot of crafts acquire unnecessary drag regardless of how aerodynamically sound the craft is.

Currently drag is stil based on part count regardless of clipping (except for cargo bays)

This reminds me a lot of old FAR, where the drag was calculated by attach node, I do believe. Even clipped attach nodes induced drag, which is why it was worth your while to add antennas to open nodes inside the craft. The problem is a very tough one to solve; IIRC ferram4 had been trying to figure out a way around it for quite some time before he hit on the voxelization technique which, while being hetter for clipping parts, has its own problems to solve (like "what is a wing on this craft?"). KSP's pretty much total freedom causes no end of headaches in a lot of people.

I suppose that's neither here nor there, I'll trust you judgement because I don't spaceplane all that often.

[zarakon]

I had an SSTO made with 2 turbojets and 2 LV-T45s. Then when I unlocked Rapiers, I replaced those 4 engines with 2 Rapiers. First test flight was a failure because I accidentally went so fast that my intakes exploded.

[rodion_herrera]

The RAPIER is my best friend. It behaves like the SCRAMJET system in Orbiter's DeltaGlider, a spaceplane I'm very fond of.

[percyPrune]

One trick I have found with Rapiers is to watch the thrust like a hawk. If the thrust begins to decrease anywhere below about 8km alt then you end up with the lose-lose situation of plane decelerating=less ram effect=less thrust=more deceleration. If you can't dip your nose to increase speed & thrust before the low atmo drag slows you down then you are doomed to just cruise around the sky.

4 RAPIERs, 10ton payload, >20% payload fraction, <50 parts, no dipping to build speed, can deorbit and land safely:

... and 2 clipped ram intakes. Remember the F111 and think of the boundary layer!

[Chaos_Klaus]

The spaceplanes I've flown so far never needed to dip down in order to gain speed. That wastes a lot of fuel and uneccesarily prolongs the flight to orbit... and also increases fuel requirements.

Yeah ... you know that's physics. The game would be much easier without physics, and SSTOs would propably need less fuel then. Maybe Squad should just leave out all that physics nonsense all together.

Really, I don't see how you can complain about aerodynamics making your craft inefficient. Go build something that actually can efficiently fly in atmo.

The "exessive drag" argument is not valid aswell for two reasons: It's not exessive. With 1.0 most designs would breach the sound barrier just after leaving the runway. That is exessively low, I would say. 1.0.2 overcompensated a little, but it is still not too bad. Secondly: You also have increased lift and you surely wouldn't complain about that, right?

To conclude:

KSP now models the sound barrier. Deal with it.

[eddiew]

Rapiers do currently have a flat spot in their power delivery - namely they don't give you much below about mach 1.5. This is leading to a lot of players finding that their planes get stuck at about mach 0.95 and simply can't get through the transonic barrier without a power dive. An additional turbojet can act as a low range gearbox, pushing the rapiers into their power band where they'll take over and fling anything you like into orbit. Alternatively, if you have a regular rocket like an LV-T45 (still better ISP than a rapier) a few seconds of that might also do the job

Did some napkin maths from a few weeks ago to illustrate the problem (there are more factors, but it's reasonably close to what you'd see with a right-click on the engines). I don't know whether Squad consider it to be a problem or working as intended though, since you can use rapiers perfectly well in larger craft. Unfortunately two engine designs tend to really struggle in stock now.

I can however recommend nuFAR as a good option if you like small-medium SSTOs. Build them streamlined and you can easily move a 32 ton craft to orbit with just two rapier engines - stock definitely won't let you do that anymore.

Edited May 20, 2015 by eddiew

[Red Iron Crown]

... and 2 clipped ram intakes. Remember the F111 and think of the boundary layer!

Eh, I could make the exact same thing with an inline cockpit and the two intakes in the nose and have less drag, but it would be far less aesthetically pleasing. I really like the look of the shoulder intakes in that design.

I'll just add part clipping to MechJeb and HyperEdit on the list of ways in which I am a filthy cheater at KSP.

[percyPrune]

I really like the look of the shoulder intakes in that design.

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")

[Wanderfound]

RAPIER:

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No RAPIER:

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About a 300m/s advantage to the RAPIER.

[Chris_2]

Decrease your drag, increase your thrust. Thats the 'trick'... Streamlining your craft is more important than ever. Wings also add a lot of drag, reduce your wing area to the bare minimum for liftoff and you'll break the sound barrier more easily.

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...

[rtxoff]

Decrease your drag, increase your thrust. Thats the 'trick'... Streamlining your craft is more important than ever. Wings also add a lot of drag, reduce your wing area to the bare minimum for liftoff and you'll break the sound barrier more easily.

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...

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.