Sign in to follow this  
rtxoff

Rapier in 1.0.2 completely useless

Recommended Posts

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 :D

Quite. That's called a "Laythe lander", and they're rather useful.

Share this post


Link to post
Share on other sites

Getting to orbit is achieved quite easily using the R.A.P.I.E.R - and also air hogging is no longer neccessary anymore. Putting an engine pre-cooler in your design will give the R.A.P.I.E.R an extra punch bevor it flames out.

Fying SSTOs in 1.0.2 is no longer a pain as it was in previous versions of KSP for me. The only thing is, that my current designs have to be bigger than the previous ones to reach orbit, but i guess, this will equalize when going deeper into the new aero simulation.

Share this post


Link to post
Share on other sites
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.

In which universe did I say anything like that? To quote: "in stock or FAR, you don't need a huge amount of engine".

Single-engine stock SSTO:

8uF0mRw.jpg

Edited by Wanderfound

Share this post


Link to post
Share on other sites

Three tips unrelated to engines and TWR that might help:

1) Try to get the spaceplane balanced as much as possible in regard to where the CoM and CoL is. This of course is a basic principle to experienced spaceplane builders in KSP, but with the new aero it is even more important. Whenever you deflect your control surfaces, it creates drag, just as they do if used as speed brakes. If your spaceplane is properly balanced and doesn't have a heavy nose, the control surfaces won't be "dragging" the tail the whole flight just trying to keep the nose up.

2) Proper fuel tank placement helps as well. As you burn fuel, the CoM will obviously shift, so you don't want all of your fuel in the front or all in the back, or your control surfaces will have to work that much harder to maintain attitude (reference previous tip). Similar thing with payload bays. The larger the payload, the more of an impact it will have on the CoM after you jettison it (or if you test fly your spaceplane empty and get it tweaked just right, and then you throw a payload in it and it throws off the CoM/CoL balance).

3) Going back to the first point again, use gentle control inputs. If your doing the dive down and pull up method, be careful on how aggressively you pull up, the combined drag from control surface deflection and the increase in Angle-of-Attack as you pull the nose up will cause a huge increase in drag. You may punch through the Mach and start accelerating rapidly, only to have your airspeed slapped back to subsonic on an aggressive pitch back. Bring up the aero-forces overlay and watch the drag indicators grow and shrink as you maneuver the spaceplane around. If you don't have a joystick, you can use trim to get the same gentle effect (Alt-W,A,S,D,Q,E for trimming and Alt-X to reset).

Hope this helps some people. :)

Edited by Raptor9

Share this post


Link to post
Share on other sites

Rapier, the most OP method to run SSTOs is "completely useless"?

What an uninformed tread is that?!

Share this post


Link to post
Share on other sites
Rapier, the most OP method to run SSTOs is "completely useless"?

What an uninformed tread is that?!

RAPIERs aren't OP either. Once they get you into orbit, they pretty much can't get you anywhere else without re-fueling.

If you think RAPIERs are OP for simply getting you into orbit, then I don't think you quite understand the point of having RAPIERs (or SABRE engines) in the first place. They are designed to be used in SSTOs, the same applies in real life with the Skylon.

Share this post


Link to post
Share on other sites

Yea... "IN STOCK OR".... being the key part...

But, to address a different post... going back to the post about the optimal engine chart, and the lack of an aerospike showing up...

The LV-T45 doesn't show up either.

The LV-909 does... but the aerospike has the same TWR, and 5 less vacuum Isp. Its not hard to imagine that it beats the LV-909 in every way at 20km.

We also need to consider the nodes and node sizes, not just the mass, TWR, and Isp of those charts.

A poodle make show up as the optimum engine... good luck fitting that on a mk2 spaceplane with 2 Turbos.

Implicitely, only 1.25m diameter engines have been considered.

The LV-909 is out of contention in most cases (even if it shows up on that chart) because of its low total thrut- you need 3 free nodes to get comparable thrust, and that means more drag.

So it comes down to

LV-T30 vs LV-T45 vs T-1 Aerospike

Isp: 300 vs 320 vs 340 (assuming that when they are lit, they are all getting close to vacuum Isp

TWR: 17.5 vs 13.6 vs 12.2

Thrust: 215 vs 200 vs 180

The actual engine masses and TWR aren't so important, as the difference between them is only 0.25 tons, which compared to the rest of the spaceplane dry mass (turbos, wings, intakes, excess LF, etc), is pretty insignificant.

So, just look at total thrust.

LV-T30 vs 45

the 30 gets 7.5% better thrust, the 45 gets 6.7% better Isp.

People choose the 45 (although that may be due in part to gimballing)

LV-T45 vs T-1 Aerospike

the 45 gets 11.1% better thrust, the Aero gets 6.25% better Isp.

The comparison isn't so different... it could be worth it... but I suppose there's a "thrust threshold" that one doesn't want to go below (which is why the LV-909 isn't being used much- although if LV-Ns can work, I'm sure enough LV-909s could work).

Those charts you linked to do nothing to address the 45 vs aerospike question

Share this post


Link to post
Share on other sites
Putting an engine pre-cooler in your design will give the R.A.P.I.E.R an extra punch bevor it flames out.

How exactly do those work? What do they do, and does it matter where they're placed?

Is the Engine Nacelle the exact same thing with a different look?

Share this post


Link to post
Share on other sites
How exactly do those work? What do they do, and does it matter where they're placed?

Is the Engine Nacelle the exact same thing with a different look?

The intercooler is similar to the nacelle in that it has a bit of LF and a bit of intake, but it's also a very good heat sink (the nacelle might be too, I haven't checked). The nacelles now have a radial attachment pylon included as well.

Share this post


Link to post
Share on other sites
Yea... "IN STOCK OR".... being the key part...

But, to address a different post... going back to the post about the optimal engine chart, and the lack of an aerospike showing up...

The LV-T45 doesn't show up either.

The LV-909 does... but the aerospike has the same TWR, and 5 less vacuum Isp. Its not hard to imagine that it beats the LV-909 in every way at 20km.

We also need to consider the nodes and node sizes, not just the mass, TWR, and Isp of those charts.

A poodle make show up as the optimum engine... good luck fitting that on a mk2 spaceplane with 2 Turbos.

Implicitely, only 1.25m diameter engines have been considered.

The LV-909 is out of contention in most cases (even if it shows up on that chart) because of its low total thrut- you need 3 free nodes to get comparable thrust, and that means more drag.

So it comes down to

LV-T30 vs LV-T45 vs T-1 Aerospike

Isp: 300 vs 320 vs 340 (assuming that when they are lit, they are all getting close to vacuum Isp

TWR: 17.5 vs 13.6 vs 12.2

Thrust: 215 vs 200 vs 180

The actual engine masses and TWR aren't so important, as the difference between them is only 0.25 tons, which compared to the rest of the spaceplane dry mass (turbos, wings, intakes, excess LF, etc), is pretty insignificant.

So, just look at total thrust.

LV-T30 vs 45

the 30 gets 7.5% better thrust, the 45 gets 6.7% better Isp.

People choose the 45 (although that may be due in part to gimballing)

LV-T45 vs T-1 Aerospike

the 45 gets 11.1% better thrust, the Aero gets 6.25% better Isp.

The comparison isn't so different... it could be worth it... but I suppose there's a "thrust threshold" that one doesn't want to go below (which is why the LV-909 isn't being used much- although if LV-Ns can work, I'm sure enough LV-909s could work).

Those charts you linked to do nothing to address the 45 vs aerospike question

Also another thing not mentioned yet is the compact design of the aerospike. It is also much more esthetic on a plane then the LV-T45.

Share this post


Link to post
Share on other sites
RAPIERs aren't OP either. Once they get you into orbit, they pretty much can't get you anywhere else without re-fueling.

If you think RAPIERs are OP for simply getting you into orbit, then I don't think you quite understand the point of having RAPIERs (or SABRE engines) in the first place. They are designed to be used in SSTOs, the same applies in real life with the Skylon.

Personally, I think RAPIERs and turbos are still both a bit OP. It really shouldn't be practical to use them in vertical-lift SSTO designs.

Best,

-Slashy

Share this post


Link to post
Share on other sites
Personally, I think RAPIERs and turbos are still both a bit OP. It really shouldn't be practical to use them in vertical-lift SSTO designs.

Best,

-Slashy

Tend to agree with this, they really shouldn't be the most efficient vertical lifters.

Although as many are attached to cargo carrying ssto planes I can't imagine them getting much of a nerf.

Share this post


Link to post
Share on other sites
The intercooler is similar to the nacelle in that it has a bit of LF and a bit of intake, but it's also a very good heat sink (the nacelle might be too, I haven't checked). The nacelles now have a radial attachment pylon included as well.

As far as I can tell, the "precooler" is just another type of fuselage fuel tank with a built-in air intake. Its intake is just bigger than the other ones and, more importantly, STRAIGHT SIDES instead of being bulged out so it's easier to attach radially. I don't think it actually affects the temperature of the IntakeAir, and I don't think that's even considered by the game. I think they just called it a "precooler" to encourage players who'd never seen this part before 1.x to use it on SSTOs, because the old fuselage intakes have long carried a stigma of being useless. In any case, the minor amount of air-hogging provided by the "precooler" is actually a good thing. I find it keeps RAPIERS running longer and stronger than just using ram intakes, and has lower drag for the amount of extra IntakeAir than any of the radial intakes.

With the RAPIER, it seems that the real question is whether they will run out of IntakeAir at 20km and thus flame-out asymmetrically, or just die naturally at 25km from a symmetrical inability to produce thrust. 2 RAPIERS + 2 ram intakes, usually the former happens. 2 RAPIERS + 2 ram intakes + 2 precoolers, usually the latter happens.

Say what you will about the RAPIER in 1.x, at least these days you don't have to worry about the order in which you add engines and intakes so as to avoid asymmetrical flameout. If you've got enough intakes, you run out of thrust before you run out of air :)

Share this post


Link to post
Share on other sites

Does part clipping in any way affect the drag ?

Im a bit confused with the new drag model and the way FAR calculates it. I want to stay stock but i am missing some pieces:

- The angle of attack matters, but is air really calculated as a stream ?

- what about part clipping ?

- someone mentioned that its all about parts, so 4 FLT100 are worse than 1 FLT400 ?

Share this post


Link to post
Share on other sites

Recently, I've been seeing if I can create a SSTA (Single Stage To Anywhere) using 4xRapier and 2xWhiplash.

http://imgur.com/8yBVSQu

For an SSTO plane encumbered with all the resource harvesting equipment, I can get this thing to a good 200Km orbit, but I need more ideas to get it landed and mining on Minimus.

Share this post


Link to post
Share on other sites

@Dave, that is a cool looking SSTO. How does your flight profile look? I count 7 ram air intakes and 4 structural intakes (Can't see the bottom), and 6 engines. Does going down to 6 intakes hurt the dV? Seems like too much intake air, but then again I haven't unlocked rapiers yet in my career game. :)

Share this post


Link to post
Share on other sites

There's actually 6 structural intakes, and not much else underneath except two small ore tanks.

The turbo-jets and rapiers are toggled with different hotkeys, as is the mode switch. I take off with just the jets, just to clear the ground under control, then flip on the rapiers and climb at 45degrees. I flip back and forth between tracking and the following the velocity-vector so the pitch slowly declines and I accelerate to around 1,000m/s as the atmosphere gets thin.

When the air is thin enough that the rapiers get lower thrust than in closed-cycle mode, I flip them over and have some extra air to keep the turbo-jets going a bit longer.

Above 40ish Km, I just keep it aiming down the velocity-vector and get a long shallow climb to orbit.

The best I've done is around 800 fuel and 1000 oxygen left in a 90Km orbit, so I can raise it a bit, but its not going far!

Share this post


Link to post
Share on other sites
There's actually 6 structural intakes, and not much else underneath except two small ore tanks.

The turbo-jets and rapiers are toggled with different hotkeys, as is the mode switch. I take off with just the jets, just to clear the ground under control, then flip on the rapiers and climb at 45degrees. I flip back and forth between tracking and the following the velocity-vector so the pitch slowly declines and I accelerate to around 1,000m/s as the atmosphere gets thin.

When the air is thin enough that the rapiers get lower thrust than in closed-cycle mode, I flip them over and have some extra air to keep the turbo-jets going a bit longer.

Above 40ish Km, I just keep it aiming down the velocity-vector and get a long shallow climb to orbit.

The best I've done is around 800 fuel and 1000 oxygen left in a 90Km orbit, so I can raise it a bit, but its not going far!

Hide the radial tanks in a service bay. They add full drag even when they look like they are shielded. Do you launch with empty ore tanks? Maybe you could get some up with you and convert it in LKO. Saves the empty weight of additional tanks if nothing else.

Share this post


Link to post
Share on other sites
Im a bit confused with the new drag model and the way FAR calculates it. I want to stay stock but i am missing some pieces:

- The angle of attack matters, but is air really calculated as a stream ?

Never used FAR, but I'm fairly certain in stock the air is calculated as a stream. Case in point: first plane I built in the new aero was an aircraft with a similar layout to the F-86. Single cylinder-shaped fuselage with low-mounted swept-wings, and the horizontal tail plane was mounted high over the engine nozzle at the base of the vertical tail fin. Whenever I would pitch up, the nose would want to tuck upwards even more, and it was hard to push out of a positive pitch maneuver. Couldn't figure out why it was doing this in the pitch up maneuver cuz the CoM and CoL were set properly, the fuel burn wasn't affecting the CoM, and it was extremely stable, almost flew itself straight and level.

After looking at it from the side, I suspected that when the plane started to pitch up, the airflow to the horizontal tail surfaces was getting blocked by the wings when it got to about 10-15 degrees AoA. I used the offset tool to move the horizontal tail about 1/3 up the length of the vertical tail fin, and it flew just fine. No nose tuck, no issues pushing out of the positive pitch. I couldn't come up with any other reason than that, so I suspect that the air, as a stream, wasn't reaching the tail after being blocked by the wings. After I moved the tail plane to keep it in the airstream in all maneuvers, no issues.

Edited by Raptor9

Share this post


Link to post
Share on other sites
- The angle of attack matters, but is air really calculated as a stream ?

- what about part clipping ?

- someone mentioned that its all about parts, so 4 FLT100 are worse than 1 FLT400 ?

1. Not a stream as such, the attitude vs the surface prograde vector determines angle of attack.

2. Part clipping has no effect on aero; parts that are clipped are treated as if they were in their original locations, e.g. that plane I linked earlier with the clipped intakes still experiences the full drag of those intakes.

3. 4 FLT100 are equivalent dragwise in all directions to 1 FLT400, assuming the 4 FLT100s are in a single stack.

FAR is completely different, it creates a single 3d shape based on the completed craft and runs aero calcs on that, so clipping very much matters. FAR also handles parts being blocked by other parts in the airstream, as I understand it.

Share this post


Link to post
Share on other sites

Let me just post these here. :cool:

A217E53E20B73A9B3A6D298D3DD9CA5324959507

EEC452EC3ED364329188185E73A4E295B3278ED7

So yeah, I've managed to put a Mk2 SSTO plane using two turbojet engines and one R.A.P.I.E.R. engine and it delivered a tiny satellite and there was fuel left for reentry and some atmospheric flight.

Deadly Reentry was too harsh so the plane broke up on the return home, but Valentina and Jebediah survived when their cockpit parachuted down into the ocean.

This is my second SSTO, the first being made hours before. I've never tried to sit down and make such a vessel. So if I made it, anyone can. ;)

Edited by lajoswinkler

Share this post


Link to post
Share on other sites
Recently, I've been seeing if I can create a SSTA (Single Stage To Anywhere) using 4xRapier and 2xWhiplash.

http://imgur.com/8yBVSQu

For an SSTO plane encumbered with all the resource harvesting equipment, I can get this thing to a good 200Km orbit, but I need more ideas to get it landed and mining on Minimus.

This is for FAR, but something similar should work in stock:

Javascript is disabled. View full album

Process the ore tank into LF and you should have enough to hit Minmus for a full refuel.

Share this post


Link to post
Share on other sites
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this