Slashy's 1.02 Spaceplane recipe

[GoSlash27]

This guide is subject to change as we learn more about 1.02 parts, aerodynamics, and physics.

Here's where I am at the moment...

This design will get 4 tonnes of payload to LKO and still leave fuel for maneuvering, retro burn, and air breathing flight home.

My basic rules of thumb:

* 1 RAPIER per 13 tonnes of aircraft

* 2 radial intakes per engine (or 1 ram per engine)

* 1 CL worth of wing area per 4 tonnes of spaceplane

* 650 units fuel per engine

* 550 units of oxidizer per engine

I'm having good luck with the strakes as wings. Adequate lift and low drag.

Stacking the sections in series creates a low frontal area, but it's not actually necessary. I've also had good results with the FL-TXX series tanks in parallel, like this:

I have noticed that 1.02 likes very minimal control surfaces. The control surfaces on the X-3 above are overkill and make the controls twitchy.

Best,

-Slashy

- - - Updated - - -

Basic takeoff profile:

This is subject to change as we refine our techniques...

*important*: Set an action group to manually switch the engine mode and toggle intakes. Auto switching is wasteful.

Takeoff at half throttle and gear up once climb is established.

Pitch up to maintain between150 and 200 m/sec airspeed.

Throttle to max

Pitch up to maintain between 150 and 200 m/sec airspeed.

Try to maintain 5* angle of attack through the climb, gradually reducing pitch until level at 200 m/sec at 10-12 km altitude

Accelerate at full throttle in level flight until supersonic and accelerating rapidly.

At the first sign of compression effects, pitch as necessary to maintain weak fog. Aircraft should top out at about 1 km/sec airspeed and 25 km altitude.

Switch to closed cycle and pitch as necessary to avoid overheating.

Orbital velocity should be achieved at approx. 35km altitude.

Best,

-Slashy

[Maukse]

Just tested my SSS (Single Stage Spaceplane, as writting SSTO create too many problems :-) ) in 1.02

Made it to LKO, but with 200-250 m/s left (was 400-450 in 1.0)

Roughly the same engine-to-weight ratio, but twice the wing-to-weight.

Might try with a quarter in hope to get a bit more deltaV for orbital rendez-vous on LKO + vernor LFO docking (in my mind, it's at least 200m/s)

So SSTA (single stage to anywhere) are dead and it's a good thing. Now we have SSS to LKO, and I will live with it, just need an orbital station around Kerbin, and one around Mun/Minmus, where I will plan my ISRU.

But the huge nerf of the LVN is just sooo painfull : /

Won't go off-topic as soon as I try with a 1/4 wing ratio, I'll give a feedback here.

Edited May 2, 2015 by Maukse

[GoSlash27]

Just tested my SSS (Single Stage Spaceplane, as writting SSTO create too many problems :-) ) in 1.02

Made it to LKO, but with 200-250 m/s left (was 400-450 in 1.0)

Roughly the same engine-to-weight ratio, but twice the wing-to-weight.

Might try with a quarter in hope to get a bit more deltaV for orbital rendez-vous on LKO + vernor LFO docking (in my mind, it's at least 200m.s)

So SSTA (single stage to anywhere) are dead and it's a good thing. Now we have SSS to LKO, and I will live with it, just need an orbital station around Kerbin, and one around Mun/Minmus, where I will plan my ISRU.

But the huge nerf of the LVN is just sooo painfull : /

Won't go off-topic as soon as I try with a 1/4 wing ratio, I'll give a feedback here.

Roger that!

Thanks for the assist!

Just for S&G, I'll see where 4 tonnes of fuel and oxidizer takes one of my current designs.

Best,

-Slashy

[TinfoilChef]

* 1 CL worth of wing area per 4 tonnes of spaceplane

Thanks for doing this. I've never done well with aircraft.

One possibly noob-ish question, what's a "CL"?

[Jarin]

Any chance of a non-rapier recipe? Would really like to see some guidelines for turbojet-based spaceplanes.

[NathanKell]

Tips:

1. Intakes have varying drag. Shock cones have the least (and are also heat resistant), but have less area than ramp intakes. The old 'scoop' radials have insane drag. The long radials have low drag, but not much area, so use lots.

2. Landing gear produce a fair amount of drag. Flip them so they're back first to lower it. Use the smallest gear you can (the old Small Gear Bay has much lower drag than the new gear because it's smaller).

3. There's still a bug with Mk3 cargo bays. Until there's an unofficial patch (or an official one, woo) be warned they cause a crapton of drag since they don't occlude the part attached behind them.

4. Wing area needed will vary since the Mk2 fuselage counts as a kinda-wing, so Mk1 or Mk3 planes need more wing area for decent AoA.

5. Climb to 10km, then dive to punch through the transonic, then climb again. If you have enough power to punch through the transonic on your way up then you're probably wasting mass on engines.

[EladDv]

Tips:

3. There's still a bug with Mk3 cargo bays. Until there's an unofficial patch (or an official one, woo) be warned they cause a crapton of drag since they don't occlude the part attached behind them.

then why do we even bother using those? in all honesty this is something that i cannot say is a minor bug that can go unnoticed during testing- you can see the aerodynamic forces within the bay

[GoSlash27]

Thanks for doing this. I've never done well with aircraft.

One possibly noob-ish question, what's a "CL"?

TinfoilChef,

That's the "lift coefficient" of the wing panel. Each panel has one (you have to right click to see it).

Just take the mass of your airframe, divide by 4, and slap on enough wing panels to match that number. Remember that this ratio applies to individual wing panels rather than pairs.

Best,

-Slashy

[NathanKell]

Did I say stuff in the bay was unshielded? Nope.

I'm talking about a part stack-attached behind the bay, not stuff in the bay.

[TinfoilChef]

TinfoilChef,

That's the "lift coefficient" of the wing panel. Each panel has one (you have to right click to see it).

Just take the mass of your airframe, divide by 4, and slap on enough wing panels to match that number. Remember that this ratio applies to individual wing panels rather than pairs.

Best,

-Slashy

Thanks for the explanation. Makes sense now (mostly). more importantly, having an idea what the numbers mean I can do something with them.

[Alshain]

Your controls may be twitchy because you are using a delta wing elevon setup (as opposed to aileron/elevator setup). You don't need a lot of elevator, try turning pitch on only for the inside control surfaces and roll only for the outside control surfaces. Of course the tail should be set to only yaw. Canards also have a tendency to be twitchy, at least they did with FAR, I honestly haven't tried them in stock yet. But it might be something to consider. Try using fixed canards if you only need to move the CoL forward. If you are using active ones, make sure those are pitching only. It's important to be specific. The game tries to figure out what you intend to do with control surfaces but sometimes it messes up and it starts moving yaw when you want to pitch. It has done that as far back as I can remember.

If you are setting your pitch/yaw/roll, then feel free to ignore this, just thought I'd help.

Personally I find ailerons and elevators easier to fly in the game, but they can be a little harder to build if your center of mass is far in the back.

Edited May 3, 2015 by Alshain

[GoSlash27]

Your controls may be twitchy because you are using a delta wing elevon setup (as opposed to aileron/elevator setup). You don't need a lot of elevator, try turning pitch on only for the inside control surfaces and roll only for the outside control surfaces. Of course the tail should be set to only yaw. Canards also have a tendency to be twitchy, at least they did with FAR, I honestly haven't tried them in stock yet. But it might be something to consider. Try using fixed canards if you only need to move the CoL forward. If you are using active ones, make sure those are pitching only. It's important to be specific. The game tries to figure out what you intend to do with control surfaces but sometimes it messes up and it starts moving yaw when you want to pitch. It has done that as far back as I can remember.

If you are setting your pitch/yaw/roll, then feel free to ignore this, just thought I'd help.

Personally I find ailerons and elevators easier to fly in the game, but they can be a little harder to build if your center of mass is far in the back.

Alshain,

Yeah, I do all of that, and it's good advice.

1.02 has definitely made controls more twitchy. I think it's their background stability assist overcompensating for the increased drag and lift. Reducing the control surface area (and allocating functions as you stated here) helps to reduce the erratic behavior. Also, I'm back to not using active rudders. I used them for less than a day with 1.0, but 1.02 made them touchy and I find the planes fly better without them.

Best,

-Slashy

[Maukse]

So, just tried :

-24.4 tons at take-off

-2 RAPIER engines

-3.5 lift from wings, 2.4 from the body (I counted only 50% of my tail part mkII-to-1.25, as it's "face-forward", does it generate full lift ?) for the static lift => total 5.9

-1 Elevon 1 (0.25) for roll control, and 1 Elevon 4 (0.18) for pitch control, per wing

-1 Advanced canard (0.4) for pitch, per side

-1 AV-R8 Winglet (0.5) for yaw control

-1 ram air & 1 air pre-cooler per RAPIER (pre cooler might be totaly useless, must try without it).

-2 basic solar panels, 1 XL drag chute (just in case, was the same weight as a tail, and I tought it might be more usefull) and 8 vernor engines.

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At first try, I was 450 m.s short to make it on a 75x75 LKO !

2nd try => 70x80 LKO with 200m/s deltaV left.

So, guidance for design is a good thing, but ascent profile is the key parameter for performance !!!

I managed to reach 12 000 - 13 000m heading 30-40°, then I aimed for a 5-10° angle, and let speed & thrust build up, until it became obvious that "everything is going to BBQheat soon" => aimed for 20-25°.

My next try will be without the "engine pre-cooler", I'm dubious about them (if you use them, don't forget that they have air intakes => assign them in your "toggle RAPIER mode / Toggle intakes " action group !!!

I noticed that RAPIER burns a lot of liquid fuel, the take-off to 12 000 meters part probably need to be optimized as well.

Edited May 3, 2015 by Maukse

[GoSlash27]

maukse,

Yeah, how you fly it is at least as important as how you build it, especially when you start balancing for payload fraction at the expense of extra fuel and tankage. If it's built wrong it either won't make orbit or it won't make orbit with any useful payload. Even if it's built right, it ain't makin' orbit if it's flown incorrectly.

I'm also not sold on the precooler. My (limited) testing hasn't shown it to add any top-end performance in air breathing mode at all beyond the increase in intake area.

Best,

-Slashy

[GoSlash27]

Interesting!

If you maintain 20 km altitude, the air-breathing speed can exceed 1,400 m/sec, saving you all sorts of fuel, which can then be traded off for additional payload.

This tactic runs the risk of burning up parts, so approach with caution!

Best,

-Slashy

[GoSlash27]

Not too shabby!

The wet wings are pretty clean, which allows me to go a little heavier on 2 engines, which means moar payload.

This one is 33 1/2 tonnes on the ramp and is still clean enough to punch through Mach 1 and get hypersonic.

Replacing the passenger compartments with LF&O or other payload and using either a smaller cockpit or remote guidance would push this one's payload fraction up to 20%.

[Maukse]

So 1 Elevon per wing for both roll/pitch control ?

[FlipNascar]

Another thing that's maybe worth adding is to disable the torque wheels in the SPH, and then enable them when you engage orbital systems. I've found a couple of occasions where I've ended up coasting to the AP and because it's dark I've now run out of electricity... S'pose you could add a fuel cell if you don't like solar panels. Or moar batteries.

And more importantly - you don't need reaction wheels below 30km anyways!

[GoSlash27]

This crudely assembled example demonstrates the relative ratios of parts that I've found to be most mass-efficient for Mk3 spaceplanes.

All tanks are 100% full at launch, including the wings.

I have 1 shuttle delta, one FL-T400, and 1 scoop intake per engine.

For all 6 engines, I have an additional 1,676 units of fuel and 1,946 units of oxidizer for orbital insertion and OMS burns.

This combo is adequate to deliver 25 tonnes of payload on station in LKO with reserves for orbital intercept/ rendezvous and deorbit burn.

The 6 engine example weighs 107t at launch and represents a 23% payload fraction.

Best,

-Slashy

[Geschosskopf]

Well, I finally got my 1st 1.0.2 spaceplane into orbit. GEEZ, what a struggle. Thanks to Slashy and many others for the tips.

http://steamcommunity.com/sharedfiles/filedetails/?id=441330117

I'm very sad about this huge thing now necessary to get a mere 4 Kerbals into LKO (or LLO). Used to be, you could slap together a perfectly functional spaceplane with no trouble. Turbojets and 909s could get even monstrous Mk3 things up no problem, even with Firespitter pontoons dangling below. You could actually have fun owning space. But the realism-mongers have won the day and made it a pain to even claw out a toehold in space.

[Maukse]

Ok great news here !

I got my first SSS to Minmus LO on orbit / crew transfer to orbital station today !

Mk II, 29 tons, mkIIcrew cabine + 1900 m/s left once in LKO.

More to follow this evening. As many already said, the trick is in the ascent profile.

[Maukse]

And here is a lifter based on the above-mentioned spaceplace :

5. 26.08% Tonnerre - 2.1 by Maukse (Single stage RAPIER/LV-N spaceplane)

Made mostly by following Slashy's guidance and my own trials.

[Warzouz]

Thx : Perfect recepee

Mine : 23T

2 rapier + 2 shock cones intakes

LF = 150+40+440+90 = 720 per engine

Ox = 550 per engine

Lift = 6.93 (a bit high but already hard to maneuver)

Fuel left in LKO = 115 fuel + 70Ox per engine (can't tell you dV because KER says 0m/s since 40km.

Edit : plane modified with Docking and second crew cabin Total 27T, same fuel, a bit more lift (those 2 MK2 parts)

Fuel left in LKO = 84LF + 48Ox per engine.

My ship has nearly no roll, though

Edited May 28, 2015 by Warzouz

[guitarxe]

Hm, I must be doing something really wrong here, how do I follow these rules of thumb?

I design a plane, weighs 97.3 tonnes, that's 7.4 Rapiers need, so I put 8 on my plane. That's 650 * 8 = 5,200 liquid fuel needed. I don't have enough, so I add more. Then I check my weight again, and now I am at 191 tonnes. That means I now need 14 Rapiers, not 8. So I add more Rapiers, and I need more fuel for them now, and I add more fuel and I check my weight, and now I need 16.8 rapiers instead of 14. Which will need even more fuel, which will increase weight, which will need more engines... and so on and so on, endless cycle... and this doesn't even count the additional wings with each addition of engines+fuel.

I'm obviously missing something here?

[Warzouz]

When you plane is built, the ratios should be as indicated.

Then you have to tweak a littlt to fit your need :

- better control and lift mean more wings

- better speed punchat low altitude replace one rapier by a turboJet

- tweak precise fuel amount by testing your plane (depends on dV you want in orbit)

My original design ended 12 tons heavier with bigger wings.

Edited June 10, 2015 by Warzouz