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Spaceplane Woes in the new version.


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So, for the first time since the update, I decided to play and instantly set about making a SSTO spaceplane based on a previous design.

Unfortunately physics seems to have changed- and with the new heat mechanic, it breaks. So... help? I only had one design that ever remotely worked, and without that I'm screwed on the SSTO field. Is there an updated guide? Some blueprint I can reverse engineer? Something?

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Tassyr,

My 1.02 spaceplane stuff is still in the ballpark. You will have to juggle the fuel/ oxidizer proportions a bit.

http://forum.kerbalspaceprogram.com/threads/118728-Slashy-s-1-02-Spaceplane-recipe

A lot of new advances as we're getting a handle on 1.04 aero, so apologies; I haven't done a 1.04 recipe yet.

*edit* forgot: http://forum.kerbalspaceprogram.com/threads/129374-Pro-SSTO-builder-pilot-Challenge

This is where I'm at now for 1.04. Reverse- engineering the designs submitted for this challenge (and flying the profiles correctly) will get you where you want to be.

Best,

-Slashy

Edited by GoSlash27
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Old SSTO vs New SSTO:

Similar to girlfriend vs wife- Girlfriend would do amaxzing things that would bring a smile to your eyes and a tear to your face; Wife has her own play book which includes more work and less fun.

Jokes aside, I am rather enjoying the "new" SSTO. When I have a failure, which is uh... alot, it forces to me to find the part that I am "forcing". That is, I am being lazy and not putting thought into the design. Normally the part that fails is the part that I already knew would fail but tried it anyway just to see if I could Get Away with It.

For instance, I just started playing around with Mark III parts and had a design that seemed to have too much nose and butt, without much in the middle. The numbers all added up, CoM and CoL looked good, but the fuselage sheared off during takeoff. The thing is, looking at it just before I hit "Launch", I thought to myself, "I'd never get on that, it'll fall apart on the takeoff roll." Sure enough, about 200 m off the deck, I pulled up and only half of the spaceplane listened.

I haven't had too much issue with re-entry heat, but I played a bit with the FAR/DRE combo, and that will definitely instill good habits. Best I can offer is get instruments! Whether it is KER or MechJeb or any similar mod out there, you need to keep an eye on what is going on out there. The stock GUI actually does provide the info needed, however it is not well presented. The analog dials are suitable for landing, but it is difficult to tune your descent. I shoot for around 200-250 m rate of descent and flatten it out before things get too hot. If it gets far beyond 300m, things get a bit toasty and may not make it out of the oven.

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For instance, I just started playing around with Mark III parts and had a design that seemed to have too much nose and butt, without much in the middle. The numbers all added up, CoM and CoL looked good, but the fuselage sheared off during takeoff. The thing is, looking at it just before I hit "Launch", I thought to myself, "I'd never get on that, it'll fall apart on the takeoff roll." Sure enough, about 200 m off the deck, I pulled up and only half of the spaceplane listened.

Did you do it pre-1.0.4? (even as late as 1.0.3)

One of big underappreciated changes of 1.0.4 was fixing the connection strength between MK3 parts. While back then it was very flimsy, currently it's rock solid and you need to hit the ground really hard to break it.

Okay, to the topic.

Lots of old designs don't work due to part count or non-node attachments vastly increasing the drag. Instead of rebuilding old designs, try new ones, and very simple too. I've managed a tiny SSTO plane in 14 parts, that *just* made it to the orbit, and a bit bigger in 15 parts that got to the orbit with 1500m/s left and a pilot. There's a different flight profile - the jets produce next to no thrust above 20km, but you can use them to get a pretty 1000-1100m/s in horizontal flight between 10-15km, and the air is thin enough there that you won't burn up before you start the final climb.

Seriously, at higher altitudes the aero is so forgiving that you are able to circularize at 40km - and it's a valid method of flying SSTOs! (if rather troublesome). Drag "by default" is much more forgiving than in the past, but if you're careless, it can come and bite you in the back - badly angled parts do have potential for more drag than they did.

Well, first things first: No more intake spam. You can add intakes to keep the engine running above 30km, so what if from some 23km it produces no thrust. One intake per engine is enough currently.

Shock cone has ridiculously low drag, lower than nose cones. Use it to tip all "hulls" and "nacelles" of your plane.

Occlusion from drag occurs through node connections. Things attached radially aren't occluded (with some obscure exceptions).

Don't overdo it with wing area. In the past people loved to build bricks of wing elements and call them fancy fighters. You can still build bricks of wing elements but they won't fly faster than 100m/s.

And really the best advice I can think of: Start light. Build something that can reach orbit with zero payload first, and then increase its payload ratio gradually. If you start with given payload in mind, and start adding things to increase the carrying capacity of the plane around the payload, you won't get far.

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Yep. Also, the K-Prize challenge thread shows many, many working examples.

Small tutorial (deliberately without pictures):

A simple blueprint (no payload) from back to front, in order of construction sections:

- Hull: 1 Rapier, 1 1k battery, 2 "long" adapters Mk2-1.25m, 1 short mk2 liquid fuel tank in between these two, 1 mk1 inline cockpit, 1 shock cone intake.

- Sides: 2 delta wings, 4 elevon #1 control surfaces attached to the trailing edge, 2 airbrakes mounted to the top, 2 moving winglets.

- undercarriage: three small landing gears, two below the wings, 1 slightly clipped into the hull (aim for a few degrees of nose-up pitch). Optional: 1 1x6 solar panel with "hard-casing".

- top: small delta wing + 1 elevon #1 as rudder. optional: small antenna

Tweaks: - unlock steering for front gear, set brake power for rear landing gears to 30/30

- inner elevons of main wing and front winglets: yaw: no; roll: no; pitch: yes;

- outer elevons of main wing: yaw: no; roll: yes; pitch: no

- rudder elevon: yaw: yes; roll: no; pitch: no

Action Group: #1: toggle intake

Further instructions: put the CoL slightly behind the CoM (can be relatively far behind it, but does not have to).

Rear landing gears should be only slightly behind the CoM

Flying instructions: You will probably end up with an initial TWR slightly below 1, so: Take-off, level at 200m altitude or below until you reach at least 250m/s, then slowly pitch up to a degree where you can still slowly gain speed whilst climbing. Do so until 10,000ms, level off. Gain speed until >800m/s, pull up to around 10 degrees. If parts start to overheat, pull up a bit and try to climb more quickly. Stay in air breathing mode as long as you gain speed, only switch to closed cycle when you cannot accelerate anymore (target terminal air breathing speed: >1400 m/s). Use action group #1 to switch mode by closing the intake. Pull up to ~30 degrees until apoapsis hits 72kms (for safety margin). Set SAS to "prograde" to minimize drag. Circularize as usual (prograde burn via SAS can be helpful).

checklist prior to deorbiting:open intake, manually switch mode for rapier to air breathing. Transfer any fuel and oxidiser to the tank in the front. You can already click the brake button to deploy the airbrakes. retract solar panels, if extended. de-orbit by aiming for a periapsis of ~10,000m around 30 degrees behindKSC.

Land safely ;) .

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Did you do it pre-1.0.4? (even as late as 1.0.3)

One of big underappreciated changes of 1.0.4 was fixing the connection strength between MK3 parts. While back then it was very flimsy, currently it's rock solid and you need to hit the ground really hard to break it.

I am on 1.0.4. I distinctly recall the F3 log indicating the first failure was between MkIII Passenger and MkIII Rocket fuel fuselage. This did occur at hypersonic speeds deep in the thick (~200 m) though, which might have had something to do with the failure. :rolleyes:

Plane had control issues (could barely get the nose up) and I enabled RCS to change AoA while moving somewhere between 300 and 400 m/s. When it raised nose about 10-15*, the craft came undone. It was as much pilot error as mechanical failure.

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So, for the first time since the update, I decided to play and instantly set about making a SSTO spaceplane

Owch.

So you feel it normal to start off a exercise program by running a competitive marathon?

Because SSTO is a rather high achievement, that one should only really try when you understand the tools, rules and capabilities of your systems.

Familiarise yourself with the new physics rules, and the new partsets, before going nuts on such a challenging act as building a SSTO.

.... failure ... This did occur at hypersonic speeds deep in the thick (~200 m) though, which might have had something to do with the failure. :rolleyes:

Plane had control issues (could barely get the nose up) and I enabled RCS to change AoA while moving somewhere between 300 and 400 m/s. When it raised nose about 10-15*, the craft came undone. It was as much pilot error as mechanical failure.

15 Degree angle-of-attack, at sea level, at hypersonic speed?

Ok, so you are basically ramming into a granite cliff, and wonder why your paintjob is getting scratched?

Based on this meagre info, I'd say:

1) You have too little wing, and too much engine.

2) The "too little wing" above may actually be too little control authority?

3) You need to ascend to a decent working altitude at subsonic speeds, before hammering the throttle.

Edited by MarvinKitFox
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Owch.

So you feel it normal to start off a exercise program by running a competitive marathon?

Because SSTO is a rather high achievement, that one should only really try when you understand the tools, rules and capabilities of your systems.

Familiarise yourself with the new physics rules, and the new partsets, before going nuts on such a challenging act as building a SSTO.

15 Degree angle-of-attack, at sea level, at hypersonic speed?

Ok, so you are basically ramming into a granite cliff, and wonder why your paintjob is getting scratched?

Based on this meagre info, I'd say:

1) You have too little wing, and too much engine.

2) The "too little wing" above may actually be too little control authority?

3) You need to ascend to a decent working altitude at subsonic speeds, before hammering the throttle.

Hey, it's not starting with a marathon. Previous to this update I had a -very- efficient design and was very good at getting it to orbit. :mad:

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Hey, it's not starting with a marathon. Previous to this update I had a -very- efficient design and was very good at getting it to orbit. :mad:

It's like going from running marathons straight into competing in the Tour de France. Some of the old bits will still work (heart/lungs) but a lot is different.

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It's like going from running marathons straight into competing in the Tour de France. Some of the old bits will still work (heart/lungs) but a lot is different.

And now I know that. But I didn't know how much had changed or how badly it would impact my launches.

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It's like going from running marathons straight into competing in the Tour de France. Some of the old bits will still work (heart/lungs) but a lot is different.

Especially since the Tour de France is done on a bicycle, while marathons are on your feet.

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Hey, it's not starting with a marathon. Previous to this update I had a -very- efficient design and was very good at getting it to orbit. :mad:

It may look the same, but Aerodynamically, it is quite different. Exact part specs have changed, too.

Even a rough-and-tumble rocket design feels this, and designs have had to be tweaked a bit.

A fine-balanced low-margins enterprise such as a SSTO spaceplane will need significant redesign.

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The good news is that nowadays you start by building something that looks like a 'plane.

Then make it go Mach 5+ on jets between 15km-20km altitude, point at the sky and 'light the blue touch paper'.

My old designs, based on intake-spam and flying to the edge of the atmosphere on jets don't even vaugely work, but simple spaceplaces seem easier to make now.

The worst thing about them is how many people can't say "spaceplane".

Incidentally - these are 5 single-rapier SSTO designs available on dropbox that I have put together to illustrate the evolution of a spaceplane. The first two are vertical-launch, closed-cycle and airbreathing, then there are two drone planes being the smallest I could make and an easier one to fly ^^. The last is a 'proper' spaceplane, with enough dV left in orbit for rendezvous, docking and de-orbit plus around 5km/s dV once back in airbreathing mode. I've put these together for part of a tutorial that I will be writing and would appreciate comments.

Edited by Pecan
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All my old designs worked "out of the box" with 1.0.2+ stock atmo, but that's because all my old designs were for old FAR.

That said, if you want something that flies a bit like a pre-1.0 spaceplane check out some of the engines from OPT. The jets will still flame out around 25km, but you'll be going 1800m/s on a small/medium SSTO, so that's not a huge concern. Not exploding due to overheating is more important.

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