Can someone try and get this large SSTO into orbit? I got to 44km after 6 hours str8 of creating

[fireblade274]

I've previously built my first SSTO not too long ago, and earlier today I decided to take a break from trying to move a Class E asteroid to making a Large Transport Plane that could move large cargo into an orbit of at least 70k, and return, thereby being efficient, and fun. To simulate the max payload the largest cargo cargo container, I've used a fully loaded jumbo fuel tank.

Pic of craft

https://www.dropbox.com/s/k051xv20warfyn8/2015-08-15_00001.jpg?dl=0

How far I've gotten

https://www.dropbox.com/s/zw4v7dn72stq1t0/2015-08-15_00002.jpg?dl=0

Craft file

https://www.dropbox.com/s/a2jc7gwvwqmqyzp/LTP.craft?dl=0

If anyone can get this to at least a 70km stable orbit, and bring it back down with enough fuel to make a final approach to the runway, I'll be one happy camper. As long as you don't touch or use fuel from the Jumbo tank in the cargo bay, and I would like to see the basic design stay the same, such as the wings, and ejected fuel along the bottom; do what ever you can or even just give me a few written tips here that I can implement myself.

How I got to 44k As-Is:

Take off (right click on large ailerons just before end of runway and activate them for good handling/takeoff) point to the 25degree angle on navball

Chill till you reach about 20k. Once you start losing orbital velocity, or when you want to, right click on outermost under-slung fuel tank and open up liquid fuel to them on both sides

Press R for RCS

Press spacebar to activate "Reliant" engines

Let jets run as much as you like until flame out. Press space to ditch jets on the wings; press Abort to toggle (off) all jets left (those not on the wings)

Right click on innermost under-slung fuel tanks and open up liquid fuel to them on both sides. Right click on 4x rocket fuel tanks connected to "Reliant" engines and open up liquid fuel to all 4. Open up fuel to Mk3 adapter (rear of main body)

All rocket fuel tanks should now be available to the Reliant's. Press spacebar to ditch outermost under-slung fuel tank once completely depleted; press spacebar to ditch innermost underslung fuel tank. I don't think i touched my controls then whole way up, just stayed at 25degree elevation heading, till i needed to point up more as i got closer to max orbit height.

If you get it to orbit, and you bring it down with the fuel tank, fantastic. If you want to ditch it before re-entry, remember to ditch the forward wings on the command module to stop lift from being too up front. Or maybe you will still need those; but like previous designs i think they will mess your ships balance up if you leave them on after ditching heavy cargo.

That's as far as I've gotten before I ran out of fuel and peaked at 44k. When I started making the I was using the RAPIER's and got to 35k, then after "modifications" i was getting to 26k, then I did something good I guess and I'm stuck at around 44k atm. I need to go to bed now

All advice appreciated!

Edited August 15, 2015 by fireblade274

[GoSlash27]

Fireblade,

A few pointers I can give you from looking at your picture:

#1 Less is more. Simpler designs require fewer parallel stacks, intakes, pipes, and struts (especially struts). All of this conspires to make a spaceplane that doesn't want to go to space. If it ain't workin', look for what you can eliminate instead of what you can add.

#2 Don't use more intakes than you need. They add nothing but more weight and drag.

#3 Don't use radial scoops unless you have no choice. They're incredibly draggy.

#4 the Reliant isn't an ideal spaceplane engine. You don't need high thrust to make orbit in the closed cycle portion, you need high efficiency. The LV-N, Poodle, Aerospike, and Terrier are good candidates for add-on rockets, or you can simplify and use the RAPIER in closed cycle.

A couple examples of simpler designs that have the same payload capacity:

A high-efficiency "all fuel" design

A low- tech "early spaceplane"

Good luck!

-Slashy

*edit* I think this post should really be in the questions and tutorials forum.

Edited August 15, 2015 by GoSlash27

[Starhawk]

Slashy's advice is very wise.

The only thing I would add is that flight profile matters a lot. Fairly small changes in the profile can alter the final result drastically. Whichever air-breathing engines are used, make sure you suck all the delta-v you possibly can from them - make sure they get near their top speed before you climb too high and they flame out.

Happy landings!

[Nich]

So ya this is not an SSTO first off. Your recovery value is not going to be that good because you are ditching the 6 turbojet engines

I have tweaked the design a ton while trying to stick to the original intent. I have gotten AP to 75 and almost circularized but cant quite finish it. Rhino, Terriors or Aero spikes are the way to go. Nukes might be a little heavy with this design but have the advantage of moving to an all liquid design.

LTP V2

I have to say attempting an SSTO with orange tank delivery is pretty challenging with these engines.

Edited August 15, 2015 by Nich

[sal_vager]

Moved to Gameplay Q's, as it's not really a challenge, please see the challenge guidelines if you'd like to make a challenge of this.

[Sharpy]

Alright, here we go. Craft in orbit.

What I did:

- got rid of ALL fuel pipes and all but two struts.

You don't need fuel pipes for jet engines, they route fuel similarly to RCS routing monopropellant. The remaining struts hold one end of the orange fuel tank.

- Got rid of anything droppable. It's not SSTO if it loses parts along the way, and considering their construction they contributed more drag than thrust.

- Exchanged Reliants and Whiplashes. That way Reliants are connected to the big fuel+oxygen repository of the craft, directly. No need for pipes.

- As result, replaced the LF+OX radial fuel tanks with LF fuselages. The oxidizer wouldn't help the Reliants without manual transfer.

- Reduced number of RCS. Probably a bit too much - add two vernors for up and down on the back for a full set.

- Exchanged the orange tank mount for a docking port. More stable with struts on the other end.

- Moved wheels closer to CoM to ease start

- Also, used Offset on the wheels to make the plane less tilted.

- Removed the Klaw from the bay. You don't want it there, trust me.

- Deleted the side lights. They do contribute to drag. Left the front lights, useful with docking.

Things I didn't do but should have done

- Forgot to move the canards to a permanent attachment from the draggy decouplers.

- Forgot to unlock Oxidizer in the tail part. Only unlocked it some 150m/s short of orbit.

- Didn't remove enough LF to make it balanced.

Things I didn't do because it's left for the OP

- didn't replace Reliants with something of better ISp.

- didn't add nukes.

- didn't reach the orbit with the orange tank actually full. It would require quite a bit of work more.

Edit:

Still not good. After dumping the payload CoM shifts so far behind CoL the plane can only fly backwards from then on.

Edited August 15, 2015 by Sharpy

[GoSlash27]

Building on Sharpy's earlier cleanup:

It's got a little more room in the tanks (I didn't fill it completely).

http://wikisend.com/download/191948/LTPII.craft

*Edit* I chose to go with parts that were visible in the original pic, so I skipped the RAPIERS. Had I known they were okay, I would've used them instead of the TJ hybrid layout.

Edited August 16, 2015 by GoSlash27

[fireblade274]

Wow thank you guys so much for all of your input, this is all fantastic work. Its kinda overwhelming actually You guys are awesome

When taking it (or any spaceplane design) up, barring the fact that all crafts are different and circumstances will vary, what is a good rule of thumb to follow for your flight path? Do you want to go as fast as you can horizontally before switching away from jet engines, and then burn upwards at say 40degrees to continue to gain altitude?

I also guess this means that technically i have never built a full true SSTO, since my ferry craft is not a single stage and drops tanks on its side (but it still drops them off real cool like)

Edited August 18, 2015 by fireblade274

[Nich]

It depends I know rapiers pretty well and a truly optimized craft can not fly above 4km unless it is supersonic. If you have too much lift or too much thrust it is more economical to get to 15km at 150-200 m/s then level out and accelerate. dont pull up more then 15-20 degrees (i normally do 10) as it will rob too much speed. Once you hit 1400 you only need 800 more to holman transfer up to an AP of 75km. Rapiers have a ton of kick in closed cycle mode and this is not a problem. If you are lifting out on nukes you may want to pull up more as air friction at 26 km at 2200m/s is a bit too much for nukes to overcome and poping up to 32-36km with less horizontal velocity makes it more efficient

[KerikBalm]

When taking it (or any spaceplane design) up, barring the fact that all crafts are different and circumstances will vary, what is a good rule of thumb to follow for your flight path? Do you want to go as fast as you can horizontally before switching away from jet engines, and then burn upwards at say 40degrees to continue to gain altitude?

I don't think you ever want to burn upwards at 40 degrees.

Even before the jet TWR nerf, I didn't climb at more than 30.

At 30km, you shouldn't be pitched up more than 20 (or even 10, keep you AoA at 10 or less) to the horizon, go forward, not up.

Drag isn't so bad at 30+ km if you keep a low angle of attack, if you pitch up to 40, its very bad. You'll get your Apopasis up above 70km no problem with only a shallow climb after ~30-35km, burning nearly horizontal.

[Sharpy]

I don't think you ever want to burn upwards at 40 degrees.

Even before the jet TWR nerf, I didn't climb at more than 30.

At 30km, you shouldn't be pitched up more than 20 (or even 10, keep you AoA at 10 or less) to the horizon, go forward, not up.

Drag isn't so bad at 30+ km if you keep a low angle of attack, if you pitch up to 40, its very bad. You'll get your Apopasis up above 70km no problem with only a shallow climb after ~30-35km, burning nearly horizontal.

If your engines can keep up with it and hold over 200m/s, you're more than okay to climb 40 or even 80 degrees up to 10km from KSC. The shorter time you take the less fuel you wasted on the climb.

As for pitching, that depends on your intermediate engines. With nukes even 5 degrees may be too much at times. If you take a Rhino, just jump above the atmosphere at 45 degrees then circularize. Anything in between - angles in between.

Nevertheless, gain as much horizontal speed on jets as you can. You don't really need to switch them off, just let them sputter out - but start the rockets if you start losing speed. Even if the jets provide 0.1TWR at some 24km, that's still 0.1TWR extra on top of whatever the rockets provide. If you can get a 3% increase of thrust that's still 3% more than with jets off.

Anyway, the trajectory is always more or less flattened "S" - steep climb, horizontal speedup, orbital transfer, circularization. Depending on your TWR it may be more or less flattened; with poor TWR you'll be going very flat, with excessive TWR the initial climb and the orbital climb will be quite steep.

GoSlash: Nice work with the Skipper. I'd probably go with Mainsail, better TWR and ISP, but that's all personal preferences. My only actual criticism is aesthetics. Making awesome planes is twice as fun if you can make them look awesome.

Edited August 18, 2015 by Sharpy

[GoSlash27]

Sharpy,

Glad you like it. As a rule, I never make any concessions to aesthetics. I'm all about utility and efficiency, so my spaceplanes are about as exciting as a Maytag washer.

FWIW if I were to design an SSTO from the ground up to do this job (which I wouldn't), it wouldn't look like this design. I was trying to stay faithful to the original intent.

Best,

-Slashy