Need an SSTO Design + ascent path for LKO without Rapiers.

[jcthemc]

Hey everyone,

I'm at my wits end... i'm trying to build an SSTO That can carry 5 or 6 kerbals + some freight to LKO. I've tried Scott Manley's design but i just can't get it into orbit. Then i redesigned that a little, added an engine from a mod with a lot more thrust than the regular turbojet (the D-30F7 Turbojet, 775Kn @ Mach 3, from the B9 Aerospace pack) and replaced two Swivels with a Poodle, and i made it to a 70k orbit only to have no fuel left. If someone could help me out it'd be greatly appreciated.

This is the current design:

Edited February 16, 2016 by jcthemc

[RokRoland]

With any atmospheric engine you need a good ascent profile in order to make orbit efficiently. I find that you should be making close to or exceeding 1000m/s with ramjets (I have experience with Whiplashes, don't know about your mod engine) before the speed starts to drop. At this point you should be pointing upward somewhere in the 20 to 40 degree angle region depending on design.

In my book, if you are nowhere close to that, it is a matter of removing drag, removing weight, or adding more engine. It is not easy and after trying Rapiers, they almost feel like cheat mode as you won't necessarily need to put on more weight with dedicated non-atmospheric engines.

The airbreathing engine thrust curve takes some getting used to. How fast is your machine if you level it out and run full bore with the turbojets at around 11-12km? Give it a shot with the Whiplashes too, as they may perform differently due to the dynamic effects of speed and air thickness.

Edit: Some design considerations to minimize drag and weight would at first look to be get rid of some RCS ports, move to single central tail fin, experiment with removing one cargo section so you are not trying to bite too much at once, and see if you could somehow do without those draggy fuel ducts. Sometimes even minor modifications can help alleviate the drag and weight to get into that Whiplash sweet spot where you pick up speed really well.

Edited February 16, 2016 by RokRoland

[Ketatrypt]

here is a ship that I have been using lately. If flown right it can get to the mun with 7.5t of cargo, or can deliver a heapload of fuel + the cargo to LKO. (all stock parts.)

I use the skipper engine rather then the poodle, as it is more efficient in the wide variety of atmosphere pressures the shuttle goes thru. And it also produces more thrust. which is always nice. You can take out one of the cargo sections for a pair of the passenger section things, although it really shortens the cargo bay.

For engines, I have the 4 default ramjets, and they get me to about 1100m/s at 18.5km, which the ramjets loose thrust and I turn on the skipper (Obviously leave on the jet engines until they flame out, then close the intake ports for less drag)

 

I am not sure how to upload a part file, but if you really want it I can learn how to upload it for ya.

Edited February 16, 2016 by Ketatrypt

[GoSlash27]

jcthemc,

 This is my tech level 7 crew transport:

It uses the plain old Panther and LV-T45.

Some things that I'm doing that you may not be doing:

-Minimize drag. The tailcone/ adjustable ramp intake (radial) combo generates less drag than even the shock cone. Use wing incidence to generate lift, not the body. Use minimal control surfaces. Don't surface mount stuff that doesn't absolutely have to be surface mounted. I have minimal RCS ports and they're the linears, not quads.

-Use enough rocket for the job. It looks to me like you've got too much spaceplane for a single Poodle. Try a Skipper instead.

-Moar fuel. with your improved aerodynamics, you should be able to haul more rocket fuel for orbital ops.

Good luck!

-Slashy

 

Edited February 16, 2016 by GoSlash27

[jcthemc]

Well, after reading RokRoland and Ketatrypts posts, i did some more tweaking and testing, and i've now arrived at this: 

Current ascent profile (using Mechjeb / Smart ASS)

• Takeoff at ~150 m/s.
• Climb to 9~10km at 30 degrees, then adjust to:
• Climb to 19~20km at 12~15 degrees, when acceleration stagnates, activate rockets (2x Reliant), then adjust to:
• Climb to 30~35km at 25 degrees... when i'm at this point i'll manage to get it to a 85km apoapsis, but i'm still struggling to find the optimal pitch to get that 1m30s time-to-apoapsis sweet spot. Circulisation burn is no problem.

So i've made it to orbit, i've got some fuel/oxidizer left for adjustments, but it's not much. Next version i'll probably put on some extra flt-100 tanks. 

Now i'm struggling to get this thing reentered without it burning up, which i've miraculously managed once, only to crash into the water because i was fiddling around and set the power to the engines too low. Upon reentry my real issue is the fact that i can't keep it pitched up. I set my periapsis to about 40~45km, and the during the first part of reentry my pitch will be ok, only to slowly go down to nearly 0 degrees.

I feel like i'm close to where i want the design to be, but it'll take some more fiddling. Any suggestions are welcome.

In the meanwhile i'm going to try and replicate Slashy's design (thanks for posting, i love how different your approach is), get some kerbals up to LKO and continue with some contracts. i've done way too much SSTO testing the last few days.

Edited February 16, 2016 by jcthemc

[Ketatrypt]

18 minutes ago, jcthemc said:

Well, after reading RokRoland and Ketatrypts posts, i did some more tweaking and testing, and i've now arrived at this: 

Current ascent profile (using Mechjeb / Smart ASS)

• Takeoff at ~150 m/s.
• Climb to 9~10km at 30 degrees, then adjust to:
• Climb to 19~20km at 12~15 degrees, when acceleration stagnates, activate rockets (2x Reliant), then adjust to:
• Climb to 30~35km at 25 degrees... when i'm at this point i'll manage to get it to a 85km apoapsis, but i'm still struggling to find the optimal pitch to get that 1m30s time-to-apoapsis sweet spot. Circulisation burn is no problem.

So i've made it to orbit, i've got some fuel/oxidizer left for adjustments, but it's not much. Next version i'll probably put on some extra flt-100 tanks. 

Now i'm struggling to get this thing reentered without it burning up, which i've miraculously managed once, only to crash into the water because i was fiddling around and set the power to the engines too low. Upon reentry my real issue is the fact that i can't keep it pitched up. I set my periapsis to about 40~45km, and the during the first part of reentry my pitch will be ok, only to slowly go down to nearly 0 degrees.

I feel like i'm close to where i want the design to be, but it'll take some more fiddling. Any suggestions are welcome.

In the meanwhile i'm going to try and replicate Slashy's design (thanks for posting, i love how different your approach is), get some kerbals up to LKO and continue with some contracts. i've done way too much SSTO testing the last few days.

heh yea sstos require much more testing then rockets do. it can be quite addicting

Congrats to getting to space

 

As for re-entry, have you tried moving fuel around as you are decending? If your nose is heavy, try moving some fuel to the rear tanks. It can act as ballast, and will move your CoM quite effectively.  But everything else sounds about right..

you could also add better canards (and move them further forward for more leverage) which could give you more power to pull up the nose.

And one last thing, you can use shock cone intakes for more air/less drag. (Unless you like the look of those intakes) And I am not sure if the nose cones are better then the shock cone intakes. The shock cone is retarded light, and has very little drag. On my own shuttle I found that quad intakes is better then 2 intakes + 2 nosecones. The extra air is unnecessary, but they have so little weight/drag that they seem better then regular (and advanced) nosecones.

Edited February 16, 2016 by Ketatrypt

[jcthemc]

3 hours ago, GoSlash27 said:

jcthemc,

 This is my tech level 7 crew transport:

It uses the plain old Panther and LV-T45.

Some things that I'm doing that you may not be doing:

-Minimize drag. The tailcone/ adjustable ramp intake (radial) combo generates less drag than even the shock cone. Use wing incidence to generate lift, not the body. Use minimal control surfaces. Don't surface mount stuff that doesn't absolutely have to be surface mounted. I have minimal RCS ports and they're the linears, not quads.

-Use enough rocket for the job. It looks to me like you've got too much spaceplane for a single Poodle. Try a Skipper instead.

-Moar fuel. with your improved aerodynamics, you should be able to haul more rocket fuel for orbital ops.

Good luck!

-Slashy

 

Well, i've tried this design, and i can't get anywhere near orbit using the ascent profile i posted before. How are you flying this thing?

Thanks for the advise on the design changes, i'll incorporate them into mine.

EDIT: Well, i got it into orbit, only to run out of fuel on the circularisation burn. Please tell me what your ascent profile for this thing is.

 

1 hour ago, Ketatrypt said:

heh yea sstos require much more testing then rockets do. it can be quite addicting

Congrats to getting to space

 

As for re-entry, have you tried moving fuel around as you are decending? If your nose is heavy, try moving some fuel to the rear tanks. It can act as ballast, and will move your CoM quite effectively.  But everything else sounds about right..

you could also add better canards (and move them further forward for more leverage) which could give you more power to pull up the nose.

And one last thing, you can use shock cone intakes for more air/less drag. (Unless you like the look of those intakes) And I am not sure if the nose cones are better then the shock cone intakes. The shock cone is retarded light, and has very little drag. On my own shuttle I found that quad intakes is better then 2 intakes + 2 nosecones. The extra air is unnecessary, but they have so little weight/drag that they seem better then regular (and advanced) nosecones.

Will try the other canards and intakes, see how that goes.

Edited February 16, 2016 by jcthemc

[GoSlash27]

57 minutes ago, jcthemc said:

Well, i've tried this design, and i can't get anywhere near orbit using the ascent profile i posted before. How are you flying this thing?

Thanks for the advise on the design changes, i'll incorporate them into mine.

EDIT: Well, i got it into orbit, only to run out of fuel on the circularisation burn. Please tell me what your ascent profile for this thing is.

jcthemc,

 I'll kick you a copy of mine this evening.

 My profile for the "Seven":

-Launch and climbout in (dry) mode at 5° pitch

-Transition to afterburner at approx. 220 m/sec. 

-Maintain 5° pitch to 10km altitude and 820 m/sec airspeed.

-Engage closed cycle and slowly raise pitch to 15°.

-Maintain 15° pitch until apoapsis exceeds 45km.

-Follow prograde and throttle as necessary to achieve orbital apoapsis and circularize.

You should end up in orbit with around a tonne of LF&O, good for a couple hundred m/sec DV.

Best,
-Slashy

 

[Ketatrypt]

yea pretty much what slashy said...

 

generally with the whiplashes, I go to 8km subsonic, then speed up while still climbing, and when I get to 12km, I level out, and max my speed. About 1250m/s... Then, I will slowly pull up to about 15°-20°, carefull not to stall the wing and bleed off too much speed. Usually changing my pitch will take me to a bit over 20km, where I will ignite rocket engines, and continue the 15°-20° until 35km or so, where I just set it to prograde, and let the shuttle do a gravity turn, and that will level out basically when near/in space.

 

IMHO, the most critical part is getting the climb right in between 12km and 15km. Above 15km (and at speed) the air is too thin to get enough lift from, and its really hard/inefficient to change your direction of travel with aerodynamic surfaces. And the reason this is critical, is if you don't have your pitch high enough, you will not have enough vertical speed to get into space quickly. And burning your rocket motor to plow thru the atmosphere is very wasteful. So you need to get thru the atmosphere as quick as possible, but still maintain the speed needed for orbit.

[GoSlash27]

^ All of this.

 It varies with the jet you're using. The higher the tech of the jet, the higher and faster you should be when you transition to rockets (and accordingly the less rocket DV is needed). You just have to take what it'll give you.

 Designing for minimal drag helps a ton, because you need less jets to get supersonic and that's dead weight you don't have to carry to orbit.

Best,
-Slashy

[Val]

You are also welcome to try some of mine.

They have very different Ascent Profiles. Be sure to read the instructions on the craft pages.

SSTO D-1 Basic	SSTO D-5 Diamond
Craft page and file It's an older model, but it still checks out. It's mostly meant for satellite and probe launches, but if it's not carrying any payload it has range to reach a station up to 500 km orbit.	Craft page and file My latest non-RAPIER SSTO. Lighter than the D-1, but with more range and payload capacity.

[Edax]

8 hours ago, jcthemc said:

Well, after reading RokRoland and Ketatrypts posts, i did some more tweaking and testing, and i've now arrived at this: 

 

So i've made it to orbit, i've got some fuel/oxidizer left for adjustments, but it's not much. Next version i'll probably put on some extra flt-100 tanks. 

Now i'm struggling to get this thing reentered without it burning up, which i've miraculously managed once, only to crash into the water because i was fiddling around and set the power to the engines too low. Upon reentry my real issue is the fact that i can't keep it pitched up. I set my periapsis to about 40~45km, and the during the first part of reentry my pitch will be ok, only to slowly go down to nearly 0 degrees.

I feel like i'm close to where i want the design to be, but it'll take some more fiddling. Any suggestions are welcome.

At high altitude, it's your reactions wheels that maintain most of your pitch control, not your control surfaces.  Attaching more will help keep your plane pitched up during reentry, so you'll aerobrake better.  A good place to stick them is just in front of the engines, since that's a free mk1 attach point.  Just make sure you have enough batteries to keep them running for several minutes, or you'll lose most of your reentry control.

Here's an ol' 6 crew shuttle I use, 100% Raiper free.  I did change the canard with a AVR8 winglet because it was more stable.

Edited February 16, 2016 by Edax

[jcthemc]

That's good to know Edax, i never even consider that. Will have to work that into my design. Slashy, Val, i'll give all your designs a whirl on my next round of SSTO testing. Thanks for all the tips and suggestions.

I spent way too many hours today working on this... i now have a design that almost works even if flown poorly, but i'm kinda burned out on SSTO's right now so i'm going to leave it for a few days. I've got a station to build (my first!) at Minmus, and i'm ready to send my "cruiser" and lander out to Duna. I'm also planning on sending a rover there, but i don't even have that designed yet. Executing all of that will keep me busy for a bit and when i'm done i'll come back to the SSTO.

Thanks for all the help guys, i'm very new to KPS and i can't remember the last time i had this much fun with a game. It's difficulty can be very frustrating at times but i'm really enjoying how great the community is (at helping eachother out.) 

Edited February 16, 2016 by jcthemc

[GoSlash27]

Here's the "Se7en".

SE7EN.craft

Launch profile is as listed above. For reentry, retroburn on the opposite side of Kerbin to establish a 40km periapsis directly over KSC. Shutdown rocket and switch jets to "dry" mode. Maintain 15° pitch throughout. It will drop you right in. There's a reserve of jet fuel after the mission to allow you to fly back to base and land under power.

*edit* While I'm at it, here's the "sixx"; a functional tech level 6 spaceplane.

 It's severely hampered by the unshielded docking port and crappy intake, but it still works.

http://wikisend.com/download/779708/Sixx-2.craft

You have to be super- careful on reentry, as the Mk1 parts don't withstand heating well.

Spaceplanes start to really open up at tech level 8. You get the Whiplashes, wet wings, Mk3 tanker parts, aerospikes, and precooler intakes. Super- efficient personnel transports and heavy tankers become viable.

Best,
-Slashy

Edited February 16, 2016 by GoSlash27

[Dafni]

@GoSlash27 thanks for sharing the Se7en, looks legit. If I can fly it to orbit in a reproducible way I might use it instead of my current design. Or at least use it as a trainer and for inspiration and ideas.

[GoSlash27]

Dafni,

 By all means, use it in good health Especially the "inspiration" part. The important part is the design philosophy; "less is more". If you design for minimal drag in the transsonic region and cut out the stuff that's not absolutely necessary, spaceplanes become much easier to make even at lower tech levels.

Best,
-Slashy

[GoSlash27]

Here's how I wasted my day: Functional spaceplane designs for various career tech levels.

 The transports all ferry a crew of 4 to/ from a station in LKO and have a Kerbal flight crew. The tanker hauls 40t of rocket fuel to LKO and is remote controlled. All of these designs have been flown to orbit and recovered at KSC, but some have not been made fully functional yet (RCS, solar panels, etc).

 They all exhibit the design philosophy I outlined above. Some, like the tanker, have low thrust and more fuel, while others, like the tech level 9 transport, have very high thrust and less fuel.

Best,
-Slashy

[jcthemc]

Those look great Slashy, I'd be very interested in the craft files if you want to share them.

I modified one of Val's designs - added a Turbojet from the B9 mod since i don't have access to the Whiplash yet - and managed to get a small probe into orbit AND fly the SSTO back to KSC. I had some help from Mechjeb for the final approach - lining up the runway can be a pain. The autoland feature in mechjeb does need some help though, and i'm sure i'll learn to complete do it manually in time. Having something functional to work with is great though, now i can start honing my flying skills without having to revert all the time AND do stuff in service of my space program.

Figuring out reentry is an interesting puzzle though. 

Val, i'm wondering though, How do you calculate how much freight a design can carry?

[Val]

1 hour ago, jcthemc said:

Those look great Slashy, I'd be very interested in the craft files if you want to share them.

Agreed. @GoSlash27's designs look great.

 

1 hour ago, jcthemc said:

I modified one of Val's designs - added a Turbojet from the B9 mod since i don't have access to the Whiplash yet - and managed to get a small probe into orbit AND fly the SSTO back to KSC.

I happy that my design was of use to you.

 

1 hour ago, jcthemc said:

Val, i'm wondering though, How do you calculate how much freight a design can carry?

Mostly, I don't calculate. I test it manually. Start by cramming as much as will fit in the cargo bay, then try to reach orbit and see how much dV is left. If necessary, remove some payload until I reach acceptable numbers.

[GoSlash27]

12 hours ago, jcthemc said:

Those look great Slashy, I'd be very interested in the craft files if you want to share them.

I modified one of Val's designs - added a Turbojet from the B9 mod since i don't have access to the Whiplash yet - and managed to get a small probe into orbit AND fly the SSTO back to KSC. I had some help from Mechjeb for the final approach - lining up the runway can be a pain. The autoland feature in mechjeb does need some help though, and i'm sure i'll learn to complete do it manually in time. Having something functional to work with is great though, now i can start honing my flying skills without having to revert all the time AND do stuff in service of my space program.

Figuring out reentry is an interesting puzzle though. 

Val, i'm wondering though, How do you calculate how much freight a design can carry?

jcthemc,

 Not a problem. Just let me know which you'd like. Rather than just handing you a fish, though, I'd rather show you how to fish.  Once you figure out the basics, spaceplanes aren't all that bad. Of course, I say that *now*, but 1.05 will drop any day and probably wreck everything...

Best,
-Slashy
 

[jcthemc]

Slashy,

All of those are above my techlevel at the moment, haha... so i won't have use for most of them for a while. However i'd love to have a look at that tanker.

Edit:

Right now i'm having a problem with the MK2's cargobay.. i can't for the life of me figure out how to attach a probe to a radial decoupler. For some reason the probes get stuck in the cargobay, so the decoupler effective does nothing. EDIT: apparently this is an issue with resized parts. Welp, i don't even want to tell you how long it took to figure that out.

Edited February 19, 2016 by jcthemc

[GoSlash27]

jcthemc,

http://wikisend.com/download/984484/Big8.craft

Release the hounds

Surely you *must* have the tech for at least the TL 6 design? Don't you have the Panther?

Best,
-Slashy

[Val]

I made a TL 6 design, too. It requires 3 nodes that cost 160 Science.

It has RCS, docking port and transports 5 Kerbals.

I hope it can be of use to you. (craft file)

[GoSlash27]

D'oh!

 The .craft file I gave you had the payload removed for reentry testing. I just noticed it this morning when I ran a demo flight for another thread.

Go ahead and top it off for the flight.

Best,
-Slashy

 

[jcthemc]

Little update: I've modded Val's design some more and now have a variation of it that transports Kerbals, 800 units of liquid fuel and a tiny amount of cargo to my Nerv-powered Spacebus that goes from/to my Mun and Minmus stations. Getting that going took some ascent/descent tweaking, so i'm good with SSTO fiddling for a while, until i've completed the next "phase" of my space program atleast. If i do feel like doing a little more, i'm going to dive into picking apart Slashy's designs and tweaking those for my purposes. SSTO testing and flights take up so much time, and i don't want that to be my focus when i have time to play the game.

Most of my space program still consists of parts heavily inspired by Scott Manley's tutorials and his reusable space program series, but i'm ok with that for now. Even with that guidance everything still takes a long time. Once i have Mining ops running on Minmus and am able to haul fuel to LKO, i'm going to dedicate myself to taking my designs to the next level. By that time i should have unlocked some more tech to aid me in that pursuit. I'd love to get a SSTO going that can go to Mun, Minmus and maybe Duna and back.

Thanks for all the help guys, it's very much appreciated.