Single-Turbojet SSTO Spaceplane

[Tarmenius]

I looked around the Forums (admittedly, I may have missed some corners) for an example of an SSTO built around a single Turbojet, like the one pictured above. Having built and seen so many of them before 1.0, I was surprised to find it so difficult to find any. Granted I was struggling myself, but always within about 150 m/s of reaching orbit and I'm not the most skilled pilot by a long shot. But now that I've found success, I figure "If I can do it, then many others could probably do it better (or may already have)."

So, the challenge here will be to, as you may have guessed, build an SSTO spaceplane which uses only a single Turbojet during the atmospheric portion of the ascent. Only stock parts may be used though mods for information, pilot assistance and/or visual enhancement are perfectly acceptable.As this is less of a performance competition and more of a "Lets see all the crazy stuff we can do here" type of challenge, there will be no traditional scoring. However, all who complete the challenge will be listed, and "Top Three" entries could be maintained for various categories (largest, smallest, most delta-v, FAR, etc). Added as necessary, I suppose. The true goal here is to see the range of designs possible while using just one Turbojet. So to get things started, here are the fruits of my struggle:

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Now, lets see what the rest of you talented builders can come up with!

CATEGORIES

(Added as warranted by the submitted designs)

LOWEST MASS (on takeoff):

Foxter "Munchkin 1" (4.41t)

zarakon "Mini SSTO 1.0.2" (5.2t)

georgTF "TurboJet Cheapskate" (8t)

HIGHEST MASS (on takeoff)

Falconer "KerbODactyl" (45.6t!!)

GoSlash27 "TJSST3" (19.6t)

georgTF "Double Trouble" (18.3t)

OUT-OF-THE-BOX DESIGN (In no particular order)

"Rembor III" -- RCS-powered!

"K110 Backlash" -- Double-fuselage

"Double Trouble" -- Twin Nukes!

"Spinoctyl, type J" -- Also twin Nukes! And a trip to Laythe!

"Munchkin 1" -- Not actually a spaceplane

"Shark Mk1" -- Also not actually a spaceplane

"Pogo 2" -- Vertical launch/land

"Fierder 3" -- Clever use of cargo bay

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PARTICIPANTS (STOCK):

NikkyD "Shark Mk1" (4t)

Foxter "Munchkin 1" (4.41t)

zarakon "Mini SSTO 1.0.2" (5.2t)

Postremus "Rembor III" (8.1t) (RCS-powered rocket phase!)

SkyRender "Tourista" (8.4t)

Kuzzter "Pogo 2" (8.7t)

georgTF "TurboJet Orbiter" (9.9t) and "TurboJet Cheapskate" (8t) and "Double Trouble" (18.3t)

Hotaru "Duckling Mark 1" (10.2t)

match "SSTURD" (10.3t)

Starhawk "Rescue 2" (10.7t)

Bill Zarr "X5 & X6" (10.8) & (12.6) respectively

RuBisCO "[Top Secret]" (11t estimated)

Batz_10K "K110 Backlash" (11t estimated)

redsh "single-turbojet" (13.6t)

ABalazs "STJ entry" (15t estimated)

juzeris "Fierder 3" (15.4t) and "Spinoctyl, type J" (25.1t)

SirJodelstein "Rhacophorus" (15.8t)

Rune "Arrowhead" (18.2t)

GoSlash27 "TJSST3" (19.6t)

Falconer "KerbODactyl" (45.6t)

PARTICIPANTS (FAR):

Wanderfound "Thudmeister" (18.9t) and "Minithud" (11t) and "Kerbobee" (CLASSIFIED)

Edited June 7, 2015 by Tarmenius

[Wanderfound]

A FAR entry to get you started:

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Craft file at https://www.dropbox.com/s/obf30cql2tb6z44/Kerbodyne%20Thudmeister.craft?dl=0

[Tarmenius]

Thanks for the submission Wanderfound! Out of curiosity, how do you think the Thudmeister would perform in stock? I've never used FAR so I have no experience to draw from for comparison.

[Wanderfound]

Thanks for the submission Wanderfound! Out of curiosity, how do you think the Thudmeister would perform in stock? I've never used FAR so I have no experience to draw from for comparison.

Something comparable would work in stock. Whether that exact design would, you'd have to fly and see; flying in stock aero is not something I do voluntarily except while waiting for FAR to update. Delta-V requirements are similar; FAR requires a lot more aerodynamic design and piloting finesse, but it also allows a slightly higher jet-powered altitude ceiling.

You can definitely do a low-tech Thud-based suborbital hopper in stock:

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Craft file at https://www.dropbox.com/s/9vptzzhq8knsoaj/Kerbodyne%20Hiflyer.craft?dl=0

[Tarmenius]

[FAR] allows a slightly higher jet-powered altitude ceiling.

Looks like I'll have to load up the Thudmeister to see just how much of a difference there is between the two. And your Hiflyer is one of the designs I iterated through (but with a Turbojet, obviously) to get to the Finch. It performed similarly to the twin LV909 setup I ended with, so finding the "right" ascent might move it beyond sub-orbital.

[Wanderfound]

Looks like I'll have to load up the Thudmeister to see just how much of a difference there is between the two. And your Hiflyer is one of the designs I iterated through (but with a Turbojet, obviously) to get to the Finch. It performed similarly to the twin LV909 setup I ended with, so finding the "right" ascent might move it beyond sub-orbital.

It is doable with just an LV-T800 and a Mk1 LF tank:

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The only stock example that I have at that size is RAPIER based, but would probably work with a turbothud setup:

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[zarakon]

I'm getting close, but still falling a couple hundred m/s short

[Tarmenius]

Wanderfound: Awesome use of the Service Bay! I knew there was a way to use it to launch small satellites...

zarakon: It was a fight to get within 100 m/s of reaching even a 75km orbit. After that, I was stuck at about 50 m/s. The difference was made by shaving off a mere 0.5t coupled with a nice, flat speed phase at about 11-12km.

Edited May 27, 2015 by Tarmenius

[Hotaru]

Most of my existing non-Rapier designs go the opposite route, two turbojets and a single LV-T45. Here's my first attempt at doing it with one jet (stock aero):

Pretty ugly, but made it into a 121x80km orbit and return first time up. (It's not in the rules, but personally I don't count an SSTO as successful unless it can also land safely.) Not optimal, has a surplus of oxidizer. About 200 m/sec left on orbit. Still haven't figured out if the intake pre-cooler actually does anything or not. Will make a better one later. Hopefully prettier as well.

Craft file.

PS. Just noticed I didn't give it a name. Let's call it the Duckling Mark 1.

Edited May 27, 2015 by Hotaru

[Wanderfound]

As well as a bit of intake and a bit of LF, pre-coolers have high heat tolerance and radiative properties. Having it there will allow you to spend more time at speed in the lower atmosphere before overheating the shock cone. Whether or not that is necessary for this ship is a judgement call, though.

If you've got a comfortable heat margin already, swapping the intercooler for a Mk1 LF tank would sort out your excess oxidiser problem (and give you some LF reserve for atmospheric flight after reentry).

[Hotaru]

As well as a bit of intake and a bit of LF, pre-coolers have high heat tolerance and radiative properties. Having it there will allow you to spend more time at speed in the lower atmosphere before overheating the shock cone. Whether or not that is necessary for this ship is a judgement call, though.

If you've got a comfortable heat margin already, swapping the intercooler for a Mk1 LF tank would sort out your excess oxidiser problem (and give you some LF reserve for atmospheric flight after reentry).

Interesting, so they do have at least some cooling effects! I did not know that. I will try swapping it for an LF tank and see what happens.

[Tarmenius]

Most of my existing non-Rapier designs go the opposite route, two turbojets and a single LV-T45..

As do mine. And congrats on completing the challenge! You've been added to the list.

It's not in the rules, but personally I don't count an SSTO as successful unless it can also land safely.

I typically design mine to be capable of return from rendezvous at 100km without refueling. But for this configuration, just getting to orbit in the first place was a challenge for me. I barely got mine to 75km x 75km.

[Starhawk]

Here's a look at my early career craft 'Rescue 2'. Made with parts available fairly early in the tech tree, it can make LKO, rendezvous with a stranded Kerbal, and return to KSC. It's actually a bit light on lift, but it does the job.

Happy landings!

[georgTF]

My entry is the cleverly named TurboJet Orbiter

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WARNING! - This plane is a poor high altitude flier! It satisfies only the following criteria:

- reach low orbit (75km) with as little fuel left as possible (but enough to deorbit)

- land safely*

- takeoff without being too much of an ass

- re-enter without tumbleing into a tailspin

It does fly nicely at low speed in low athmosphere, due to safe landing requirement but high altitude direction change is poor. Other difficulties/disadvantages include a dangerous takeoff. High speed is required and the placement of the gear can cause loss of control. But the advantage is that it's very easy to ascend into orbit.

Link: TurboJet Orbiter

Flight: (The rocket engines are assigned to the RCS group. There's no RCS fuel or thrusters otherwise)

1. On the runway: throttle down, engage RCS to activate rocket engines, stage to activate turbojet, disengage RCS, engage SAS.

2. Full throttle, wait until >70-90 m/s, pull up to take off. (The plane is lazy on takeoff and needs a lot of speed)

3. Pitch up to 60 degrees and climb until 4-5km up. Aim to level off at 6km.

4. At 6-7km level the craft as best as you can and set the angle of attack to 10 degrees. Then leave it alone.

5. Right click on the turbojet to observe thrust. It will rise to about 520.

6. The moment thrust begins to decline, engage RCS to activate rocket engines.

The above was a mistake. Instead:

- Wait until airspeed peaks. When you notice it's started to decline, engage rocket engines.

7. At some point the angle of attack will rise too much. You will have to adjust it back to about 10-15 degrees. Check once at around 40km.

8. Now that the plane is orbit bound, raise Ap to 72km. Cut the throttle and coast up.

9. Circularise orbit at Ap. A few drops of fuel should remain.

If the plane fails to reach orbit try a different ascent profile. The most extreme should be 5 degrees AoA at 5km. This will yield most thrust out of the tubojet at the expense of highest temperatures and loss to drag. AoA higher than 15 degrees will not gain enough velocity leaving the rocket engines with too much work to do (and not enough fuel). Starting the push to space at 10km or higher is likely to waste liquid fuel and will only serve to spare the plane from overheating. The ideal profile should be the one where the plane reaches highest velocity on turbojet power while barely escaping melting due to heat. It can handle 10 degrees AoA at ~6-7km assuming an airspeed of ~300 m/s so try that profile first unless you have a better idea. Winglets will receive most heat but will quickly dissipate it.

Re-entry:

1. At Pe: Perform a retro burn to lower Pe to 35km. This will give a shallow descent with plenty of time to bleed of excess speed.

1a. Aim for a continent. The goal is an unpowered glide with only a tiny bit of low altitude flying possible.

2. Once back in the athmopshere, maintain a high angle of attack. 30-50 is fine and will reduce re-entry heating to manageable levels.

3. Assuming the craft is ~10km, ~200-400m/s and mostly stable, dive down. Do not level off untill about 2km.

4. Below 2km the craft is easy to control. Float down to the ground and pick a flat landing spot.

5. Final approach should be <90 m/s. "Flare" up a few times to kill as much airspeed as possible. Aim to touch down at ~45 m/s or less.

WARNING! - The small gear is very evil and narrow. Make the landing as level as humanly possible. The slower the better.

Other:

- Do not be affraid of low altitude as that is where the plane is at it's best behavior (assuming all fuel has been burned and engines are off).

- Batteries can store a total of 260 power units. Most of this is needed to control the craft during and following re-entry.

- Fuel is a nuisance once the de-orbit burn has been performed. Burn everything.

- Service bay contains: OKTO probe core, small torque wheel, 2 small batteries.

This has been an interesting challenge. Thanks. One more plane that actually works. Now i have 4!

*"Land safely" and "narrow wheelbase" do not go well together. Use quicksave, update life insurance policy, have last will prepared, etc.

Edited June 2, 2015 by georgTF
changed incorrect instructions

[zarakon]

You guys would be better off using Type A nosecones or the tail connector A instead of Type B nosecones at the front of your side nacelles. The type B nosecones don't seem to work correctly, as if they're just flat in the front.

Dual Terriers does seem to be the way to go though, much better than trying to use Thuds. Better Isp, less weight, and probably less drag if you put a good nosecone in front of them (http://forum.kerbalspaceprogram.com/threads/122595-Some-rough-test-results-with-different-nosecones)

[Wanderfound]

The extra gimbal, TWR (good for punching out of the drag zone rapidly) and easy radial mounting (particularly useful for FAR area ruling; the Thuds fill the gap between wings and tail, and have enough nozzle clearance that they can be partially sunk into the fuselage for fine-tuning) are winners for me.

Anyone want to try a direct Thud vs Terrier comparison in stock to see which wins the ÃŽâ€V contest?

[zarakon]

I tried putting each on the sides of my nosecone test rocket (Kickback with 500 fuel)

Terriers attached via Tail Connector A (9990 kg at launch)

top speed 534

top altitude 9271

Thuds (10390 kg at launch)

top speed 483

top altitude 7878

So the Thuds have significantly more drag. There's a little more weight too, but I think the drag is the more significant part. That means you'll spend more fuel during the jet ascent and will have a lower top speed before you have to kick on the rockets. Then of course the Terriers have 345 Isp compared to the 305 of the Thuds. Lower thrust doesn't seem to be an issue for me - 120 is plenty for a plane that's around 9 tons

[Starhawk]

You guys would be better off using Type A nosecones or the tail connector A instead of Type B nosecones at the front of your side nacelles. The type B nosecones don't seem to work correctly, as if they're just flat in the front.

Dual Terriers does seem to be the way to go though, much better than trying to use Thuds. Better Isp, less weight, and probably less drag if you put a good nosecone in front of them (http://forum.kerbalspaceprogram.com/threads/122595-Some-rough-test-results-with-different-nosecones)

Yeah, I ended up abandoning the type B nosecones and replacing them with type A's. That pic is of a slightly older version.

Happy landings!

[SkyRender]

Actually, I made one of the first ultralight SSTOs of KSP 1.0 that used a turbojet instead of a RAPIER. The Tourista SSTO was pretty nifty, and so I've re-created it for this challenge.

Renamed to just the Tourista, it's a compact little beauty.

Since it's so light, it gets off the runway almost instantly!

The jet phase of the program is the trickiest part. It has to get up to around 1050m/s minimum before switching to rockets to get to stable orbit.

Obviously that run I didn't quite nail that goal. It was close though! (Note KER's readouts being completely wrong; it does NOT know what to do with this thing!)

My second attempt went much better.

And finally, a beauty shot. Obviously it can't do much once it does get into orbit, though getting it back down to Kerbin and landed is simplicity itself. As you can see, it has plenty of jet fuel left for atmospheric maneuvering as well! I could have adjusted the fuel margins to be a bit better, but eh.

EDIT: Just to be sure, I landed it.

I figured at first that I might be able to reach KSC. I had quite a bit of fuel left, after all!

That idea went out pretty quick as I did some mental math and realized I'd be landing in the ocean if I tried. So, U-turn!

And here it is landed safely. Jeb seems disappointed that it went off without a hitch.

EDIT 2: Here's the craft itself if you want to try it out! 0 switches between jet and rocket mode and toggles the intakes.

Edited May 28, 2015 by SkyRender

[Tarmenius]

Here's a look at my early career craft 'Rescue 2'.

Out of curiosity, what kind of ascent profile do you use? And does it launch fully fueled?

My entry is the cleverly named TurboJet Orbiter

Few of my craft ever get cool names. It's like naming characters in RPGs... I'm just bad at it. And thanks for the detailed piloting instructions, that's very helpful.

The type B nosecones don't seem to work correctly, as if they're just flat in the front

Well that explains the large amount of drag I experienced in earlier iterations. Also, in the Thud vs Terrier test, I wonder what would happen if a tail connector was used above the Thud in the same manner as for the Terrier. I think I'm going to start up KSP and try it out.

Renamed to just the Tourista, it's a compact little beauty.

It certainly is that, good work!

-----

I've added everyone's entries to the list, and included the masses of each craft (might be useful to know later on). Let me know if I've gotten the numbers wrong, forgotten anyone, or if you have some ideas for fun categories to design for.

[zarakon]

Well that explains the large amount of drag I experienced in earlier iterations. Also, in the Thud vs Terrier test, I wonder what would happen if a tail connector was used above the Thud in the same manner as for the Terrier. I think I'm going to start up KSP and try it out.

Parts only occlude others for aerodynamic purposes via connection nodes. Since the Thud has no connection node at the top, it's not possible to use a tail connector on it in the same manner.

[juzeris]

I'd like to submit an entry too - the Fierder 3 (download). It's a bit on the heavy side for single turbojet SSTOs, weighing 15.4 tonnes at launch, but it still has quite a bit of delta-V left once you get it up there (in the demo attempt I had 1351m/s left once in a 80x80 orbit). Watch those wings though, they get crispy real quick, especially when empty.

[Tarmenius]

zarakon: I guess that explains how wing parts don't obstruct intakes...

juzeris: Impressive work on the Fierder 3! I'm glad to know there's more room for improvement than I thought.

[zarakon]

juzeris: Impressive work on the Fierder 3! I'm glad to know there's more room for improvement than I thought.

it's kind of cheating though, putting the engines inside a cargo bay so they magically don't have any drag

[Tarmenius]

I wouldn't say cheating, exactly. Exploitative, sure. But the goal here is to see how far we can take a single Turbojet, and the techniques required to achieve it. So while the performance itself may not be as impressive as it first might seem, the clever exploitation of physics makes up for it in my mind