Juno spaceplanes

[KerikBalm]

So I saw that the Juno engine has a bit better high velocity performance than the wheesley... and it being the only 0.625m jet engine, I tried to make a SSTO with it.

First I tried a small drone with just 1, I got to space, but nowhere close to orbital velocity.

Then I added more fuel, more jet engines, more rockets... got a higher airbreathing speed, a better LF to O mix... but still came up short:

1950 m/s... I just need to squeeze out about 300 m/s more dV out of it... any ideas?

Anyone suceeded in getting a Juno powered spaceplane to orbit?

Maybe just a pure rocket 0.625m craft would do better... but the small engines have worse Isp and TWRs than the "really good" engines for rocket SSTOing like the aerospike, mammoth, vector, or KR-2L.

I'm sure it would SSTO on laythe, and thats sort of what I wanted... a little scout drone for laythe... but I'd like to be able to get it to orbit from kerbin to make sure it has a good margin, and also simplify getting it to space (rather than trying to fit that into some form of cargobay

Edited November 12, 2015 by KerikBalm

[GoSlash27]

KerikBalm,

I hadn't tried to put one together. It'd need a pretty high proportion of LF&O to work.

Is there a reason you're using 3 Junos? I'd think you could get better performance using just one.

Best,

-Slashy

[WinkAllKerb'']

KerikBalm,

I hadn't tried to put one together. It'd need a pretty high proportion of LF&O to work.

Is there a reason you're using 3 Junos? I'd think you could get better performance using just one.

Best,

-Slashy

might has something to do with take off acceleration reaching fast higher alt with higher angle, my own bet on the the subject, but yup as slashy said most of the time you can get better result with only one, less part, less drag, less wieght/mass worth some more tries adjusting fuel tweakables

[doxlulzem]

Swap out the central Juno for a 0.625m LF+O engines, or maybe, just maybe, see if a monoprop engine would perform better (isn't monoprop lighter than LF+O but just weaker?)

But I'm not that good, so...

[KerikBalm]

KerikBalm,

I hadn't tried to put one together. It'd need a pretty high proportion of LF&O to work.

Is there a reason you're using 3 Junos? I'd think you could get better performance using just one.

Best,

-Slashy

I was struggling to break mach 1 in a shallow climb with just 1 (everything was in one center stack, without the side stacks.

Also, my design has no landing gear, and basically I throttle it up and drop it from a launch stabilizer (maybe I should try launching from the launchpad, as I can have my craft start higher there).

With only 1 juno, I had to light rockets just to get it flying before it colides with the ground.

I was also thinking of 2 junos and 1 spark.

With 3, I could at least break 400m/s and a 15 km apoapsis

I think ultimately, given the low airbreathing top speed, I may end up just with a pure rocket drone..

[MaverickSawyer]

Hmmm... I can think of a cheap and easy way to assist your departure from the launch clamp... the thin 2.5m decoupler has a pretty hefty kick. Put one of those on the back of the drone, and use that to kick you into the air while the engines spool up.

[herbal space program]

I think the Terrier engine is the key to success. The Juno can lift it pretty easily to where I has near vacuum ISP . I've gotten very close now with 1 Terrier + 4 Junos.

[herbal space program]

OK, so I got it to work with a Terrier and 4 Junos. Like I was saying, the Terrier has great vacuum ISP, but it’s just awful at the surface. While the Junos can’t really do much in the way of building up speed, they can lift the Terrier engine to ~7km, where its ISP is already about 285. With that much of a boost, the Terrier can just get it the rest of the way there. I’m sure I can still improve on this performance enough to de-orbit successfully, but I’m too lazy to do that now.

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[KerikBalm]

Yea... I was hoping to do it with only .625m diameter parts though.

Maybe I should have named the thread "0.625m diameter part spaceplanes).

The 0.625m diameter parts don't have good Isp (unless you use an ion engine)... the best is 315, and the best that gives more thrust than an ion engine is 300... compare that to the 345 of the terrier...

[Chakat Firepaw]

Hmmm... I can think of a cheap and easy way to assist your departure from the launch clamp... the thin 2.5m decoupler has a pretty hefty kick. Put one of those on the back of the drone, and use that to kick you into the air while the engines spool up.

If you're going to do that: Add a fuel tank behind the stack separator with a fuel line feeding the craft. That way you can spool up the engines first and still do a 'catapult' launch with a full set of tanks.

[herbal space program]

Yea... I was hoping to do it with only .625m diameter parts though.

Maybe I should have named the thread "0.625m diameter part spaceplanes).

The 0.625m diameter parts don't have good Isp (unless you use an ion engine)... the best is 315, and the best that gives more thrust than an ion engine is 300... compare that to the 345 of the terrier...

I thought you might say that. But you have to admit it doesn’t look bad! I think in addition to the lower ISP with the tiny engines, if you want to go all 0.625m you have to take a hit on wing efficiency as well. I don’t think the Spark alone is quite strong enough to push even the smallest proper wings, so you’re stuck with using less efficient control surfaces for your lift. Perhaps that can all be overcome though, but it’s definitely a tougher problem. Do you mind if the Juno engine doesn’t actually make it get to orbit better than the same rocket would without one?

[KerikBalm]

Do you mind if the Juno engine doesn’t actually make it get to orbit better than the same rocket would without one?

Well, I have a feeling that will be the case...

But.... if it can at least fly under jet power alone, and is capable of landing and taking off, it offers something new...

But that takeoff and landing could be difficult... there's no landing gear for these small craft... a sea-drone may be a good option, it woul work for laythe.

Even without taking off and landing, it would be kind of fun to send a little drone down from orbit... fly around an island on laythe under juno power... then rocket back up to orbit to dock and refuel.

I'd also like to be able to do that on Kerbin.

I think what I have now is good enough for laythe, I just need to multistage it to launch it to kerbin orbit.

[herbal space program]

[quote name='KerikBalm']I was struggling to break mach 1 in a shallow climb with just 1 (everything was in one center stack, without the side stacks.
Also, my design has no landing gear, and basically I throttle it up and drop it from a launch stabilizer (maybe I should try launching from the launchpad, as I can have my craft start higher there).
With only 1 juno, I had to light rockets just to get it flying before it colides with the ground.
I was also thinking of 2 junos and 1 spark.

With 3, I could at least break 400m/s and a 15 km apoapsis

I think ultimately, given the low airbreathing top speed, I may end up just with a pure rocket drone..[/QUOTE]

[FONT=Times New Roman][SIZE=3][COLOR=#000000] [/COLOR][/SIZE][/FONT][FONT="Arial"][COLOR=#000000]What I ended up doing, since they were not kind enough to give us any appropriate landing gear, was to put on the smallest wheels with reverse-mounted small hardpoints, then jettison the gear right after takeoff. I guess that breaks the official SSTO rules, but I think it’s a fair kludge given that the appropriate parts don’t exist and trying to drag the larger ones into orbit is a non-starter. For my part, I tried endlessly yesterday with various combinations of a one-stack design with 1 Juno and one Twitch or 6-8 Spider engines mounted radially. With the best Twitch configuration, I *almost* made it to LKO, managing one time to get to a 72km apoapsis and 3km periapsis (pictures later maybe). In that process, I think I also identified the Delta Deluxe winglet as the optimal main wing. That’s a little better than KerikBalm posted upthread, but still a good 100-150m/s short of making orbit. I’m getting a little tired of flailing away at this problem after spending half the day on it yesterday, but it’s so tantalizingly close I think I might just try with a 3-stack, 1 Spark + 2 Juno configuration before giving up. The Spark has just a little better thrust and ISP than the Twitch, but I don’t know if that will be enough to offset the added weight and drag of having a 2+1 tri-stack. Lastly, I think I can say that those small circular intakes are significantly draggier than the structural intake, although of course swapping those for nosecones makes everything weigh more.[/COLOR][/FONT]
[FONT=Times New Roman][SIZE=3][COLOR=#000000] [/COLOR][/SIZE][/FONT]

[Cunjo Carl]

   It took a surprising amount of effort, but I got it! I've orbited several single stack Juno SSTOs, each design with a scrape of fuel to spare. They're all 0.625m parts too, so they're super cute!

Control Systems
    I came to the many of the same conclusions as @herbal space program, but one of our key differences was choice of control systems. I wound up using reaction wheels, and found the small one pleasantly but barely sufficient to control flight. This saved me from heavier/draggier solutions such as ailerons or the Delta Deluxe.

Wings
    I love the Delta Deluxe, but it has a terrible intrinsic lift/drag (L/D) coefficient as a tradeoff for its convenient control surfaces. Using the reaction wheels instead freed me to use the Small Delta Wing and the Wing Connector Type D, with slight preference for the flight characteristics of the small delta. The small delta's high intrinsic L/D counterbalances the fact it's about 30% too big for our purposes. On the other hand, the structural type D's low weight counterbalances its middling L/D and slightly too small size. Both will get to orbit, though! Because I'm on keyboard, I tilted the wings up about 10 degrees from true, so I could just set the SAS to prograde and let the ships lift steady!

Rockets
   I ultimately used a single stack Juno with 1 twitch hanging off. Because the COM moves so much during the final burn, it's a little tricky to keep on target, but rapidly pounding the keyboard helped... As an alternative solution, a spark can be placed just behind the Juno, and then we can slightly clip the Juno inwards. It doesn't take much to get it within the spark's damage offset, and then you have your very own mini rapier! These were my favorite to fly, but opinions on clipping may vary.

Gear
   I concluded the same as Herbal, that landing gear's gotta go! There's just nothing appropriate for runway landing teeny tiny SSTOs yet. It's ironic because together with the decouplers, the landing gear comprises nearly half the craft's cost, but into the ocean with them!

Intakes
   I found the low drag of the structural intake invaluable, despite it's slightly higher mass. I didn't try it exhaustively, but things started going nicer when I ditched the small circular intake. Both of the intakes provide 10x too much air, in any case!

Flight Path
   The Juno spaceplanes have two advantages over rockets, first being their ability to lift the craft up to where it's low-pressure/low-drag basically for free, and the second their L/D ratio preventing losses to gravity during that long trek up to orbital speeds. Fast space planes can also develop some of their orbital speed while still air breathing, but Junos are limited by their anemic TWR to fairly low speeds when pushing fuel. I just cut speed development as a loss, and instead focus on the free initial lift and the free gravity repulsion while speeding up instead. The flight path is fairly forgiving, just lift up to 8-10km at a 10-20 degree angle, and then burn with the chemical rocket, too. After that, raise the Ap to 75km, and enter orbit in the normal way. It's an easy flight for such a difficult-to-tune design!

 

 

 

The next question is, can it be scaled to a 2 or 3 stack while removing extra wing/intake to make space for a payload.... A Teeny Tiny Payload!

Edit: I just noticed this was the discussion section, not the challenge section. So I should address the @KerikBalm's original question of how to make that space plane fly more. Should be simple, swap the aileron wings for small deltas or structural Ds, and swap the control surfaces for basic fins and a tiny reaction wheel. That oughta do it! Ahem, six months late, but better late than never I hope the Laythe trip went nicely in the meantime. Cheers!

Edited June 1, 2016 by Cunjo Carl

[awfulhumanbeing]

If I'm not mistaken, Juno can't go past Mach 2 or something. Anyway, it can't go hypersonic so maybe your plane misses what most SSTOs have - high speeds on low altitudes.

[Van Disaster]

I tried it but in the end it was basically a rocket craft, so I just use Junos for recovery to the runway on the way back down. You can build some stupid monsters with the lower tech engines anyway ( note the thread mentioned spaceplanes rather than SSTO - this one certainly is a Juno spaceplane! )

Now I've seen someone SSTO one I'll have to have another go, that was worth the necro I think. I'd not dismiss the Wheesley too soon though, you can get more altitude out of it & that matters for rocket efficiency.

Edited June 1, 2016 by Van Disaster

[Cunjo Carl]

16 minutes ago, Van Disaster said:

Now I've seen someone SSTO one I'll have to have another go, that was worth the necro I think. I'd not dismiss the Wheesley too soon though, you can get more altitude out of it & that matters for rocket efficiency.

If the Juno can do it, the Wheesley should, too! The most important factor is engine TWR, and they both rock a *ahem* 8. If you're sporting one Wheesley 6 twitches should do, or (even better) two Wheesleys and an aerospike. Sweet plane, by they way!

 

24 minutes ago, awfulhumanbeing said:

If I'm not mistaken, Juno can't go past Mach 2 or something. Anyway, it can't go hypersonic so maybe your plane misses what most SSTOs have - high speeds on low altitudes.

Because whiplashes and rapiers have 30-40TWR, they can actually develop orbital speed while in atmo. Our anemic little jets are just good for the trip up out of the thick of the atmosphere, which is nice for developing orbital speed without air friction losses. Also, the wings provide lift, which is a cheap counter to gravity, so even if it's slow an SSTO plane can be efficient by following a shallower trajectory than a typical gravity turn. Is it worth it? Heavens no! Is it fun? Yep .

[Streetwind]

@Cunjo Carl - great effort, but it technically is not a "SSTO" if you drop something during ascent. Even if that something is the landing gear

(It's still a successful Juno-powered spaceplane though, and that's technically what this thread is about.)

[KerikBalm]

On 6/1/2016 at 6:35 AM, Cunjo Carl said:

Using the reaction wheels instead freed me to use the Small Delta Wing and the Wing Connector Type D, with slight preference for the flight characteristics of the small delta. The small delta's high intrinsic L/D counterbalances the fact it's about 30% too big for our purposes. On the other hand, the structural type D's low weight counterbalances its middling L/D and slightly too small size.

...

As an alternative solution, a spark can be placed just behind the Juno, and then we can slightly clip the Juno inwards. It doesn't take much to get it within the spark's damage offset, and then you have your very own mini rapier! These were my favorite to fly, but opinions on clipping may vary.

Gear
   I concluded the same as Herbal, that landing gear's gotta go! There's just nothing appropriate for runway landing teeny tiny SSTOs yet. It's ironic because together with the decouplers, the landing gear comprises nearly half the craft's cost, but into the ocean with them.

*grumbles about new forum format, cant remove iamge from quote*

Well, I came to many of the same conclusions as you (this is an old thread)

^ I later replaced the wings on this one with the structural D I think... the small delta like pieces. Also I clipped the spark and the juno at the back...

This isn't my most recent, but I don't want to bother uploading pictures now:

I too, jettison the landing gear, but it lands with chutes on the runway for 100% recovery. Also note the Sepratrons to get it up to takeoff speed very quickly.

My most recent design, in addition to the changed wing (I should try the intake you recommend), I made the landing gear differently... or rather... the rocket sled. The plane has a positive AoA while on the rocket sled... the rocket sled has small wings with negative AoA to keep it on the ground. When the plane decouples, the sled's parachutes deploy... it never leaves the runway... so its basically just a catapult.

If I don't count the catapult as a stage because it never leaves the ground/runway, it made orbit as a SSTO, just barely...

Edited June 2, 2016 by KerikBalm

[herbal space program]

Well done, Cunjo Carl, but did you do this in 1.1.2? If so, then I need to pull out my old entry and see how it does now. They really lowered the drag, especially in the upper atmosphere, vs. 1.0.5. My Mk1 regular SSTO is getting almost 1 km/s more dV on orbit in 1.1.2 than it did in 1.0.5, and when I did this in 1.0.5 I fell only 150 m/s short of of circularizing.....

Edited June 1, 2016 by herbal space program

[Vanamonde]

This exchange of spacecraft has been moved to the Spacecraft Exchange. 

[Van Disaster]

Was rather awkward under FAR... until I used some proc parts ( tanks + wings ). Some fuel balance/pumping issues but in orbit with enough dV to get nearly to Mun.
 Probably optimizable too. Might be a neat way of doing science satellites, I think, although I don't have the minature rockets in career yet & by the time I do I doubt I'd want Kerbin orbit science anyway airlaunching one/adding a booster stage/sticking it in a fairing on a normal rocket alá X-37 would probably get it to Minmus, so maybe that would be worth it. The fairings & science gear from Sounding Rockets seem an obvious fit here, although I'd really like a 0.625m cargo bay ( I guess I can knock one up if there's nothing available ).

I'm so tempted to put a command seat in an open cockpit...

Edited June 1, 2016 by Van Disaster

[AeroGav]

Looks like a few of you have a working SSTO at this point, but I'll share this as a data point, my attempt at a Juno Spaceplane.      I've decided to call it the Icarus, can't think why

https://kerbalx.com/AeroGav/Icarus

One terrier, 3 ft 400 tanks and , wait for it, 14 Juno engines !

I did start off with 10, but was unable to bust the sound barrier,  I added another pair,  but then the engines hung unevenly off the wing, it must have an odd number of engines each side so that the engine which is coupled to the wing has the same number of neighbours hanging off it's left as it's right side.

So, 14 it was.   This gets me to mach 1.5 at nearly 15km airbreathing.  

Edited June 1, 2016 by AeroGav

[Cunjo Carl]

11 hours ago, Vanamonde said:

This exchange of spacecraft has been moved to the Spacecraft Exchange. 

Thank you, moderator!

 

12 hours ago, herbal space program said:

Well done, Cunjo Carl, but did you do this in 1.1.2? If so, then I need to pull out my old entry and see how it does now. They really lowered the drag, especially in the upper atmosphere, vs. 1.0.5. My Mk1 regular SSTO is getting almost 1 km/s more dV on orbit in 1.1.2 than it did in 1.0.5, and when I did this in 1.0.5 I fell only 150 m/s short of of circularizing.....

Thanks! I did this in 1.05, because I haven't been able to get KER to work in 1.x yet, and it's such a necessity for making little tweaks. I didn't know about the drag, but it actually makes a lot of sense in retrospect! One of my crafts just lost a race that TWR suggests it should have won handily! Also, I can empathize with the frustration of being a few m/s short of orbit, I once sunk two hours into a ship that was very reliably 50m/s short. I actually made a perfectly circular 50km orbit once, and finally decided for a redesign. You should try your ship again in 1.1 in any case and see how it fares!

 

20 hours ago, KerikBalm said:

*grumbles about new forum format, cant remove iamge from quote*

 I made the landing gear differently... or rather... the rocket sled. The plane has a positive AoA while on the rocket sled... the rocket sled has small wings with negative AoA to keep it on the ground. When the plane decouples, the sled's parachutes deploy... it never leaves the runway... so its basically just a catapult.

If I don't count the catapult as a stage because it never leaves the ground/runway, it made orbit as a SSTO, just barely...

 

Rocket sleds. Genius! I went ahead and made a launch platform for mine, too. It's not rocket powered, but I've been calling it a rocket sled anyways because it sounds so cool. 'Grats on making SSTO, by the way. Also, you can remove pictures by right clicking and selecting cut, I found after much trial and error. More on the launch platform follows.
 

Spoiler

 

Though it doesn't take huge mechanical skill to build a rocket sled in KSP, it's hard to deny they're awesome.  I constructed a fully reusable 'rocket sled' unpowered launch platform instead of dumping landing gear in the sea, which I think brings this much more inline with the spirit and definition of SSTO. The brake command has a short delay time, so you can reach takeoff velocity, apply the brakes, decouple from the sled and take off while the sled rolls to a stop. You can also quickly change focus to the sled and forlornly watch the plane fly away.... bye!

 

 

 

 

Edited June 2, 2016 by Cunjo Carl

[KerikBalm]

Well.... I'm reaching orbit (about 75x75... or more like 77x73) with about 80 m/s to spare now, with an inline battery and an oxstat... tommorrow I'll try adding a thermometer and an antennae.

I added 1 more pair of sepratrons on my rocket sled... facing backwards, that activates upon decouple.

I feel a bit cheaty using the clipped spark... but I don't know if the margins for my design and ascent profile (it may not be optimum) could tolerate the slight drag increase, the ~12% rocket thrust decrease, and the ~3.3% Isp decrease.

Anyway... I find myself lighting the rocket at Almost exactly 200 m/s and 10km... but my TWR is barely 1:1 when that happens.