Juno spaceplanes

[AeroGav]

4 hours ago, KerikBalm said:

 

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.

1:1 is not the same thing in an airplane as a rocket though.  Less than 1:1 in a rocket means you start falling back to earth.   In an airplane,  TWR needs to be better than lift/drag ratio, that's all.   So if lift drag ratio is 3 to 1 then so long as your TWR is better than 0.333 to 1 you can keep climbing.   Or to express another way,  thrust just needs to be higher than drag while in steady flight (one that isn't ballistically arcing downwards)

Can you improve your L/D ratio by adding more or less wing? Adjusting AoA or your ascent profile?    For supersonic flight 3:1 is great, but at 200m/s you should be seeing 6:1 or better.  At 100m/s you can get over 10 to 1

[KerikBalm]

Yes, as I said, I was getting to orbit with >80 m/s left.... so obviously I was climbing

I'm just saying that a higher TWR would have been nicer so that the climb rate could be better, and less dV would be lost to drag.

[Van Disaster]

If anyone's not opposed to mods & is actually making good use of these rather than building for fun - SoundingRockets ( Roverdude ) has a .625 fairing/truss *and* a tiny aerospike, and SurveyTransponder ( taniwha ) has a .625m cargo bay. If you feel the need to legitimise your mod use, both are Squad employees I'm using mine as science return devices from stations.

Edited June 3, 2016 by Van Disaster

[KerikBalm]

what would you even put in a 0.625m cargobay?

My current SSTO can fit in a mk2 bay (but I don't really have a good way to attach and detach it)... but I can't really think of much to put in a 0.625m bay... some small science experiments and an antenna? a surface attach battery? I think an inline battery would be more mass efficient than the cargobay+battery.

[Van Disaster]

TarsierSpaceTelescope comes with a science storage part which is definitely not re-entry proof - and SoundingRockets also has some minature experiments ( but I tend to strap those to craft doing other things anyway ).  I'm sure there's other things around.

[KerikBalm]

I'm tempted to rescale some parts,and have 0.3125m parts... for a tiny probe launcher ... I'm just envisioning the dV I could get starting with a 3.75m stack... going down to a 0.3125m stack... perhaps journeys to the outer planets (in the OPM mod) wouldn't take so long...

[Van Disaster]

3 hours ago, KerikBalm said:

I'm tempted to rescale some parts,and have 0.3125m parts... for a tiny probe launcher ... I'm just envisioning the dV I could get starting with a 3.75m stack... going down to a 0.3125m stack... perhaps journeys to the outer planets (in the OPM mod) wouldn't take so long...

Heh, well, if you want something really cute...

SoundingRockets + stock ( and, er, GPOSpeedFuelPump for crossfeed without pipes ). Slightly offtopic though
Could do with some smaller radial decouplers...

Edit: crossfeed pumping confuses the nuts out of the dV calc:

So yep, go fiddle & produce minature stuff some more linearily packaged/folding instruments might be handy anyway.

Edited June 4, 2016 by Van Disaster

[herbal space program]

FWIW, I'm finding it fairly straightforward to make orbit with this tri-stack  rig:

 

 

 

Disclaimer 1)   I'm still jettisoning the gear, although I have launched other versions off a sled and there's no reason I couldn't do that with this one as well.

Disclaimer 2)  I have a circular intake clipped backwards into the Spark engine to shield it from drag. Looking at the F12 drag overlays, I found that the small circular intakes dramatically reduced the drag both front and back on my rocket stack.

I think I would probably improve it by adding one more pair of Oscars to the side stacks. I found that the added TWR of clipping a Twitch engine into the Spark stack more than made up for the extra weight and drag. It seems to me that to make orbit, you need to be able to take off at near a 45 degree climb from the ~10km operational ceiling of the Juno to above 20km. Flying sideways through that slice of the atmosphere with a low TWR really saps your dV, but with both of those engines on the back of this plane, it was easy to climb at 40 degrees while still accelerating.

[He_162]

10 hours ago, herbal space program said:

FWIW, I'm finding it fairly straightforward to make orbit with this tri-stack  rig:

 

 

 

Disclaimer 1)   I'm still jettisoning the gear, although I have launched other versions off a sled and there's no reason I couldn't do that with this one as well.

Disclaimer 2)  I have a circular intake clipped backwards into the Spark engine to shield it from drag. Looking at the F12 drag overlays, I found that the small circular intakes dramatically reduced the drag both front and back on my rocket stack.

I think I would probably improve it by adding one more pair of Oscars to the side stacks. I found that the added TWR of clipping a Twitch engine into the Spark stack more than made up for the extra weight and drag. It seems to me that to make orbit, you need to be able to take off at near a 45 degree climb from the ~10km operational ceiling of the Juno to above 20km. Flying sideways through that slice of the atmosphere with a low TWR really saps your dV, but with both of those engines on the back of this plane, it was easy to climb at 40 degrees while still accelerating.

I LOVE THAT ENGINE NACELLE YOU MADE AT THE REAR!

lol, this thread is just awesome, I wanna see more of these

[Van Disaster]

22 hours ago, He_162 said:

lol, this thread is just awesome, I wanna see more of these

Well mine aren't stock, but I'm using them for satellite/scanning contracts a fair bit the thread has inspired me to start on a bunch of parts ( couple of different enclosed bays and a tiny ramjet, so far ). Not sure my modelling is up to stackable minature solar panel trees yet but I'll give it a shot...

[He_162]

23 minutes ago, Van Disaster said:

Well mine aren't stock, but I'm using them for satellite/scanning contracts a fair bit the thread has inspired me to start on a bunch of parts ( couple of different enclosed bays and a tiny ramjet, so far ). Not sure my modelling is up to stackable minature solar panel trees yet but I'll give it a shot...

Small things is interesting..

 

There should be a mod called "Small Things" Consisting of 0.625 and smaller wing parts, small little bays, antannaes, engines, ramjets, and a little airbreak or so too, that would be really cool.

[Van Disaster]

1 hour ago, He_162 said:

There should be a mod called "Small Things" Consisting of 0.625 and smaller wing parts, small little bays, antannaes, engines, ramjets, and a little airbreak or so too, that would be really cool.

"Little Things".... yes, quite tempting. I'll stick with b9 pwings, but there are a lot of other useful things that could be made. I like the idea of a nosecone which opens up to reveal a docking port.

[He_162]

1 hour ago, Van Disaster said:

"Little Things".... yes, quite tempting. I'll stick with b9 pwings, but there are a lot of other useful things that could be made. I like the idea of a nosecone which opens up to reveal a docking port.

Not that time is wasted making such things, why not have it? Anyone could do it with the right knowledge, and there is no shortage of people willing to learn, so I suppose everything is possible.

 

Someone should make a efficient Juno powered SSTO that can take 5 tons to orbit or something like that, that would be really amazing.

[KerikBalm]

but my juno spaceplane is about 5 tons total!

[He_162]

51 minutes ago, KerikBalm said:

but my juno spaceplane is about 5 tons total!

So put three of them together, and put a 5 ton cargo at the front or something.. lol

[KerikBalm]

nah, this isn't taking much into orbit:

The only instance of clipping is the juno and the spark... but I think a pair of Twitch engines could do better because of TWR issues...but that Isp loss isn't great...

If I could get it to take off from the water too... it would make for a re-usable spaceplane, especially on laythe (I may have to give it another OX-Stat perhaps)

[herbal space program]

22 hours ago, KerikBalm said:

nah, this isn't taking much into orbit:

The only instance of clipping is the juno and the spark... but I think a pair of Twitch engines could do better because of TWR issues...but that Isp loss isn't great...

If I could get it to take off from the water too... it would make for a re-usable spaceplane, especially on laythe (I may have to give it another OX-Stat perhaps

Are you sure that structural intake is the way to go? I started using one based on your design, but I couldn't get past 300m/s near the ground with it. When I switched to the small circular intakes, I could go much faster. Based on the F12 drag overlays, the circular intakes, in front on the Juno stacks and front-and-back on the Spark/Twitch stack, really reduce drag to near nothing. The plane I posted above can reach 340+ m/s below 3500m. I dunno, maybe they changed the behavior of these parts since 1.0.5?

Edited June 12, 2016 by herbal space program

[KerikBalm]

well, I was following someone elses lead... my earlier one had a small intake... but I had to clip it back ot protect it from the heat... so that intake is less exploity (though I'm still being exploity with the clipped spark, which I hope to replace with 2x twitch)

[herbal space program]

8 minutes ago, KerikBalm said:

well, I was following someone elses lead... my earlier one had a small intake... but I had to clip it back ot protect it from the heat... so that intake is less exploity (though I'm still being exploity with the clipped spark, which I hope to replace with 2x twitch)

Well considering what we're trying to do here, I think just a little part clipping is fair enough! I was having a lot of problems with my leading circular intake exploding as well, but it didn't happen every time. I think you'll probably find that if you go back to the circular intake and add that extra Twitch like you were saying, you'll have enough rate-of-climb after rocket ignition to keep your nose from blowing off.

[Cunjo Carl]

On 6/12/2016 at 7:54 AM, herbal space program said:

Are you sure that structural intake is the way to go? I started using one based on your design, but I couldn't get past 300m/s near the ground with it. When I switched to the small circular intakes, I could go much faster. Based on the F12 drag overlays, the circular intakes, in front on the Juno stacks and front-and-back on the Spark/Twitch stack, really reduce drag to near nothing. The plane I posted above can reach 340+ m/s below 3500m. I dunno, maybe they changed the behavior of these parts since 1.0.5?

Woops, Circular is better.
Ohhh... My mistake, circular intakes are the way to go! I was the one that brought radial intakes + nose cones into vogue, but it turns out they're a bit inferior. Since I switched over to 1.1, I've been flying blind without AeroGui to measure drag, and I misread the F12 drag overlay. I didn't take into account that the nose cones are a bit longer than the intakes, so their drag arrows are a bit longer than they look. I just retested with my nearly-working nose cone design, and turned it into a barely-working circular intake design! A very, very welcomed improvement

 

The new ship
To my gleeful surprise, it hauled up a science-festooned probe that went into interplanetary space! But boy, it was a close call. In the end, I needed to use up most of the payload's fuel to get the SSTO into orbit. I've only tried this design+flight-path once, so hopefully it can be optimized. Of particular note, the central stack doesn't have a clipped spark, so the ship is rocking 5 Junos and 4 Sparks with 7 Oscars per Spark. I still don't have a good feel for where we should be with the Juno/Spark/Fuel ratios, but in retrospect that fifth Juno is as heavy as my entire delivered payload! For control, I fell back on ailerons, because I just wasn't getting enough torque out of the reaction wheels for this bigger ship. I found two ailersons and a reaction wheel worked sufficiently well. Finally, for the flight path, I've been holding at 12 degrees off horizontal in low Juno-only flight, and ~20 degrees in high Spark-assisted flight. It feels nice, but I don't know how optimal it is.

It was very gratifying to finally get a probe out there, though! My dream of rocketing a Kerbal into LKO with Junos is looming.

Would you like lists and plots?
To make this ship, I sifted through parts and physics files to make a few lists and plots that've been occasionally helpful. I can post some of the findings if anyone here wanted. It would be space consuming though, so I'd probably need to figure out how to toss it into a spoiler tab...

Took a break to cook up a silly Juno Plane
Last up, after really struggling with this design a couple weeks back, I decided to take a break and just make a supersonic Juno plane with a Kerbal perched on top. I had a great time flying it and writing the flavor text for the screen shots. If you want to check it out, the post is halfway down the front page of this challenge:Supersonic plane challenge (Highest number of likes wins.

Cheers!

Edited June 15, 2016 by Cunjo Carl
Minor readability changes