Jupitec 7 AKA "The Flying Buttress"

[LitaAlto]

When KSP administration approached Cuzican Aerospace with their Jet Propelled Test Vehicle project, and their initial prototype, the JPTV-1, we asked them to stop trying to design and name ships and let us handle making it awesome.

Then we asked for the specs.

We had to make a SSTO craft capable of landing on Minmus and returning safely. And they were keen on air-breathing engines for fuel economy.

Which we did. To spec.

And it just so happened that, during the development phase, we went from a rocket with jet engines on the fins to a craft with massive air-breathing nacelles and a strong resemblance to a Kothig castle.

And thus the Flying Buttress was born.

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It should be able to reach an 80 km orbit around Kerbin with enough fuel to transfer to Minmus, land, and return safely.

The RAPIER engines are on automatic by default. It is recommended that you shut the air intakes (Action Group 1) when the engines switch from air-breathing to LOX. Doing so reduces drag noticeably, improving delta-V.

If you prefer, you can redo the action groups for manual switching of air-breathing and LOX modes, tied into the closing of the intakes.

The mobility enhancers (ladders) are keyed to the Gears action group as well--a legacy from earlier designs where landing gear and ladders would deploy at the same time.

Further testing will be done on the potential of shallower ascent curves allowing for greater speeds during air-breathing ascents.

Update 1: I'm able to achieve 2166 m/s in leftover dV if I use a 20-degree ascent angle, versus 1741 m/s with a 40-degree ascent angle. Will soon try a hybrid--go 9 km straight up, then go on the 20-degree ascent until the engines cut, then switch to 40-degree to clear atmosphere and reduce drag effects.

Update 2: Thanks to the advice of Radam, I've got a more optimal launch plan. If you launch straight up, then turn at 4 km and maintain (roughly) a 100 m/s vertical velocity until flameout/switchover, you can conserve about 3200 m/s in delta-V, ample to land on the Mun and return safely.

I've also got a variant, the Jupitec 7-A, which effectively replaces the Jupitec 7.

Download the Jupitec 7-A from Gameframer.

(Note: Gameframer is in alpha, and its delta-V estimates should be taken with a grain of salt.)

Edited April 13, 2015 by LitaAlto
Updated with testing results

[Mad Rocket Scientist]

Nice!

Can it land on the Mun too?

[LitaAlto]

Nice!

Can it land on the Mun too?

Thanks!

I haven't attempted a Mun landing yet.

I think the 7 doesn't have quite enough delta-V for the task, but I'm experimenting with ascent paths to shave off some more delta-V beforehand. I also want to completely exhaust the fuel at some point so I can determine how much oxidizer I should (further) leave behind.

If that doesn't get me enough, I'll probably come up with another iteration with a bit more fuel and see if that works.

[meve12]

I think Jupitev is better to say.

[Rath]

The return of winglet landing legs!

[LitaAlto]

I think Jupitev is better to say.

"Jupitec" has that "tec" syllable at the end, which makes people think of technology.

What does the "v" do for you?

- - - Updated - - -

I did some testing of the Jupitec 7 "Flying Buttress" to see if I could conserve delta-V with a shallower ascent curve. Since the Flying Buttress breathes air during the first part of the ascent, keeping it in atmosphere for as long as possible helps to build speed, which leads to needing less delta-V to complete the orbit. Of course you still have to deal with gravity and drag, so you can't go too shallow.

Using MechJeb to edit the ascent curve, I ran a launch multiple times, each with a different turn shape. Here are the turn shape percentages, and the final post-orbit delta-V estimates I get. The lower the turn shape percentage, the flatter the ascent curve, and thus the more time is spent in the region where intakes still work.

40% -- 1741 m/s

35% -- 1825 m/s

30% -- 1929 m/s

20% -- 2166 m/s

15% -- 2184 m/s

I wish I had done a 25% turn shape--but it's pretty obvious to me its results would be somewhere between 2029 m/s and 2066 m/s>

And of course, as you get under 20%, drag and gravity starts to take a toll. 15% can get you a bit more delta-V--but not much. I did attempt a 10% turn curve, but it became clear the craft was struggling to ascend at that point, offsetting any speed gains I could've had.

[Radam]

I wish I had done a 25% turn shape--but it's pretty obvious to me its results would be somewhere between 2029 m/s and 2066 m/s>

And of course, as you get under 20%, drag and gravity starts to take a toll. 15% can get you a bit more delta-V--but not much. I did attempt a 10% turn curve, but it became clear the craft was struggling to ascend at that point, offsetting any speed gains I could've had.

You could always fiddle with the curve manually while in flight. Like after turning over at 10km, you have had set the curve to be 25%, when vertical velocity gets over 100, you reduce it. When rapiers switch over, you turn back upwards.

Edit:

My first attempt at flying this into orbit with mechjeb... 2607m/s left over.

Ive built launchers with rapiers since like 2 years ago, before that it was turbos and spikes... Anyway, my latest iteration has 15 rapiers, weighs 120t on launchpad and lifts 60t to LKO.

I did actually try your Jupitec version 10. IMO its a bit light, could be about 80t and still get into orbit. But i did get into orbit with 2100 m/s left over.

Edited April 5, 2015 by Radam

[LitaAlto]

You could always fiddle with the curve manually while in flight. Like after turning over at 10km, you have had set the curve to be 25%, when vertical velocity gets over 100, you reduce it. When rapiers switch over, you turn back upwards.

Edit:

My first attempt at flying this into orbit with mechjeb... 2607m/s left over.

http://cloud-4.steamusercontent.com/ugc/532889637745163980/C68A719D9D26AB4D8ABCFFD32482FC81B108C480/

Ive built launchers with rapiers since like 2 years ago, before that it was turbos and spikes... Anyway, my latest iteration has 15 rapiers, weighs 120t on launchpad and lifts 60t to LKO.

I did actually try your Jupitec version 10. IMO its a bit light, could be about 80t and still get into orbit. But i did get into orbit with 2100 m/s left over.

Very nicely done! I'm interested in trying your flight trajectory--so you're flying to 10 km, then a 25% curve dropping to... 20% I'd guess? Then go back to a higher percentage curve. Is that right?

The Jupitec 10 was an attempt to maximize delta-V for Mun landings. But if you're able to get 2607 m/s with the Jupitec 7, that implies the 7 can actually reach the Mun under ideal circumstances.

[Radam]

Well i was staging the engine mode switching aswell.

Craft was following mechjeb ascent curve. Which started from 25% dropping back down to even 7% level while keeping vertical speed at about 100m/s. When air becomes too thin for all engines, i switch first set of them and set the curve back up.

Btw, try loading the craft at about 8t per rapier.

I would still detach the cockpit and use a nerva engine for munar trip. Could still dock back and land with atmospheric engines.

Edit: im sorry but version 10 has less Dv than 7.

Main problems:

-not enough fuel, aim for 12m/s2 acceleration from the pad, v10 has like 15

-not enough intakes. The ones you are using have area about 0.0025 m2 while regular ram intakes have 0.01m2. So your craft has in the end just over one ram intake worth per engine. My designs usually have about 2 to 3.

Basically try 8 fold simetry, shock cone intakes with some more of those high speed ones. Aim for 64t craft and avoid heavy parts without fuel in them.

Edited April 6, 2015 by Radam

[Radam]

Speaks for itself. Only modifications I did were swapping the upper small tank with 3 liquid fuel tanks, and some action groups. I actually need more liquid fuel...

From 10km to until air runs out im keeping my vertical speed at 90m/s with lowering or increasing curve % in mechjeb.

Im bad at mun landings, specially in the dark.

Edited April 7, 2015 by Radam

[LitaAlto]

Thank you for all the advice.

Edit: im sorry but version 10 has less Dv than 7.

Don't be sorry, that was a first stab and is nowhere near release-ready. I may not immediately replace the adaptors in the 10 though, since I'd be tempted to provide some sort of fairing no matter what. Maybe I'll wind up using struts, as little as I like doing so, just to reduce weight a bit. But I'll certainly increase the fuel.

Also, I wasn't sure what exactly would constitute "the right amount" of air intakes. TBH I've already been accused of airhogging, with the preliminary photos of the 10 I released, and you're telling me I don't have nearly enough, so...

http://cloud-4.steamusercontent.com/ugc/532889637751635261/CA8B605358A7D142A1F896FEBB1AA8DB11666F24/

Speaks for itself. Only modifications I did were swapping the upper small tank with 3 liquid fuel tanks, and some action groups. I actually need more liquid fuel...

Which tanks? And what changes did you make to the action groups, if I may ask?

I've considered making a separate Munar lander--but if I go that route, I may as well set up fueling stations and use Jupitec 4-ADs for all Kerbin system traffic. (Which is actually the direction I'm leaning, in terms of game play, provided these crafts won't need much retuning after 1.0 drops.)

[LitaAlto]

Also: OMG I'm getting 3200 m/s delta-V left over after some of my test orbits with a slightly modified version of your ascent--vertical to about 4 km, then maintain roughly 100 m/s vertical speed (somehow) until air runs out. Aside from swapping some of my FL-T200 Fuel Tanks for Mk1 Liquid Fuel Fuselages, I've made no other changes.

...Although I am having some problems landing it now, without the thing flipping over the wrong way and tearing apart upon full chute deploy. I'll figure it out though.

[Radam]

Nice!

I have action groups set for manual switching of the engines. So that not all engines switch to rocket mode at once.

As for air hogging, stock Aeris 4 has 1 ram intake and 2 radial air intakes per engine. Which amounts to 0.022 intake area per engine. As structural intakes you are using only have 0.0025 intake area each, aeris 4 would need like 16 of them...

I think the site you are using to upload crafts counts parts wrongly. I counted 60 structural intakes on Jupitec 10, site says 49... Anyway that amounts to 0.015 intake area per engine. Significantly less than Aeris 4. Tell that to whoever asks

Thing with liquid tanks was that you have to have a balanced mix of rocket fuel in orbit. Ratio is 1.2, like divide the amount of oxidiser left in orbit with 1.2 and if the result is more than you have liquid fuel, then you need more LF.

If the craft flips on landing, the parachutes are too low. If parachutes break the craft, then there are too many on one single part. Jupitec 10 has all parachutes just below the command pod. Try putting 2 of them high on the pod itself. The rest slightly lower so that they attach to the fuel tank and not to the battery. Maybe even tweak their deploy attitude so that they dont deploy all at once.

[LitaAlto]

I think the site you are using to upload crafts counts parts wrongly. I counted 60 structural intakes on Jupitec 10, site says 49... Anyway that amounts to 0.015 intake area per engine. Significantly less than Aeris 4. Tell that to whoever asks

Thing with liquid tanks was that you have to have a balanced mix of rocket fuel in orbit. Ratio is 1.2, like divide the amount of oxidiser left in orbit with 1.2 and if the result is more than you have liquid fuel, then you need more LF.

If the craft flips on landing, the parachutes are too low. If parachutes break the craft, then there are too many on one single part. Jupitec 10 has all parachutes just below the command pod. Try putting 2 of them high on the pod itself. The rest slightly lower so that they attach to the fuel tank and not to the battery. Maybe even tweak their deploy attitude so that they dont deploy all at once.

Yeah, GameFramer is in alpha and pretty much all of its stats are off. It's got promise though....

On the Jupitec 7 the chutes are above the command pod. I think the problem is the use of wing strakes--they are causing the ship to flip around at around 30 km up. At least, that's with mostly full tanks. As they didn't flip before, I presume I just need to shift the center of mass by using up fuel.

So I sent it to the Mun, landed, and got a return trajectory--but the game crashed and got weird, and the last quicksave was prior to the Mun transfer. But I'm confident I can land there and return. YAY.

Thank you again for the help!

[Radam]

At 30km up, just when air is running out? Thats probably becouse of asymetric thrust when air is running out.

Read up on intake flow rules here:http://forum.kerbalspaceprogram.com/threads/92752-How-to-exploit-intake-air-flow-logic-for-profit

[LitaAlto]

At 30km up, just when air is running out? Thats probably becouse of asymetric thrust when air is running out.

Read up on intake flow rules here:http://forum.kerbalspaceprogram.com/threads/92752-How-to-exploit-intake-air-flow-logic-for-profit

No, at 30 km DOWN, during re-entry. I'm talking about the chutes.

I'm pointing retrograde during re-entry until about 30 km, at which point the ship flips, and then I'm not able to get out of prograde. The chutes open behind the craft, and when they fully deploy, they tear the ship apart.

This is all new behavior that didn't occur before.

BUT--I strongly suspect that's because the CoM is rather high, given how much fuel I still had on board.

So, I'm testing that theory by flying to the Mun and back. I've already landed, planted one flag, then went scouting for a better (future) landing site. I'll plant a flag there, then return--at which point I should have so little fuel left that the CoM should be close to its final position.

And once I return--I'm taking the strakes off.

[Rune]

No, at 30 km DOWN, during re-entry. I'm talking about the chutes.

I'm pointing retrograde during re-entry until about 30 km, at which point the ship flips, and then I'm not able to get out of prograde. The chutes open behind the craft, and when they fully deploy, they tear the ship apart.

This is all new behavior that didn't occur before.

BUT--I strongly suspect that's because the CoM is rather high, given how much fuel I still had on board.

So, I'm testing that theory by flying to the Mun and back. I've already landed, planted one flag, then went scouting for a better (future) landing site. I'll plant a flag there, then return--at which point I should have so little fuel left that the CoM should be close to its final position.

And once I return--I'm taking the strakes off.

Yup, I think you diagnosed the "lawn dart" issue yourself. You solution will work, at least until the new aerodynamic model comes by. At that point, all bets are off, but certainly having rockets that are as stable going up as going down is going to be trickier.

Rune. Any day now! Aren't you excited about all the ships it'll break?

[Radam]

Any day now! Aren't you excited about all the ships it'll break?

Yeah I am, but I guess rockets wont be that problematic. At least simple ones. Thing is that even using FAR really wide rockets are still not hampered by aerodynamics. In most cases the opposite is true. At least from my experience.

[LitaAlto]

Video of me flying the Jupitec 7-A to the Mun:

I did get back to Kerbin in one piece, too--although it became apparent I had excess oxidizer. That's easy to fix, and I'll probably do so in the next few days.

Edited April 13, 2015 by LitaAlto
Fixed video.