A young impetuous appeals to the ancients wisdom

[XB-70A]

Hi everyone,

First of all please forgive me if I made an error to wrote this thread in this section...

Now here comes the problem. I would like to launch some kind of 'Duna express' flight since two days but every test ended by a complete or (at best) half-failure.

Here are the goals that I have to meet :

- Standard take-off and landing, no vertical launch (from Kerbal and Duna)

- Max crew of 4

- MTOW 80 tons

- One or two turbojets as a gliding assistance when descending back to the KSP

- Payload consisting of a Duna 'jeep' with a 3 tons loaded weight

- No in-space rendez-vous for refueling

- Nothing should remain on Duna, each parts and crew member must return on Kerbin

I firstly choose to use a Mk 3 large cargo bay to place the jeep but my first problem was to 'deliver' it on duna, I chose to reverse the section like a bomb bay and drop the vehicle from here once on Duna ground but without any crane but how to raise and re-hang it on board. Then I found this excellent add (http://forum.kerbalspaceprogram.com/threads/79542-90-SXT-Lack-s-Stock-Extension-SXT-19-07DEC14-KSC-v3?p=1640505&viewfull=1#post1640505) giving a classic loading ramp.

Now here are the problems : lift is insufficient in most of the configurations I tested, controls response is terrible (not that it is bad but over reactive), probably due to great instability. The installation of the J-X4 in lateral nacelles causes high drag while an in-tail dual installation dangerously back the center of gravity, inscreasing the instabillity. And finally the most frustrating, I do not manage to reach the upper layers of the atmosphere ... the speed is still insufficient and thrust with different liquid engines as on-wings solid boosters configuration near always too low to compensate the mass.

Does anyone of you have any ideas or concepts that could meet these requirements?

Thank you in advance.

Edited June 6, 2015 by XB-70A
Answered

[YourEverydayWaffle]

I doubt you can do this is one flight. I currentely have a station in orbit at Duna, and am preparing to send a superstation (weighs at least 800 tons) there, and fuel is a serious issue, and this goes for all flights, really. Also, with the better aerodynamic physics, I think you'll probably be fine as far gliding goes without an engine, but if you really need to, just go with one engine and maybe 600-ish fuel to cut down on weight and size. With a medium sized jet, I've gotten 100+ kilometers range out of that much fuel, and that jet was supersonic, so you might have slightly better efficiency with something subsonic (not sure about that though). I can't give too much help with the other stuff, as I'm more of an plane guy. Although this is still a game, I still highly reccomend doing R&D flights, like flying a section just into orbit, then back to test reentry stuff, or something along these lines. Very, very helpful. Also, you might want to try a super/hypersonic setup for your jets, because it is possible to to keep your supersonic speed all the way down to sea level from reentry, even if your spaceplane isn't capable of breaking the sound barrier in normal flight. If you can stay supersonic, you can also cut WAY back on wing area, and therefore drag and some mass. The JX-4s produce over 1000 thrust at supersonic speeds (mach 3 I think), so that could potentially solve some issues with gliding assistance on reentry. Just my two cents. I feel like supersonic flight is the way to go if you can on the reentry portion of the flight, but that's just me.

By the way, could you post some pictures?

[Mister Dilsby]

You can use the 'bomb bay' approach, just put a docking clamp on a girder in the middle of the rover and dock it to the ceiling of the bay. Kind of similar to this concept:

Drop the rover by undocking, of course. Re-dock it by driving the rover under the clamp, then raising it by any of the following means:

1. VTOL system -- vernor engines work great and auto-balance using RCS controls

2. Deploy landing legs on the rover

3. Lower the mother ship to the rover by pulling up its landing gear.

[capi3101]

Hi everyone,

First of all please forgive me if I made an error to wrote this thread in this section...

Now here comes the problem. I would like to launch some kind of 'Duna express' flight since two days but every test ended by a complete or (at best) half-failure.

Here are the goals that I have to meet :

- Standard take-off and landing, no vertical launch (from Kerbal and Duna)

- Max crew of 4

- MTOW 80 tons

- One or two turbojets as a gliding assistance when descending back to the KSP

- Payload consisting of a Duna 'jeep' with a 3 tons loaded weight

- No in-space rendez-vous for refueling

- Nothing should remain on Duna, each parts and crew member must return on Kerbin

I firstly choose to use a Mk 3 large cargo bay to place the jeep but my first problem was to 'deliver' it on duna, I chose to reverse the section like a bomb bay and drop the vehicle from here once on Duna ground but without any crane but how to raise and re-hang it on board. Then I found this excellent add (http://forum.kerbalspaceprogram.com/threads/79542-90-SXT-Lack-s-Stock-Extension-SXT-19-07DEC14-KSC-v3?p=1640505&viewfull=1#post1640505) giving a classic loading ramp.

Now here are the problems : lift is insufficient in most of the configurations I tested, controls response is terrible (not that it is bad but over reactive), probably due to great instability. The installation of the J-X4 in lateral nacelles causes high drag while an in-tail dual installation dangerously back the center of gravity, inscreasing the instabillity. And finally the most frustrating, I do not manage to reach the upper layers of the atmosphere ... the speed is still insufficient and thrust with different liquid engines as on-wings solid boosters configuration near always too low to compensate the mass.

Does anyone of you have any ideas or concepts that could meet these requirements?

Thank you in advance.

So lemme get this straight - you're wanting a four Kerbal, eighty-tonnes-maximum spaceplane that can fly to Duna, land, drop off and re-load a three tonne rover, then head back to Kerbin for a landing at KSC, all without refueling in space.

That's a damn tall order. A damn tall one. And yet, part of me is sitting here going "challenge accepted"... I'd have to do the math to see if anything of the sort would be possible, of course.

Let me echo the mighty YourEverydayWaffle: can you show us some screenies of what you've got going on so far? The rover design is of particular interest, given its mass. I'm also curious to know which mods you're playing with, if any - the aerodynamic model you're using may prove crucial to your goals - and, if this is your career game, which techs you've unlocked (if it's sandbox, say so).

My initial thought is a three-sequence engine setup - 3 Turbojets, 6 Thuds, 1 Nerv; if you've got RAPIERS, you could change that up to 4 RAPIERs instead of the Turbojets and Thuds. Takeoff and land from Kerbin with the jets, switch to the Thuds when you're in atmo/taking off from Duna, switch to the Nerv for the interplanetary portion of the flight. The tricky bit would be Duna takeoff...there's air on Duna, but not a whole lot, so I wouldn't expect the wings to be of much use. At least your Thuds/RAPIERs would give you sufficient TWR for the job.

4 Kerbals...since you're going to be pressed for mass, I might suggest a command module area consisting of 4 Mk1 Lander Cans in series with a nosecone up front and the rest of the plane in the rear. The mass of 4 Mk1 cans is 2.64 tonnes, a 1.26 tonne savings over a Mk3 Cockpit.

You also say nothing about refueling on Duna...how would you feel about docking your plane up to a refueling rig you've sent down to the planet ahead of time?

Edited June 3, 2015 by capi3101

[Mister Dilsby]

That's a damn tall order. A damn tall one. And yet, part of me is sitting here going "challenge accepted"... I'd have to do the math to see if anything of the sort would be possible, of course.

Oh, I think it definitely can be done. My Hummlebee Mk2 (shameless plug, see comic in sig ) is about 55 tons and meets almost all of these specs. Differences are,

--needs the "Orange Knight" rocket booster plane to lift off from Kerbin

--does not include a rover; simpler for me to taxi around on landing gear or do suborbital hops

--no jets, uses aerospike rockets for gliding assist and a vernor-based VTOL system

And in addition to the listed specs it does have full ISRU gear for self-fueling. OP could certainly add a couple of turbojets if desired (IMO unnecessary) and a 3t rover should not be too much trouble.

[TheXRuler]

If this is not for a challenge then I would reccommend trying something else. If it is, well, definetly use a NERV for all your inspace burns. And learn to use gravity assists if you do not already know how. It should definetly be possible, I have seen people land on duna with the kerbal-X stock rocketso I now firmly believe that anything is possible. If it doesen't absolutely have to be a SSTO you might try adding drop tanks, leaving behind a few tons of empty tank can do wonders for you dV.

- - - Updated - - -

Also, never, ever ever ever EVER EVER EVER use SRB's on a spaceplane (except for leaving the runway) unless you are trying to build something really ridiculous.

spaceplanes are really hard anyway, and ones that can go to duna need a lot of knowledge and experience, or a hella lotta math

[XB-70A]

Thank you all for your advices. There are so many things that I don't know which to begin (!) As he was advised to me, both J-X4 are gone, their drag was too important, without considering the jet fuel mass that had to be embedded (and be a dead weight for the rest of the flight). I managed some minutes ago to launch, orbit the Mun and recover one experimental ship without any losses (pieces as crew members). The trouble is I do not know the procedure for taking screenies. This project is made of a small pack of pieces from around 50 mods, it got a Mk3 cockpit a V-tail, two canards plans, trapezoidal low aspect ratio wings and the main landing gear is partly housed in the four segment Mk3 cargo bay.

Of course this would not be possible without a bit of "cheating"... propulsion is provided thanks to the Impossible Innovations mod from jandcando (http://forum.kerbalspaceprogram.com/threads/86331-0-24-x-Impossible-Innovations-0-5) with two LE Deuterium engines at the wingtip to reach a 210 km Kerbin orbit. Each coupled to one x8 deuterium tank they still have some once above the planet. Two other HE Deuterium engines are installed near the trailing edge of the wings, each with a x2 tank. They provide enough thrust to take-off from the low lunar gravity. I have not yet designed a simple exploration vehicle, and have therefore loaded two tons of batteries to simulate its weight.

Also, never, ever ever ever EVER EVER EVER use SRB's on a spaceplane (except for leaving the runway) unless you are trying to build something really ridiculous.

To be honest this stupid idea originaly came from Ace Combat 5 the Unsung War nostalgia, where we had to defend a mass driver launching site with a lifting body SSTO carrying two SRBs.

[MarvinKitFox]

Here are the goals that I have to meet :

- MTOW 80 tons

Easy

- Payload consisting of a Duna 'jeep' with a 3 tons loaded weight

3 tons asymmetric payload to Duna, check.

Easy enough

- Standard take-off and landing, no vertical launch (from Kerbal

Ok, it must be a spaceplane. No problem.

- No in-space rendez-vous for refueling

Make that a true SSTO and landign and SSTO and back spaceplane.

Difficulty * 12

and Duna)

WHAT!!???

ok, that ups the difficulty by a factor of 65

Duna does not come with runways, and someone also short-changed it on air to fly with.

Horizontal takeoff on duna needs monster wings, or monster speeds.

- Nothing should remain on Duna, each parts and crew member must return on Kerbin

Ah sorry, my mistake. that 65 in the line above should read 1297 difficulty factor

- - - Updated - - -

t and a vernor-based VTOL system

.

for me, a BIG part of the problem is his spec that it must be a "no vertical launch (from Kerbal and Duna)"

So no vtol. He needs to *fly* off Duna

- - - Updated - - -

Of course this would not be possible without a bit of "cheating"... propulsion is provided thanks to the Impossible Innovations mod ...

Ah, your original post neglected to mention that this design is allowed to run on black magic.

May I suggest you save yourself the effort, and use the HyperEdit mod instead?

Edited June 4, 2015 by MarvinKitFox

[Mister Dilsby]

for me, a BIG part of the problem is his spec that it must be a "no vertical launch (from Kerbal and Duna)"

So no vtol. He needs to *fly* off Duna

You're right. See, that sort of thing is what gets engineers in trouble in real life: making assumptions by association. Horizontal launch is often the most efficient profile--not always. Turbojets are often the best way to ascend and descend in Kerbin atmosphere--not always. There is something to be said for aesthetics, of course--even if cheap expendable rockets are the best way to get a certain payload to LKO, flying an SSTO may be cool and awesome enough that you want to do it that way. But there is such a thing as liking one solution so much that you try to make it fit every application. Have seen it many, many times in my RL career (research engineer, power&energy stuff).

[XB-70A]

It's actually a scalled down model, with a 38t max weight. And as you wrote it Kuzzter, this is no more than a challenge to force me the realization and operation of this prototype, so HyperEdit isn't an option. May it will be an idea as "good" as the doktor Porsche use its Tiger P chassis at all costs, perhaps it will be a success as the Skyraider concept.

I take note of all your suggestions to change the design accordingly in case of multiple failures.

[luizopiloto]

you can do this with a 2 stage spaceplane...

[Mister Dilsby]

you can do this with a 2 stage spaceplane...

Confirmed.

[capi3101]

Screenshot procedure - let's hijack the thread for a moment to address that one real quick. Anywhere when you're in the game, hit F1 on your keyboard. That's all you've got to do: the game will automatically take a screenshot and put it in a folder under your main KSP directory (titled, conveniently enough, "screenshots"), saving it as "screenshot(x).png", where x is a number. The game will automatically check for the next available screenshot number so it'll always save screenies in the sequence in which you take them.

Once you've located your screenie in your file system, you can do whatever you like with it within the bounds of your home OS (copy it, delete it, load it into GIMP and draw fake moustaches on Jeb, etc.). The next step from there is to get it up to the forums. Support for images on the forums was one thing that got permanently borked during the Great Coffee Spill of '13, so you'll need put the image on a photo sharing site such as Photobucket or Imgur; I use Imgur my own self. Once it's up there, these sites will usually give you a direct link to the image you want to post. Then it's just a matter of putting the image in between [ img ] and [ /img ] tags (remove the spaces) and it'll pop up after you post. For example [ img ] http://i.imgur.com/vfslOe6.png [ /img ] without the spaces gives you this particular bad idea from a challenge long ago:

I prefer to center my images up, so I also use [ center ] and [ /center ], wrapping those tags around the image information.

So hopefully that's useful information to you. Now back to your regularly scheduled thread about SSTD designs...

[TheXRuler]

Ah well if you use the OP fusion engines this might actually be possible, albeit very diffucult. As others have stated, building something that flies on kerbin AND on duna is hard enough. Building something that flies to duna, lands and takes of horizontally will be incredibly difficult as the larger wing needed on duna will increase your drag on kerbin to a level where it will be near impossible to reach orbit with enough fuel to even get to duna.

However if you insist (and if the fusion engines are efficient enough) I would say land and take of from duna vertically. It should be possible to build something that has a TWR of greater than one on Duna due to the reduced mass (burnt fuel) and the lower gravity. You said VTOL, have you ever tried building a VTOL aircraft? it is incredibly hard (and really inefficient) to balance a plane for VTOL.

Also, Dunas atmosphere is so thing that you do not even need a plane since there is no pressure and no resistance to speak of. The problem will be, since Duna has such a small (and thin) atmosphere that the added drag and weight from the wings will actually barely (if at all) outweigh the gain, and the added mass will substantially impact your dV. If you really want a spaceplane to somewhere I'd recommend Laythe. It even has oxygen so you can use turbojets/rapiers and the atmosphere is much more like kerbins.

[XB-70A]

Thank you to all. Sorry for the delay I remain absent these days and did not have time to answer.

By following the tutorial of capi3101 I've realized that I had taken a lot of capcha without realizing it (probablywhen trying all the buttons at a time), and the first prototype was there. Here it is:

A true crossbreed...

@TheXRuler : my sole VTOL project actually was a Ryan XV-5 like (waiting for a XV-4 like project instead), using in-wings lift fans, so it requires an air density near the "Kerbin standard atmosphere". But as you recommended I think to turn this project to Laythe and leave Duna to the pure rocket-landers design.

I switch this topic as "answered", all your tips will greatly help me (when I have enough time to applied them).

Thanks again.