Help needed with space plane designs

[AXCN_K.S.P]

Hi, I've been on KSP since 1.0 launched, and i need some tips on designing a fully functional stock spacecraft that looks Hi-tech and Sci-fi. Some parts i am planning to use are: Advanced Grabbing Unit, Dawn Electric Propulsion System, PPD-12, Toroidal Aerospike, CR-7 Rapier, Airstream Protective Shells, ISRU Converter, Fuel Cell Arrays and Survey Scanners. If you all could post some photos of designs you have made or just give some quick and easy tips would be much appreciated. Secondly, please check the images I've posted on my reply below, as I need help with the aerodynamics of it. Thanks!

Edited June 21, 2015 by AXCN_K.S.P

[AXCN_K.S.P]

Also, i forgot to add that im planning to make it capable of orbiting Kerbin (preferrably a SSTO spacecraft) so it would be great if you could share any ideas on building SSTO's and making them look Hi-Tech/Sci-fi.

[Starhawk]

Hello AXCH_K.S.P, and welcome to the forums!

It's probably best to start with the basics and learn how to make a functional aircraft. This guide is a bit outdated, but an excellent intro to the basic concepts.

I can't imagine what you are going to use the ion engine for in your spaceplane, but then I often can't imagine the things other people build.

Anyway, for some up-to-date info on how people are making spaceplanes, try this thread.

Finally, to get some ideas on esthetics, take a look at this thread or just look around the forums.

Hope this helps.

Happy landings!

[Old Foxboy]

LOL, first of all, you gotta make them work with all the stuff you plan to build into them.

For example: The heavy ISRU converter is a burden for every SSTO. The electric propulsion isn't for spaceplanes though it looks cool. The more "fancy" stuff you add to the plane, the less efficient it will become up to the point where it won't make it to orbit anymore.

So try to approach the SSTO's from a minimalistic point of view.

[Evanitis]

I have the feeling that you aim too high with too little experience. Designing and flying an SSTO is hard enough as it is without extra visual expectations - not to mention that k-ton of payload you are planning to include. Anyways, let me break down the steps towards your goal:

1 - Make a simple, light SSTO that can orbit and land.

2 - Struggle until you actually manage to orbit and land.

3 - Practice filight until you reach a success rate of 20% in orbiting and landing. (I'm currently trying to reach this point BTW)

4 - Repeat step 1-3 with a heavy SSTO loaded with at least a portion of the payload you mentioned.

5 - Pimp the final product until it looks like the way you want it. Realize that it will never reach orbit the way you practiced, so launch it on a conventional rocket instead.

6 - PROFIT!

got ninja'd.

[Grumman]

The Dawn ion drive can provide a lot of delta-V for very little mass, but only if time is not a factor. It's no good for circularising on ascent, but if you want a mass-efficient way of rendezvousing with a space station or deorbiting your spaceplane, an ion drive can do it.

[AXCN_K.S.P]

Thanks to everyone who replied, I've decided that I'll probably work on more simple SSTOs for the moment. Anyways to my second question, I was wondering how i could improve my SR-71 that i am currently working on, i'm trying to get the craft to LKO but it seems to struggling getting lift unless i use RCS to angle the Plane. Any ideas what could be done to the ship to increase lift without making the ship look completely different and yet still function like the real one? Thanks.

Here are the images:

[*Aqua*]

What's up with all the SAS? Remove them and add a monopropellant tank and some RCS thrusters. You'll also need solar panels or an RTG or it'll quickly run dry in space.

If you don't have enough lift you either don't have enough wings (they add drag!) or aren't fast enough (not enough engine [power]).

Edited June 21, 2015 by *Aqua*

[rofltehcat]

How heavy is it, how much fuel and oxidizer does it carry? Can you also make a screenshot with centre of lift and centre of mass? At first look it seems to not carry enough oxidizer and maybe to be a bit too heavy for the two engines.

[AXCN_K.S.P]

Thanks for the tips, I've now re-designed the Blackbird and added those parts that you both have mentioned. The Resource capacity is: 2150 Electric Charge, 415 Mono Propellant, 1900 Liquid Fuel, 880 Oxidizer. Changes: Now uses the CR-7 RAPIER Engines, Has Vernor and RCS Blocks for RCS, Added Batteries (offset inside the plane so it isn't seen), Added more Oxidizer and Mono Propellant and re-fitted fuel lines. Here are the pictures:

[Old Foxboy]

did you actually build the rapiers + turbojets in line behind each other?

Remove a lot of fuel (click on the tanks and drag down on the sliders to balance weight + centre of mass.

Use Turbojets only, not rapiers. A SR-71 can't go to orbit in real life.

[CalculusWarrior]

I disagree with Old Foxboy; if you want to make an orbit-capable SR-71, go for it! That's the great thing about KSP, you can make whatever you want fly! However, there's no need to jettison the turbojets, you should be able to fly on the atmospheric mode of the RAPIERs alone; you don't need the jets.

As for spaceplane design, you generally want the centre of lift to be behind the centre of mass, this makes for a far more stable plane. Those giant landing gear are likely adding quite a bit of mass; you can probably make do with the smaller ones.

The thing about spaceplanes is that after a certain point, plane design becomes irrelevant; it's all in how the plane is flown. What issues are you experiencing now?

[Kagame]

Looks like you don't have enough vertical control authority. Try replacing those teeny little Elevon 1s with some Elevons 2 and/or 3. As a last resort, offset some Basic Canards into the fuselage body.

[Capt. Hunt]

I would ditch the turbojets, the RAPIERS aren't as efficient but they'll do the job in atmo, carrying both sets is just going to add weight and offset the extra efficiency of the jets. What's with the cubic-octostrut above the nose gear? That's also going to add weight and drag that you don't need. I would replace that with another large landing gear, like the two you are using for mains. When designing rockets or spaceplanes, you need to look beyond the aesthetics, what works for Lockheed Martin Skunkworks in real life might not work for you in KSP.

[AXCN_K.S.P]

Ok thanks everyone, being a bit new to KSP means i'm not very experienced with construction of large-scale aircraft, but the help given by all of you should help me for future reference, once i perfect this design making it into a working SSTO (Hopefully) i'll probably go and post it on the Spacecraft Exchange.

[Mic_n]

I tend to agree with what's been said.. If you're going for SR71 style then you've got two engine pods to work with.. so either rapiers (don't add the turbojets inline behind them.. it's weight you probably don't need and on the technicality - that's not an SSTO) or turbojets with perhaps aerospikes clipped in on top of them, which is kinda cheat-y but if you're going for visuals works pretty well.

But the thing is, with those two engine pods, you look way too heavy. You're just not going to be able to push that much fuel up to the 900-1000m/sec you want to be hitting before you start burning oxidiser. Empty some of those tanks or switch them for cargo bays and have something you can use as a shuttle to deploy probes/etc from. The liquid fuel in your engine pods there (what's that, a precooler and mk1 LF?) should do you for your atmospheric flight, and you probably ought to be able to get your rocket thrust from a single one long Mk2 LF+O tanks (with the mk2-mk1 adapter at the tail there as well). It can be a bit surprising just how much 'less is more' can achieve.

Your vertical stabilisers there are a little awkward.. From the looks of it they're right there at your CoM and CoL and are likely going to be of limited usefulness.. they should be trailing your CoM to add a little drag at the rear to keep your nose pointed straight ahead. Personally I'd get rid of the "pairing up" of them like you have and try to get them a little more to the rear. (That probably goes for your entire wing assembly, actually.) Also make sure you right-click them in the SPH to set the control surfaces to yaw only - particularly with them being off-vertical like that the system will likely try to use them for roll and pitch control as well.

Also.. yup, bigger control surfaces will help with your pitch control (take a look at a diagram form of the SR-71 - those elevons really are huge).. vernor engines and RCS is not something you should be mucking with. If you want, you could also use the small rectangular wing sections and strakes to extend your wingform up the sides of the main body toward the nose, and tuck some little elevons up the front there to act like canards.

Alternately, you could continue the SR-71 theme and use fuel control to shift your CoM around. Either disable fuel flow on your rearmost tanks from launch or alt-right click a pair of tanks to transfer fuel in-flight to make it a bit more tail-heavy and help get your nose up... be very careful there though.. too much will make you flip uncontrollably.

[GoSlash27]

I concur with the earlier responses. SSTO spaceplanes have a narrow window of success after KSP 1.0. You have to learn how to make a functional spaceplane before you start trading off practicality for cool looks.

Good luck!

-Slashy

[Old Foxboy]

Just another tip: You can tilt the wings a little (!) bit to create a lot of extra lift while keeping the rest of the craft with a low AOA in the airstream. That's what they do in real life, too. Use the rotation tool and press shift to make a very small increment.

[Mic_n]

A SR-71 can't go to orbit in real life.

FWIW, SR-71 reached around 26km altitude and over 3500m/s.. which is in itself a pretty damn high suborbital hop in Kerbin.. the circularisation burn you'd need at an Ap that high to raise your Pe a mere 50km would be easily achievable with minimal rocket power.

Yeah, direct translation in a scaled-down universe, but hey.. It's the most sci-fi damn plane that ever existed, so let people sci-fi it up!

[Old Foxboy]

FWIW, SR-71 reached around 26km altitude and over 3500m/s.. which is in itself a pretty damn high suborbital hop in Kerbin.. the circularisation burn you'd need at an Ap that high to raise your Pe a mere 50km would be easily achievable with minimal rocket power.

Yeah, direct translation in a scaled-down universe, but hey.. It's the most sci-fi damn plane that ever existed, so let people sci-fi it up!

Nope, the SR-71 never reached this speed. You confused km/h with m/s. Divide your number by 3,6 and you are at about 1000 m/s, which is the Mach 3,x - the speed a SR-71 can fly. And it's pretty much the same performance you get from the Turbo-Ramjets in KSP. A SR-71 never could make it to orbit. Not on Earth, and not even on Kerbin.

[Mic_n]

bloops. You're absolutely right. I'm well aware the ~mach 3.5 and 85k ft altitude figures. Brain not working so well at the end of the day, I put it down to Still. Sci-Fi it up!