Fairings + Aircraft parts = booster?

[almagnus1]

So after mucking around with KW Rocketry a while, and staring at while getting a rocket into orbit (late at night), I noticed that the KW Rocketry fairing vaguely reminded me of the nose of an aircraft. Then it hit me:

What if a space launch vehicle used fairings with other flight control surfaces to create a booster stage that used air breathing engines to get the payload out of the atmosphere, then shed the fairings (and the control surfaces), and continued on it's merry way as a rocket?

Theoretically, this should work, and provide an interesting technique to get something to orbit - especially if you could attach the control surfaces (and landing gear) to the fairings, so all it's all staged when you shed the fairings.

I've only started exploring the idea (and only have a very rough vehicle design that's inpsired by the SR-71), and wanted to throw the idea out there.

Thoughts?

Edited December 25, 2013 by almagnus1

[Grover]

um, some images to describe the proposal? why not just use a normal booster, thats always kept jeb happy

[Tex_NL]

Aerial launches can be extremely cost effective.

Get up has high and as fast as you possibly can in airplane mode. Only then shed your fairings and ignite the rocket. Similarly to and airplane SSTO you could call this a TSTO: Two Stage To Orbit.

[Mystique]

The problem will be lack of air for intakes. Using new fancy two-mode engine won't be as much fuel efficient, imho. I'd try to use turbojet stage with lots of ram intakes and amount of fuel just enough to get to upper atmosphere (1 mk1 fuselage per engine may be enough), but it may not be efficient and reliable anyway: jets take time to heat up, when they start turning off because of lack of air their may cause instability of your rocket and they won't be able to get you out of atmoshere (I'm not talking about smaller payloads like satellites, it may be sufficient for them). I'd also start making gravity turn earlier in order to squeeze all what jets can in atmosphere before their fuel runs out, then start quick ascent just before jet fuel is finished, then switch to rocket. And I also think that it won't be price efficient when you'll actually have to pay for parts

P.S. I saw an interplanetary hovercraft on space port that uses jets for takeoff, I guees it may be worth looking at for learning purposes.

[almagnus1]

Thanks for the responses thus far, here's more info:

I'll try to describe the design as best as I can and get into more of what's going wrong shortly. I'm using the mods B9, KW Rocketry, FAR, and DRE. Unfortunately, it will be a couple of days until I'll be at my desktop again (which has the save files), so I'll describe the craft as best as I can. I'm using the vehicle for a Munar mission, with an 1 seater service module + lander, so once it's in orbit, it's fairly similar to an Apollo style mission. I figure that will be a good enough proof of concept that I can use what was learned for other craft later on.

Basically, the craft looks like an up-scaled SR-71, with the engines, their fuel tanks, and air intakes mounted in the wings. The center fuselage has a forward and rear fairing (so it's aerodynamic), with the forward fairing containing the lander and service module, each connected to a set of structural elements via decouplers, and the lander is attached to the fairing base via decoupler. On the outside of the front fairings, canards are mounted, while wings are moutned to the rear fairing. The rear fairing also covers the rocket engine (which is probably not an optimal design decision, but it does allow me to quickly shed the control surfaces with the fairings).

So here's some of the problems I've faced:

* The SPH while really good for space plane construction, and the VAB is really good for rockets, neither are good for a hybrid project of this nature.

* Using assemblies to get parts built in the VAB and then attached to the SPH does interesting things not only with staging, but also gives you Schrodinger's Struts if you also import assembly with the fairing already in place (and canards or wing pieces attached to the fairing). Typically speaking, you will need to restrut the assembly once it's in the SPH - and this is something that I was discovering shortly before I had to shut things down for the weekend.

* SPH symmetry mode does interesting things to fairings, like components mount to the outside and inside of a fairing piece, but not to the other fairing, or at least, from what I recall of working with it.

* Oscillations of the cargo in the fairing in flight, which leads to cargo ultimately swinging through a fairing, which then cause FAR to do nasty things to the structural integrity of the craft.

So yeah, anyone wants to give a crack at it, and see if I'm doing something wrong, or if this is a deceptively hard project, it'd be greatly appreciated.

[Tex_NL]

What you need is Editor Extensions. It allows quick and easy swapping between VAB and SPH symmetry in both VAB and SPH. Click the link to see what else it can do.

[almagnus1]

Oooooh!!!!!!

That's probably half of the problem right there.

I'll have to check back after some more work on the craft.

[almagnus1]

After using the mod, I was able to (start from scratch once again) and actually build the vehicle in a reasonable amount of time....

And a cut away of the front fairing without the wings...

Unfortunately, I'm having an issue where the front fairing, while just fine standing still, keeps coming apart during takeoff causing (rather spectacular) fields of parts down the runway. At least, that's my best guess with what's going on.

Another gotcha I'm running into is the inability to stick a central landing gear on the bottom of the front fairing, and having to go with twin landing gear on the canards. Fortunately I'm not lacking for power, once the engines get spun up, so I'm optimistic that if I can get airborne, this might just work as intended, assuming DRE doesn't eat me.

Edited December 24, 2013 by almagnus1

[Saberus]

As an advocate of stock jet boosters in KSP, I find this relevant to my interests. These designs aren't from mods, they are stock.

http://imgur.com/a/5nSTZ <--This is a link to an old gallery from back before the Great April Forum Kraken Attack. I have built and used these designs in .23, and they still work. The single play is/was lighter than a BACC, and produced 2/3rds the thrust of a BACC, with about 6 times the burn time.

A pair of Triple Play boosters were used on my MEP MK2 and MEP MK3, back before career mode.

http://imgur.com/a/uVbiV <-- Here you can see the math was done on the Triple Play ER vs. BACC's, and the kind of performance you can get from them before even trying to fire up a rocket.

Here you can watch a fellow KSPer take the MEP MK3 to the mun, even with a sub-optimal ascent, and hanging onto dead weight during transfer burns.

If anyone has interest in these designs, I will build them up as sub-assemblies and post them. Fair warning, MechJeb needs serious coaxing and close monitoring in order to make these things work.

[Taki117]

An Idea for your rocket, why not use procedural fairings? Not only can you attach things to them (And they work by using 4x symmetry so you can use 1 forward wheel) but they also use invisible internal struts to keep everything together.

[Markus Reese]

I have actually used the jettisonable wings quite frequently. Whether it is efficient or not now, it is what I use for flying eve. The dense air makes lift crafts seemingly easier to get up the first bit with rocket engines. Probably crazy. I also did this with a space plane lander on duna. I just keep jettisoning wing/engine combo's as I go up until I am out of the worst drag, then boom, full rocket mode.

[almagnus1]

One thing I noticed was the B9 landing gear going squirrelly, which actually took a fair amount of time to figure out as the craft would seemingly randomly yaw, then roll and crash and burn.Once I replaced them with stock gear, the issue went away.

When combined with the strutting I used with the KW fairings (described below) that actually got the craft into the air, and it performed rather well once that happenned =)

An Idea for your rocket, why not use procedural fairings? Not only can you attach things to them (And they work by using 4x symmetry so you can use 1 forward wheel) but they also use invisible internal struts to keep everything together.

That does sound like a good alternative to the KW Fairings. In addition to their size, do they also have mass to them?

That said, now that I've learned how to strut them the Kerbal way, the KW ones are actually fairly stable, but they are missing the attachment points. One trick I learned with them was mounting the fairing pieces to the nose-cone level dots, so I have an exploded view, then strutting those up. When you move them into their proper place, the struts also adjust to attach back to the payload, which greatly improves rigidity.

I have actually used the jettisonable wings quite frequently. Whether it is efficient or not now, it is what I use for flying eve. The dense air makes lift crafts seemingly easier to get up the first bit with rocket engines. Probably crazy. I also did this with a space plane lander on duna. I just keep jettisoning wing/engine combo's as I go up until I am out of the worst drag, then boom, full rocket mode.

How are you mounting the wings and engines so you can drop them?

Edited December 25, 2013 by almagnus1