How to piggy back?

[7499275]

We've all seen the picture of the space shuttle ridding on the back on a 747. We've all seen pictures of the X-37 under a B-52. I want to do this.

Essentially create a plane (ex. 747) And be able to attach a smaller more nimble plane to the top or bottom. Top would be easier though due to ground clearance with low gear. Why? Well I can make a space plane. However it usually does not have a whole lot of fuel left afterwards. Not enough to carry its cargo to its destination. What I am trying to do is use this large (747) to carry this small craft into the higher parts of the atmosphere. (30-35km) at which point it would detach and fire into orbit on its own fuel at that point.

Another concern I have is... I don't want to loose both planes. If I were to control the smaller craft once the 747 got past 2.2km it would vanish and I would be out probably a couple ten thousand dollars. I could use stage recovery but that wouldn't work well as it wouldn't give me a 100% refund because it would be many kilometers away from the KSC when if I were to pilot it, it could fly back to the runway and get a 100% return value.

Any help would be appreciated guys.

[Newnard]

I have no advice for the construction half of the question, as I'm bad at spaceplanes in general.

For the recovery of both parts to work, you need to fly a steep enough trajectory to put BOTH vehicles above the atmosphere long enough that you can circularize the smaller one's orbit, then switch back to controlling the bigger one before it re-enters the atmosphere to guide it down. I've done this with rocket stages, just never with a plane setup.

[Tex_NL]

Can't remember the name, but there is a mod that allows you to make a small step back in time to the moment your planes separated enabling you to land the second plane safely after you've flown the first to orbit.

[7499275]

Can't remember the name, but there is a mod that allows you to make a small step back in time to the moment your planes separated enabling you to land the second plane safely after you've flown the first to orbit.

I'll have to look for that! that sounds like it would be perfect.

[The Yellow Dart]

Sorry that this doesn't answer your piggy back question, but just as a thought, have you considered a Dreamchaser-style approach? If you are having trouble with an SSTO spaceplane this is a good alternative that requires a lot less design skill and effort to build and still allows good recovery rates if you build the booster with SRB's and can get the plane near KSC. If you want full recovery/reusability you could make a large single first stage capable of putting your craft on a high suborbital trajectory, then circularize the small craft ASAP and go back to the booster before it goes below 20,000m and recover with parachutes off shore from KSC. OR for even more challenge, try to make a "fly-back" booster that can fly or glide back and land on the runway after separation.

[Claw]

Here's one example. I made this a few versions ago, but the idea should still work fairly well.

Without payload, the CoM is a bit low (on purpose). Once you put the payload on, the CoM is a little high. So I designed the plane to be able to handle having the CoM slightly high or low. One the fuel is drained out of the carrier, the CoM is just about in-line with the CoT.

You can fly this up high enough that the smaller plane is released well above 22km. This allows enough time to put the small plane into a high enough orbit that you can switch back to the carrier and fly it down.

Cheers,

~Claw

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Edited November 27, 2014 by Claw

[worir4]

Wouldn't it be great if we had like a sort of timer device. For example parachutes deploy 5 seconds after activated. Then you wouldn't have to worry about landing the plane.

[Darkstar One]

Wouldn't it be great if we had like a sort of timer device. For example parachutes deploy 5 seconds after activated. Then you wouldn't have to worry about landing the plane.

Uhm, they exist already: http://forum.kerbalspaceprogram.com/threads/64227-0-25-Smart-Parts-V2-0-3-KSP-25-Compatibility-Nov-3

[Claw]

You'd still have to watch the plane come back down with timed parts. If you want your money back without flying it (or following it down), try debrefund.

[7499275]

Here's one example. I made this a few versions ago, but the idea should still work fairly well.

Without payload, the CoM is a bit low (on purpose). Once you put the payload on, the CoM is a little high. So I designed the plane to be able to handle having the CoM slightly high or low. One the fuel is drained out of the carrier, the CoM is just about in-line with the CoT.

You can fly this up high enough that the smaller plane is released well above 22km. This allows enough time to put the small plane into a high enough orbit that you can switch back to the carrier and fly it down.

Cheers,

~Claw

http://imgur.com/a/mpA63

This is exactly what I want to do. Just on a much larger scale which is easier said than done...

[LABHOUSE]

Wouldn't it be great if we had like a sort of timer device. For example parachutes deploy 5 seconds after activated. Then you wouldn't have to worry about landing the plane.

You could just adjust the minimum atmosphere pressure.

[-ELF-]

Step 1: Find yourself a second pilot.

Step 2: Install DarkMultiPlayer mod. Both of you.

Step 3: Choose your vehicles.

Step 4: After separation he controls the mother...plane and you control the Orbital plane, or vice versa.

Step 5: One plane is in orbit, another is recovered

Step 6: Profit!

[Axelord FTW]

I just leave it to StageRecovery to deal with the lifter craft.

[RainDreamer]

You can try this: http://forum.kerbalspaceprogram.com/threads/48720-TT-NeverUnload-Vessel-Unloading-Preventer

I never used it, so I can't say how well it will work, but it might help if you want to control multiple vessels.

[pvtnum11]

I tinkered with this all morning. Problems manifested in the CG shifting as the plane's fuel is expended while it ascends. But it did work (for a loose definition of "work"), provided I didn't care about having the now-abandoned plane disappear once it left the 2.4km physics radius of the rocket I was controlling. As a technology demonstrator, I rate it a paltry 6/10, since the plane is a total writeoff. I was playing mostly stock (I have only RPM on my Steam install).

There are mods that address this, though, so all is not lost.

Maybe we'll have better luck with the concept once the Beta 0.90 Mark 3 parts hit the street. They're pretty beefy.

[7499275]

I think its funny. I appreciate all the replies and help but you all seem to focus on the unloading issue, that was honestly the least of my worries lol.

[m4rt14n]

I did an exercise on this idea a while back...

You'd need some kind of autopilot(mechjeb) to hold the plane steady while pushing the payload plane into orbit.

http://forum.kerbalspaceprogram.com/threads/68179-Spaceship-One-Delivery-(Spaceplane)

The biggest problem is wobbling, center of mass shifting after payload seperation and mass shifting due to fuel losses (because it is a very big heavy plane)

Edited November 28, 2014 by m4rt14n

[The Yellow Dart]

I think its funny. I appreciate all the replies and help but you all seem to focus on the unloading issue, that was honestly the least of my worries lol.

Well, that was the only problem that can really be addressed without writing a page of text on building planes. There are one or two tips people could give you for "piggy backing" but for the most part it is essentially the same as building 2 regular planes. Put your center of mass in front of center of lift, gain as much speed as possible on jets before switching to rockets, or in this case before decoupling your rocket spaceplane.

[pvtnum11]

I think its funny. I appreciate all the replies and help but you all seem to focus on the unloading issue, that was honestly the least of my worries lol.

Negative. The CG shifting issue manifested before I even got to unloading the rocket - indeed, that's what caused me to unload the rocket in the first place, in an effort to save something, as the all-up assembly lost all flight control due to a loss of stability. After I did that, it was pretty simple. If you can manage to keep the all-up assembly under control during the ascent, that's a big plus. The rest is easy.

[MarvinKitFox]

Another concern I have is... I don't want to loose both planes. If I were to control the smaller craft once the 747 got past 2.2km it would vanish

Some thoughts and corrections:

* The carrier plane would only vanish when past 2.2 km, if it goes below about 24km altitude.

What it *will* do though is go pure ballistic, i.e. no lift!

With a carrier "plane" this is a problem, as you are dependent on the wings' lift to keep you up.

My approach to this is to rather use a ballistic launching stage, somewhat like the Falcon9 approach.

Have the payload vehiocle mounted on the nose of the launcher.

Launch ballistic, in a high arc with Apo somewhere in the 70-90km .

After seperation, retroburn HARD to send your launcher back to runway, on a slow arc that will take 3 min++ to enter atmosphere.

Only now burn your orbital unit to orbital velocity.

if you insist on using a winged lifter, and you a re using a recovery mod, consider flying to the west first, then turnaround to easterly launch direction, and launch the payload vessel when you are crossing over KSC again. As your lifter is likely jet-powered, it has the fuel efficiency to manage this.

As for design:

The x15-under-wing approach works fine, but only if the carrier outmasses the payload by MANY to one. Otherwise you end up with some gnarly off-balance torques.

If the orbital vehicle is small enough, you could try the Pegasus-under-TriStar approach. Ground clearance tends to be an issue.

Shuttle-on-747 looks the best, but flies like carp. The off-center drag and lift is very problematic, and shedding an inert load *above* you is dangerous.

Spaceshiptwo-under-WhiteKnightTwo looks good too, and flies nicely. You do need to master twin-boom lifter design first, of course. Dropping the inert payload is easy, as long as it has less wing-lift than your carrier.

Personally, i prefer the x37-on-AtlasV approach.

Simple tech, symmetrical load, neatly packaged in a payload shroud. The only real challenge is the timing of a ballistic quick return.

I usually chicken out, and beef up the launcher a lot, so that it becomes an almost-orbital vehicle that flies once around the planet before landing.

[7499275]

Some thoughts and corrections:

* The carrier plane would only vanish when past 2.2 km, if it goes below about 24km altitude.

What it *will* do though is go pure ballistic, i.e. no lift!

With a carrier "plane" this is a problem, as you are dependent on the wings' lift to keep you up.

My approach to this is to rather use a ballistic launching stage, somewhat like the Falcon9 approach.

Have the payload vehiocle mounted on the nose of the launcher.

Launch ballistic, in a high arc with Apo somewhere in the 70-90km .

After seperation, retroburn HARD to send your launcher back to runway, on a slow arc that will take 3 min++ to enter atmosphere.

Only now burn your orbital unit to orbital velocity.

if you insist on using a winged lifter, and you a re using a recovery mod, consider flying to the west first, then turnaround to easterly launch direction, and launch the payload vessel when you are crossing over KSC again. As your lifter is likely jet-powered, it has the fuel efficiency to manage this.

As for design:

The x15-under-wing approach works fine, but only if the carrier outmasses the payload by MANY to one. Otherwise you end up with some gnarly off-balance torques.

If the orbital vehicle is small enough, you could try the Pegasus-under-TriStar approach. Ground clearance tends to be an issue.

Shuttle-on-747 looks the best, but flies like carp. The off-center drag and lift is very problematic, and shedding an inert load *above* you is dangerous.

Spaceshiptwo-under-WhiteKnightTwo looks good too, and flies nicely. You do need to master twin-boom lifter design first, of course. Dropping the inert payload is easy, as long as it has less wing-lift than your carrier.

Personally, i prefer the x37-on-AtlasV approach.

Simple tech, symmetrical load, neatly packaged in a payload shroud. The only real challenge is the timing of a ballistic quick return.

I usually chicken out, and beef up the launcher a lot, so that it becomes an almost-orbital vehicle that flies once around the planet before landing.

Wow! Okay, The B-52 is a possibility provided I can get the counter balance right. Also the space ship two the twin boom looks promising! Thank you. This gives me ideas to play and work with!