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Spaceship One Delivery (Spaceplane)


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Has anyone ever successfully delivered an attached space plane on top of another space plane? I'm trying to fly into sub-orbit, deploy the payload plane then return to KSC. But whenever the ship(or ships) hits 9000-10,000 m it goes into an uncontrolled backspin. I tested the deliverer plane beforehand and it was able to go to orbit without a hitch. Not sure what I'm doing wrong here...

screenshot21.png

Here's the craft file:

https://dl.dropboxusercontent.com/u/51811839/Flying%20Swan%20Delivery%20Spaceship%20K-One.craft

Edited by m4rt14n
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It is pitching up for a couple of reasons...

1) The mass of the craft on top will lift the center of mass (CoM) upward, above the center of thrust (CoT) of the 4 RAPIERs on the lifting craft. That is the main reason.

2) Minor contribution will be the additional drag of the craft on top.

The reason you don't notice it until you reach altitude, is because the control surfaces are strong enough to keep it flying right in the thicker atmo.

In order to fix it you will need to balance it and/or add more torque. So, some options...

1) Lower the craft that goes to orbit (having it in-line with the lifting craft is ideal)

2) Have the spike on the orbit craft run during ascent with partial thrust (however you will probably get some shifting fuel balance issues)

3) Add more reaction wheels

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Aside from balance, there may be a couple of other tweaks that could improve this design's performance. What altitude and speed is the carrier aircraft supposed to reach before releasing the payload, and where is the payload expected to go? It's possible that you can switch the RAPIERs for turbojets and save a bit of weight.

The payload has 4 tons of fuel and its mass looks like about 8 tons, so with the aerospike it has a vacuum dV of about 2650 m/s and a TWR over 2. I can usually circularize from a TWR of 1 without trouble, and I know people do it with nukes and ion engines (although that's with heavily airhogged designs). Switching the spike for two LVT-909s would get you 3070 m/s (although it might be harder to make that look good), and save 0.75 tons. Three 48-7Ss would get you 3240 m/s and save 1.4 tons. Switching the fuel tank for an FL-T400 and the engine for a nuke gets you about 3000 m/s and a TWR of JUST under 1.

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Martian, that looks pretty sweet. I downloaded it and messed with it a little. I've done carriers before, but they were usually like hang gliders (similar to the White Knight and Space Ship One).

Anyway, your Center of Thrust (CoT) is too low compared to your CoM. When you're designing in the SPH, make sure you set the thrust limit on the aerospike to zero. That will give you the true position of the thrust vector when using the RAPIERS.

Now that you've done that, there's a few things you can do to align your CoT with your CoM. Here are a couple things I tried and it flew better as a carrier, but I didn't test the changes to the carrier after release.

-I moved the carrier's wings up slightly, then bend them back to level. This brought the CoT up some.

-I bent the outboard wings up some and moved the outboard RAPIERS out onto the outer wings. This moved the CoT up a bit more. This also caused me to have to move the aileron. So I replaced the big one with two small ones and put them on the inboard wing.

-I removed the ASAS and replaced it with two inline reaction wheels.

-I replaced the pylon with a TT-38K decoupler to get the plane closer to the carrier. This lowered the CoM a little.

This all helped it fly a bit better. I anticipate that the carrier should still be able to fly okay on the inboard RAPIERS (disable the outboards) after release so that it can fly home.

You could also try to add some external tanks tucked up to the underside of the carrier to move the CoM down.

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Thanks for all the replies. I was looking for a ceiling of 20kms before delivery. Higher than that would be preferable, but not necessary. The idea is to deploy the payload and return to KSC, while the smaller craft goes into orbit and hopefully deorbit back to KSC.

@Claw: If I mess around with the CoT, CoM and Lift would the spaceplane itself be screwy after delivering its payload? Perhaps a glider type is a better deployment vehicle. Rutan got it right lol..

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That looks similar to what I'v done in the past, probably because I also copied White Knight. :P

Now that I have more practice, you made me interested in making a new piggy back design. I did one last night.

Takeoff TWR 0.68

Takeoff Weight with Piggy Back loaded (minus landing gear) 16.8t

Piggy Back Plane Weight around 6.5t with 3500ish dV

It can climb and release above 30km. The carrier is capable of reaching space on it's own too.

I'll post a picture later if you're interested. It was inspired by your design and question. :)

And yes, doing those things I suggested will make the carrier a little messy after release. But I found a nice happy place for the CoT between the carrier's loaded and unloaded CoM. So it wants to pitch up a little when loaded, and down a little when unloaded. So I designed the flight controls to handle that.

BTW: Your most recent White Knight looks better than mine ever did. haha Nice Job. :D

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