Edax

It's my plan to have the Diablous X take off Duna horizontally, assisted by two twitch engines. Are horizontal takeoffs viable on Duna? (I've only done that successfully on the Mun and Minmus with "puff" engines, since they had low gravity). Duna has atmosphere so maybe the wing controls will be enough to get the nose in the air?

Those jet engines are for returning to KSC. The first spaceplane, I call Valkyria III (which has the LV-N) has 3939 Delta V with a full tank, and has already landed on the mun and Minmus several times and returned home. The second spaceplane, the Diabolus X has 2507 Delta V with the toroidal aerospike and is meant for Duna (is that enough Delta V to land and return?) Admittedly the jet engines are a bit of dead weight, but it is an SSTO that docked to the Carrier under it's own power and I only plan to reuse them for reentry. The spaceplanes both can function as escape pods, and I regularly dock mk1 pods with heatshields to transfer crew between the ground and the carrier. I also have no idea how to calculate TWR. I should also note that I'm trying to land on every planet and moon with spaceplanes, so that's a personal challenge I set for myself. - - - Updated - - - Good point, I forgot to pack probes onto the ship.

I'm about to attempt my first mission to Duna, and I've built a Spaceplane Carrier to get my spaceplanes to Duna and Ike to collect science. Since I've never attempted anything like this before, I was wonder if there's any oversights or flaws in this Spaceplane Carrier that could doom the mission, any thoughts? The front end of the ship (the orange tank with the mailsail engine) will be left behind as a refueling station for Kerbin, while the back two-thirds will head off to Duna powered by a Poodle engine. One spaceplane is for Duna, and the other Ike, and this will be a two-kerbal mission. The flight plan is essentially to launch at the prime launch window for Duna, put in an orbit, have Valentina fly the spaceplanes one at a time, gather rocks and data, return to the vessel. After the missions are complete, she will then fly back to Kerbin in the Spaceplane with the LV-N while Jagie will say behind and conduct research in the on-board laboratory. (Remember, I've never left Kerbin's gravity well, so I'm not entirely sure what to expect) Edit: The results of my trip:

It wasn't their ISP in atmosphere I was referring too, it was their low thrust. Very heavy engine with low thrust is a bad combo when trying to get off planets. This is why people use solid fuel when taking off, they have completely horrid ISP, but a good twr, which is specifically need when taking off a planet and countering gravity.

Since LV-N's are useless in atmosphere, I think it'll depend on whether you want to stop by Ike. The LV-N will save you a lot of gas in non-atmosphere landings, but if the mission is solely for Duna, they'll be dead weight. That is unless you plan to leave them in orbit for the landing.

The advantage of the LV-N with spaceplanes with a LF only design, is that when you reenter Kerbal, you don't have to deal with dead-weight oxidizer, all of the remaining fuel can be used to safely put you back at KSC. Another thing to negate the bad TWR is to have a small spaceplane that is capable of refueling in orbit, that keeps the weight low, and the DeltaV and fuel efficiency high, and you only ever have to deal with one fuel gauge.

Wont having low thrust on a heavy object in space make it far more difficult to accurately use maneuver nodes? Thrusting too long after the node could cause dramatic drift and cause orbital insertion burns to cause eccentric orbits thus wasting fuel, right?

I'm unsure if my Mothership SSTO quite qualifies for the K-Prize. Furiosa VI takes off into orbit carrying another Spaceplane, the Valkyria III (with 400 units of Liquid Fuel on board, and a detachable nose cone). In LKO, Valkyria III is detached to rendezvous with my spacestation to fuel up and plant a flag on Minmus to pay the bills while Furiosa VI lands back at KSC. When Jeb is done with his mission, Valkyria III also lands back at KSC. However, the side effect is that the detachable nose cone is left behind in orbit, making this SSTO Mothership/Parasite Spaceplane combo only 99.5% efficient. (Though the nose cone is part of the payload, and not of the mothership) Takeoff Valkyria III's engine is engaged. Top Speed with payload. LKO Jeb is off to Minmus! Who needs landing lights anyway? Fuel situation critical. With 10 seconds of fuel left, Mory guns it. Landed, nothing but tarmac, and 14.92 units of fuel left. Valentina would approve.

Yep, sticking some tail fins behind my Spaceplane has done wonders for control. I'm now no longer have to fly a deathtrap to get my ships into space.

I've noticed that the tail wings are close to the CoM when drained of fuel, even though their already at the back of the plane. Is that the sole cause of the flatspining? Maybe I could stick the tail wings on rear struts?

I don't think it's asymmetric flame-out issue, you'd hear a flameout noise and the engines would spark. I have a ram intake for every turbojet engine. Maybe the air is entering unevenly? The cartwheeling happens pretty much at any low to middle altitude. I usually run an airworthiness test with the payload detached, and the fuel in the back drained so that the center of mass is slightly ahead of the center of lift (this also simulates reentry where I pump all the fuel forward). It's during these tests that I keep cartwheeling. I suppose I can move the tail fins further back, but because there's a slope on the surface area of the plane, would having the tail fins at a 20 degree angle would cause stability issues? Would it be better if I posted a video of the cartwheeling?

The Spaneplane is now more stable and capable of small left-right inputs, but it still cartwheels horizontally. The primary problem I found was the forward T-800 fuel tanks, when I removed them, became more stable. I add 4 more tail fins and a Elevon 1 on the wing (and have them only control yaw, the horizontal Elevons now only control pitch and roll, now when the plane cartwheels, it's mostly recoverable, but I still don't understand why the plane keeps spinning horizontally from medium left-right rudder inputs. FYI it mostly spins out of control when mostly empty of fuel, and payload detached. When heavy, the controls are sluggish and difficult to keep steady unless I'm moving straight or pitching.

Ah, okay.

I stuck a small passive radiator as close as possible to my LV-N, and it has overheated far less then it normally would have in 1.0.2. I'm not sure if placing it near the LV-N helps in any way, but in my eyes, why take the chance?

I suppose I should mention that I used to have 4 tail fins on this Spaceplane, but I removed 2 of them because they were unable to correct an uncontrolled spin, so I viewed them as dead weight (though removing them may have made the problem worse, I just don't know. Back when it had 4, it was capable of making minor turns before spinning uncontrollably.) It was my experience that putting on vertical stabilizers too far from the center would cause all the turns to roll the plane (though I had yaw enabled, so that could have been the problem). So that answer is more vertical stabilizers with yaw disabled?

I've been using this SSTO mothership to get my parasite spaceplane into orbit, but recently, they've lost the ability to make any kind of turns without spinning out of control and forcing an emergency landing. This used to be a stable SSTO until the ever-heavier payload attached to the front forced me to add more wings at the back. It was only recently this instability happened, and I don't know if it's a design flaw involving aerodynamics, game mechanics, or the new 1.0.3 areo model involved, or the fact that the MK1 LF fuel tanks are now way heavier, but if anyone can give me advice, I'd appreciate it.