Single orange tank SSTO to Duna and Laythe

[camacju]

This was for a forum challenge (kind of an orange efficiency reboot) but I thought it merited its own mission report. If I had flown this mission better, I could definitely have included another landing, but I wasn't able to. This mission is at least a good proof of concept however. I don't think anyone else has gone this far with just an orange tank before.

Craft in VAB. Since I can only use the orange tank as fuel, I don't need to use the Big-S wings (although I still could). Instead, I use the standard wing parts. The fairing, tank, intake, and engines are attached, rotated, and offset such that they produce much less  drag. I use minimal rudder surfaces to reduce weight and drag, because I don't really end up using rudder and it's mostly just for stability. Also, the wings are rotated upwards 5 degrees to improve lift:drag ratio while running the lower efficiency nuclear engine in the atmosphere. Finally, I use a single Rapier and a single Nerv as engines. The result is a craft that doesn't look like most high performance SSTO craft but flies pretty well.

The orange tank is drained completely of oxidizer before launch. Neither the Rapier's open cycle nor the Nerv require oxidizer, and I don't use the Rapier's closed cycle at all, since the high efficiency of the Nerv more than makes up for its weight. The closed cycle of the Rapier is only worth it for very light SSTO craft.

I stay near sea level until 400 m/s when I start to climb. I level off at just over 20 km.

At 1600 m/s I turn on the Nerv

In Kerbin orbit with almost 5k delta-v left.

Two periapsis kick burns give me a Mun assist. This transfer was inefficient but not so inefficient that I'd fly it again.

Two Mun assists give me an orbit high above Kerbin where I can loiter until I fly past Mun again.

A third Mun assist ejects me radially where I encounter Kerbin again in one year for another gravity assist.

In the Kerbin encounter, I get another Mun assist to get more energy, since just a Kerbin encounter won't help me any. Using Kepler's third law, I try to get into a sun orbit with the sum of apoapsis and periapsis equal to 3.243 * 10^10, since that represents a 4:3 orbital resonance. This correction burn is very suboptimal but again I've got more than enough fuel.

My calculations were precise enough that I already had the next Kerbin assist plotted.

This raises my orbit up to Duna.

Aerobraking at Duna

Landed at Duna. This was really hard because of the low wing area and thin atmosphere.

Ascent from Duna. My high pitch angle is visible here. Luckily my TWR is above 1 so I can afford to fly at a higher angle of attack until I can pick up speed.

In Duna orbit. I've still got a good amount of fuel left. Can I make it to Laythe?

Ike assist. Again this transfer was likely suboptimal, and I would fly this a different way if I were to do this mission again. Probably by using the same strategy I used for the Kerbin->Duna leg.

I bounce off Kerbin and get a plane change, setting up an Eve encounter. I'm going to do a K-E-K-K-J route rather than something more efficient because the Ike assist gave me extra Kerbin relative velocity.

Eve and Kerbin assists set up

Eve flyby

Tylo assist to capture around Jool and intersect with orbit of Laythe

Descent on Laythe

Aerobraking

Landed on Laythe - much easier than Duna.

Ascent from Laythe, going suborbital on just Rapiers

Laythe orbit. I've got more than enough to get home from here.

Vall and Laythe assists

Tylo assist

Kerbin and Eve assists

Aerobraking at Kerbin

Landed back at KSC