Athena SSTO - Getting large payloads to orbit in style

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Athena SSTO

The Athena is the logical extension of the Minerva. It uses essentially the same airframe, but stores liquid fuel and oxidizer in most of its tankage instead of just liquid fuel, and 4 OPT ARIE engines are added, along with 4 extra air intakes. Instead of the APUs that the Minerva used, stock Fuel Cells and RTGs provide constant charge to the batteries.

The Advanced Turbo Ramjets will get the Athena from the runway up to around 10,000 meters easily. From there, give the Athena a kick from the OPT engines until your speed is about Mach 1.6. That crosses the power threshold for the ramjet function. You can then turn the ARIE engines off again and let the jets continue to take you up to around 20,000+ meters. Keep gaining speed and altitude as long as possible, then kick up to 25-30 degree angle and activate all engines again before leveling out to follow pro-grade.

If you manage your climb to orbit just right, you’ll be left with about 30-40% fuel remaining after circularization, depending on the load you’re lifting.

Also note - during the ascent you may want to turn off the pitch control on the canards at some point to reduce up and down oscillation - this is mainly if you are using MechJeb. If you just have standard SAS on and flying manually, you probably won’t need to do this. And in fact, this SSTO is very responsive to control input despite the large size. (13 reaction wheels will do that for you!)

Vernor Engines provide RCS control, but I recommend only turning them on when needed, as they do consume the main fuel supply. Also - in the version of this design posted, there is no foreward/aft translation control via RCS. So I recommend either not docking to a large station with the Athena as currently designed, or use a small RCS orbiting tug to assist in docking. Or - go ahead and add some fore and aft RCS control yourself. The cockpit module has enough Monopropellent to support limited operations with standard RCS. Or you could install some small Monopropellant tanks in the cargo hold. I tried to keep this design as simple and open to user options as possible. There’s plenty of slack in the design for customization.

I do recommend KAS/KIS for cargo stabilization and/or IR Robotics for positioning docking ports for link-up. But again - I kept those out of the upload so you can design your own solutions. You might even consider adding some engines for VTOL on low-grav landing, since this design is more than capable of reaching the Mun or Minmus. But again - I wanted to keep the download as simple as possible. It's already 111 parts as it is!

Download is available at Kerbal X.