SSTO Evolution Continues

[Athos]

Hello again, everyone! It's taken me a little longer than expected to get back to building and posting due to a family emergency, but now that that's all resolved, here I am. I've been working on my SSTO designs some more, so I'm back with three further refined versions of craft I posted in my first thread (which have also gotten some minor updates). If someone else hasn't laid exclusive claim to the name, I think I might just label these Evolution Series.

As usual, better results than mine could be achieved with better piloting (or MechJeb). Please fly these and let me know what you think!

Hornet-B is a light SSTO with twin RAPIER engines. The original Hornet was just too difficult for me to achieve orbit under manual control with three engines. Also, Hornet-B doubles the most useful science equipment, allowing for more science per mission.

Her ascent profile is simple; activate SAS, close most of the intakes with group 1, full throttle, stage for takeoff. Gear up and 50 degree AOA, watch intake air and reopen intakes with group 1. Zero AOA at 20km and continue accelerating as vertical speed bleeds off, pitch up slightly as rate of climb approaches zero to maintain slow climb, then pitch back up to 45 degree AOA once you've hit orbital velocity (or when the engine switches modes, if you rose a little too fast). Group 2 toggles all intakes to reduce drag once engine mode switches. Raise apoapsis and circularize. Group 0 toggles docking port.

Her descent profile is even simpler; deorbit to a 40km periapsis, open your intakes with group 2, switch the engine back to air-breathing with group 3, and fly home. For airbrakes, use group 1.

Download

Orbital Delivery Vehicle 1 (ODV-1) is derived from FDV-2B, has been updated with dedicated jet fuel tanks instead of structural fuselages, and has an additional pair of quad intake groups, allowing her to deliver ~2150 fuel, ~2600 ox, 750 monoprop and 4 kerbals to ~100km orbit, with pilot and reserve FL-T800 to bring her home; a significant improvement upon her predecessor.

Ascent: Before takeoff, activate SAS and resource display, throttle up to max, close two intake groups with action groups 1 and 2.

Spacebar to get the party started. Rotate just after passing the VAB. Careful--it's easy to pitch up too fast and start tumbling. After liftoff, gear up and 50 degrees AOA. Open intake group 1 at 13km, and group 2 at 17km.

Zero your AOA at 20km. SAS on its own should keep you stable through the rest of your ascent. The ship will continue to rise while you accelerate. As your rate of climb approaches zero, pitch up to 15 degrees to maintain slow climb. Try to reach at least 1700 m/s before passing through 30km, maintaining max throttle. Faster is better. You will notice some wobble as your engines start to flame out, but SAS will compensate.

Eventually, the RAPIER engines will switch modes, and temporarily, some or all of your turbojets will spring back to life. Pitch carefully up to 45 degrees to get your apoapsis rising and break atmo ASAP. SAS should still keep you stable. If you're shooting for a 100km orbit, your apoapsis will get there before your jets completely flame out. Group 3 will shut them down and close all intakes.

If you're going higher, might as well leave the jets on until they flame out completely, then hit group 3. Once your apoapsis hits the desired point, kill your engines. This might be a good point to open the docking port and solar panels with group 0. You may need to goose your engines a bit to keep your apoapsis from dropping below where you want it as you continue rising through the stratosphere. Eventually, circularize.

Descent: The fuel in the FL-T800 should be enough to get you home, and the oxidizer in it should help keep your center of gravity forward for stability during descent. (Don't forget to enable the fuel feed from that tank.) If you want to do a little flying around (or, like me, you have trouble with precision deorbiting), put fuel back in the main tank as necessary.

Use your deorbit burn to lower your periapsis to about 40km. Once you've done that, hit 3 again to reopen all intakes, then 4 to shut down the RAPIER engines and reactivate the turbojets. That should be plenty of thrust for flying and landing, but if you want more, 5 will reactivate the RAPIER engines and toggle them back to air breathing mode. Don't forget to close the docking port and solar panels above 30km. Let your speed bleed off to the point you're comfortable flying, apply thrust, and bring it home. Use groups 1 and 2 to toggle your intakes, using them as airbrakes as necessary.

Download

ODV-2 is derived from FDV-3B, has been similarly updated with additional jet fuel tanks in place of structural fuselages, and the RAPIER engines and turbojet engines on the payload sections have been swapped for stability and simplicity's sake. Someone smacked the engineer who felt sorry for the pile of neglected basic jet engines, and put a turbojet on the centerline instead of the previous basic jet. Some other minor changes were made to aerodynamics and landing gear. With these changes, she can deliver ~4700 fuel, ~5400 ox, 1500 monoprop and 2 kerbals to 100km orbit, with pilot, reserve FL-T800, and some leftover fuel in the jet fuel tanks; a notable improvement upon her predecessor. Still 312 parts, still causes a fair amount of time dilation on my PC, but much friendlier to fly. Her only downside compared to her predecessor is that grouped RAPIER engines in closed-cycle mode overheat easily, so she has to be throttled back to 80% to keep them from exploding. (The first time that happened while I was watching orbital view was a surprise, let me tell you.)

Ascent: Before takeoff, activate SAS and resource display, throttle up to max, close two intake groups with action groups 1 and 2. This leaves a total of 16 intakes open at takeoff to feed the 17 engines. Spacebar to get the party started. Only hit it once, or you'll punch off your nose gear! She isn't safe to take off or land without it.

Pay attention during your takeoff roll; I've noted that *occasionally* the wings flex unpredictably and try to send you off the side of the runway, possibly due to the landing gear changes. Arrest any motion by attempting to rotate early.

If there's no trouble, rotate at the first set of marks on the far end of the runway. Careful--it takes a short bit to get the nose up, but once it is, it's easy to over-rotate and start tumbling. After liftoff, gear up and 50 degrees AOA. It's a slow ascent, so 2x time compression is safe as far as I can tell, but more introduces a strange wobble for me. Open intake group 1 at 13km, and group 2 at 17km. Stop using time compression here, if applicable.

Start pitching forward at 19km so you hit zero AOA at 20km. The ship will continue to rise while you accelerate. As your rate of climb approaches zero, pitch up 10 degrees (and maintain this AOA) to maintain a very slow climb until your ship starts to flame ever so slightly, then pitch up to 13 degrees to start a slightly faster climb. You want to be flaming only a little bit through your climb, so if the flames get bright, pitch up to 15 degrees, or if they go out before 30km, pitch down to 10 degrees.

Once you reach 30km, pitch down to 8 degrees or so to maintain your rate of climb. You still want to be flaming slightly, but after this point, it's OK if the flames vanish. When your yaw starts to get dangerous due to flameouts, hit 9 to shut down the outer four turbojets. When your yaw gets dangerous again, activate RCS; the Vernor thrusters should add enough attitude control authority to prevent spins at full throttle. You may re-stabilize as you continue to accelerate, so feel free to deactivate and reactivate RCS as necessary to preserve fuel.

Try to get to 1900+ m/s surface speed. Past this point, acceleration becomes really slow, so if the RAPIER engines don't automatically switch modes by then and you're getting impatient, feel free to start pitching up at any time to force the change.

Eventually, the RAPIER engines will switch modes, and temporarily, some of the turbojets will spring back to life. Pitch up to 45 degrees to get your apoapsis rising, and lower your throttle to 80% to prevent the RAPIER engines from overheating. SAS and RCS should still keep you stable. Once you've reached the desired apoapsis (with a ~10k cushion to account for remaining atmospheric drag), group 3 will shut down all jets and toggle all intakes closed. Disable RCS and kill your thrust. Above 72k would be a good time to deploy the Gigantors with group 0. Finally, circularize.

Descent: If you consider the Jumbo-64s your payload and empty them entirely, deorbit using the nose tank (enable the fuel and ox flow from it, of course), and return to atmospheric flight nearish KSC, the remaining fuel in the Mk1 fuselages should be enough to get you home, and the fuel and oxidizer left in the nose FLT-800 should keep your center of gravity forward for stability during descent.

Use your deorbit burn to lower your periapsis to about 40km. Once you've done that, hit 3 again to reopen all intakes, then 4 to shut down the RAPIER engines and reactivate the turbojets. Don't forget to close the docking port and solar panels above 30km. Let your speed bleed off to the point you're comfortable flying, apply thrust, and bring it home. Use groups 1 and 2 to toggle your intakes, using them as airbrakes as necessary.

Download

I tried making a version of ODV-1 with the engine layout of ODV-2, but I think ODV-1's best feature is how stable it is during ascent, and swapping the engines around thus really screwed with its stability, not to mention requiring heat management. For manual control, it's way better the way it is.

Cheers!

Edited September 8, 2014 by Athos

[Pds314]

The number of air intakes is..... Absolutely, beyond any semblance of doubt, insane.

[O-Doc]

The number of air intakes is..... Absolutely, beyond any semblance of doubt, insane.

I have to agree with this. There's plenty of advice around these forums regarding how you can spam even more intakes. I personally would like to see your intake spamming technique evolve into something more aesthetic.

Looks like you're having fun so, rep to you.

[Athos]

I have to agree with this. There's plenty of advice around these forums regarding how you can spam even more intakes. I personally would like to see your intake spamming technique evolve into something more aesthetic.

Looks like you're having fun so, rep to you.

Thank you! Yes, I know it's a lot. I've tried to keep it down to about 4 per engine. The light SSTO has that, the heavy one has 8 engines and 9 groups of 4 intakes, the super-heavy one has 17 engines and 18 groups of 4 intakes.

I know what you mean about aesthetics; I see lots of craft with their internals sandwiched between two layers of wing connectors, for example. My larger builds tend to be wide since they don't do that, and it's not the prettiest. But it keeps the part count down and they are still pretty easy to fly on manual control, and that was really what I was going for.

I sort of like the method of 4x intakes on a quad-connector and a cubic octagonal strut, for larger builds. They don't look so great mounted on a wing leading edge, granted, but inside the wing with two intakes above and below, it looks nicer. And I find it easier than spamming single intakes all over the place, so far at least.

[O-Doc]

I personally disregard any "rules" when playing this game and make craft I enjoy. Some spam intakes, some don't. I just want to have fun flying them.

Btw, I think my most spammy craft has 16 intakes per turbo and two units of lift rating per ton LOL!

[soulreaver1981]

You call that intake spamming???

Thats noting lol.

take a look a mine planes