[0.15 Stock]Horizontal take-off and landing SSTO "Dreamchaser"

[Temstar]

I aimed for the ultimate aim of SSTO - airline style horizontal take off and landing. After spending better part of the day working out the bugs I\'ve finally come up with a working craft.

Orbiting burn guideline:

1. Turn on Adv SAS to keep the plane centered on the runway, max throttle and hit that spacebar and listen to the turbojets roar into life. Being a big fat SSTO Dreamchaser is quite heavy, so no need to nose down on the runway.

2. The runway is actually a little bit above the ground. Nearing the end of the runway flip Adv SAS off and pitch up. As the wheels leave the runway the plane will nose up. Immediately switch Adv SAS back on and the plane will start climbing. Retract landing gear.

3. Pitch up to 45 degree angle and let it climb

4. At 8,000m, hit stage to fire up the aerospike rocket engine.

5. At 19,000m disengage the jet engines. Around this point there should be some pitch instability due to fuel being used up in the forward section of the side stacks and loss of effect from control surfaces. if Adv SAS can\'t handle it turn it off monumentally and control your pitch manually. The instability should be fairly short lasting.

6. Once apapsis is at 70,000m, do an engine cut off and perform a course correction and nose down to the horizon.

7. Wait till about T-30 seconds till AP and fire up the engines again to build speed, get to about 2,000 m/s and turn off the engine again if AP is still ahead of you.

8. Nearing the AP, fire the engine again for final circularisation.

I haven\'t touched C7 before so I\'m still practicing landing with a trainer, but this plane should have plenty of lift to glide down to KSC runway particularly with empty fuel tanks. The drogue parachutes are reinforced and rated for up to 130m/s for a 6G deceleration, do not deploy chutes at greater than 130m/s.

Rocket engine kicking in

Course correction and waiting for AP

[Mr_Orion]

Just a note; people don\'t like it when every single picture is in it\'s own spoilers marks. It means you need to click a lot; I suggest you have a single spoiler with all the images inside it.

[Androsynth]

This plane is awesome, and it taught me to use an aerospike engine.. however I\'m seemingly unable to reach orbit with it. Are you sure your instructions for piloting it are complete? I maintained the 45 degree angle specified for the entire trip - is that right? Also, your instructions don\'t mention the RCS. Do you use the RCS to finish making the orbit?

On my second attempt, I removed the RCS thrusters, fuel tanks, and secondary SAS modules, and made it up to a circular orbit with a ton of fuel to spare. Could probably land this baby on the moon. Thank you!

[Temstar]

No I don\'t use the RCS to reach orbit. I had intended to use this craft as a shuttle in the future when docking comes into play and the RCS will be for translation when docking. After all the whole point of SSTO is to get people and cargo cheaply into orbit by not dumping any rocket parts.

I originally put on SAS to counteract a mysterious yaw force. Eventually I discovered the reason: my fuel lines confused the game as KSP can\'t handle two fuel lines coming out of one tank, it will just use one of the two lines. This caused one side to hold more fuel than the other and hence the yaw. I fixed this issue but forgot to take the SAS off. After flying the plane without SAS I agree they\'re not needed.

It makes sense lightening the plane even by a slight bit will greatly improve fuel left upon reaching orbit. The hardest thing about making a SSTO both in real life and KSP is to get the propellant mass fraction high enough. For Earth a craft needs 25 to 1 ratio fuel to vehicle hardware ratio to be able to achieve SSTO. On Kerbin it\'s a lot less, I calculate the current incarnation of Dreamchaser to be:

Empty: 15.16

Take off: 25.76

So in other words, almost 42% of the planes takeoff weight is fuel. If you add on two SAS it becomes 16.76/27.36, which worsens the propellant mass fraction to slightly above 38%, hence why the plane suddenly have a lot more trouble reaching orbit. Surprisingly removing the SAS also seems to improve handling somehow as I suddenly feel a lot less 'phantom force' when in orbit.

Anyway back when I made Dreamchaser I didn\'t know about the brake button. Now that I do I realize I only need one drag parachute (if any). So in addition to removing SAS I\'ve cut down the number of parachute to 1.

I\'ve also made some improvement to the flight program:

[list type=decimal]

[li]Turn on Adv SAS to keep the plane centered on the runway, max throttle and hit ignition on the turbojets. Upon reaching the end of the runway turn off Adv SAS and pull back on the stick. Once the plane leaps off the end of the runway it will nose up. Alternatively if you miss the end just keep Adv SAS off and after gliding on the grass a bit it will pitch up.[/li]

[li]Pitch up to 60 degree angle and let it climb[/li]

[li]At 12,000m, hit stage to fire up the aerospike rocket engine[/li]

[li]At 19,000m disengage the jet engines[/li]

[li]At around 50,000m you will have an AP of about 60,000m. Disengage Adv SAS and pitch down to horizon. By the time you pitched down the AP will be about 70,000m which[/li]

[li]Keep your nose on the horizon and keep the engine running until 2,000m/s[/li]

[li]Wait till T-30 till AP and fire up the engine again to 22,000m/s. After that do small burn as you near AP for final circularisation[/li]

Manage to reach orbit with about 350 fuel left. Still room for improvement of course. The ideal will be to reach orbit with one continuous burn. If you find a better flight program let me know.

Attaches is the improved Dreamchaser Block II.

[Avros]

Awesome ship! I\'ve been toying around with the nose section to allow a few more exploration choices once the ship is out of fuel:

I\'ve swapped out the C7 cockpit for the stock MK1 command capsule mounted on a 1m MechJeb module with the HSTW Mun Rover (attached .craft file). Not the most aerodynamic looking machine, but it works.

I\'m still seeing quite a bit of unwanted control surface correction if AdvSAS is stuck on the thing, but it flies well without it.

I\'ve also managed to maintain SSTO and similar fuel efficiency (315 fuel after circularization).

[dnleek]

How the hell do you land this thing? My version is exactly the same, only I replaced the half tanks with full jet fuel tanks and the tail fins with vertical canards, and every time it hits the lowest atmosphere layer coming down from orbit it suddenly wants to pitch either nose up or nose down, and won\'t stay horizontal. Actually, now that I think of it, the half rocket tank is much lighter... hold on, I have to try some science.

[Avros]

I\'ve had the same problem. Especially after a full orbital trip, I find myself without sufficient fuel to stabilize the thing for a landing. (Hence switching the cockpit to a mun rover).

[dnleek]

Ah, I figured it out. I was just trying to pitch up too much since I was too worried about my downwards velocity, and ended up stalling the plane. I just glided it to a safe landing, though it did pitch nose up once on the way down. Ended up rolling to a stop right outside the hangar. I\'m pretty proud of that

[Temstar]

Pitch up or down during reentry is a sign of too much weight at the rear of the plane I think. It\'s like how a shuttlecock always turn so that the heavy end faces downwards as it falls. All that fuel at the back of the plane plus three dead engines is really pushing the rear of the plane forwards fighting the control surfaces to get in front.

If you have a lot of fuel left it would be a good idea to do some non-necessary orbital maneuvers to burn up the excess fuel before attempting reentry.

Maybe they should give us a fuel dumping gadget in the future. =P

[TornadoEvil]

I managed to create a larger version of this craft, its much heavier but manages to get to orbit with 1000+ fuel and a few doodads.

It uses a similar ascent profile.

1)Throttle to full and reach about 100m/s

2)nose up to 10 - 20 degrees and pull off the runway (to aggressive a rotation will destroy the turbojets)

3)Slowly nose up to about 45 degrees and hold using sas to approx. 10km

4)Activate the Aerospikes

5)Deactivate the back center tank at around 22k to kill all 3 turbojets simultaneously, the tank should be about empty

6)Do whatever orbital insertion pleases you

7)Should have enough fuel and rcs to do whatever pleases you (except maybe landing it on mun, though you can orbit mun)

You can cut down the weight a bit from this version to boost performance (nosecones, rcs, a couple winglets)

I have not successfully landed it yet.

[Baneblade]

This is one of the most practical looking spaceplanes I have seen yet. Very nice job!

I decided to try it myself and designed a similar looking craft. It is a bit larger, but manages a bare orbit with around 400kg of fuel left (even with terrible piloting).

Despite my utter lack of knowledge in the building, flight, and de-orbiting of spaceplanes, my journey was somewhat successful.

Following several design iterations just to have a successful takeoff, my first orbital flight was white-knuckle the whole way. A slight construction fail meant the fuel drained from the rear tanks first, which made the whole plane nose-heavy. This is especially fun around 30,000m, where ramjets or control surfaces are no help to the slow pitchdown.

After boucing twice between 20,000 to 35,000m I finally boosted into a 70km circular(-ish) orbit. Not one orbit later, I decided to deorbit. Despite my totally uninformed guess, I still managed to land on the same continent as KSC. Only clipped two of the engines on the first successful landing too. ;D

Pictures for the picture god:

[Androsynth]

Any plans to rebuild either of these in 0.16?

[noneyabidnis]

This is one of the only crafts I\'ve seen available for download that use the ram jet things. Do they really make a difference? If so, what\'s their most effective use / purpose?