Difference between revisions of "Tutorial:Aeris 4A mission"

Revision as of 18:09, 3 May 2015

This page or section is in need of being brought up to date. Please help Kerbal Space Program Wiki by fixing inaccurate or outdated information. The changes to the atmosphere and aerodynamics in 1.0 mean that this article is almost certainly outdated at present. I'm planning on spending another bunch of time quite soon, evaluating the plane under the new physics. A continuous 30° ascent profile will likely be problematic somewhere in the 10–20km altitude range, due to heating from atmospheric friction. Interim recommendation: pull up to a steeper ascent, and/or reduce throttle at the phase(s) of the ascent that seem problematic for excessive heating. Safe re-entry may also be problematic. This was a fairly easy mission pre-1.0, but it's now looking like it's going to be quite difficult. See the talk page for current status and discussion. --Murph (talk) 18:09, 3 May 2015 (UTC)

The Aeris 4A ready to start

This is an outline for a typical mission with an Aeris 4A a SSTO.

Takeoff

1. Activate SAS (holding the brakes on while doing this will prevent the small chance of the SAS locking onto a slightly false velocity vector and causing a crash during rollout).
2. Activate turbojet engines with the 1 key.
3. Set throttle to 100%.
4. Wait until you have achieved a speed of around 80–100 m/s.
5. Raise the nose very carefully to avoid striking the runway with the liquid fuel engine (this can be significantly improved by replacing the supplied LV-T30 Liquid Fuel Engine engine with the Toroidal Aerospike Rocket, without any significant downside).
6. Gear up when clear of the runway.

Atmospheric ascension

1. Maintain 100% throttle.
2. Ascend with a nose angle around 30° above the horizon. Your prograde vector will be somewhere around 10–20° with this nose angle.
3. Occasional tiny amounts of nose down input will be required to correct the pitch due to the curvature of the planet.
4. Watch your altitude, and intake air on the resources panel.
5. You should be able to ascend easily, gaining speed all the way, to 20,000m on the dual turbojets.

Orbital ascension

1. When your intake air level reaches 0.07 (or at around 20,000m altitude), it is necessary to change from the turbojets over to the rocket engine.
2. Activate the liquid fuel engine with action group 2.
3. Shutdown the jets and close the intakes with action group 3 to avoid an asymmetric flame-out. Intake air starvation will occur somewhere around 22,000m.
4. Maintain 100% throttle.
5. Continue to ascend at an angle of around 30° above the horizon, applying occasional small amounts of nose down to follow the curvature of the planet.
6. Watch your apoapsis on the map view.
7. When your apoapsis reaches 100 km, set your throttle to 0%.
8. Wait until you've reached your apoapsis and circularize your orbit with a prograde burn. If the ascent went well, this should be a fairly short burn, probably somewhere around 10s.

Orbital maneuvers

You can now do an EVA or attempt to rendezvous and dock with another craft in orbit, but try not to use too much liquid fuel, as you will need some left for deorbiting.

Deorbiting

1. To land at (or at least near) the KSC, perform your deorbit burn when you are approximately over the large impact crater. Burn retrograde until your trajectory hits the continent east of the KSC.
2. Alternatively, perform your deorbit burn when KSC is on the directly opposite side of the planet, i.e. 180° from your current position. Burn retrograde until your new periapsis is at approximately 35 km directly over KSC. Once atmospheric drag is accounted for, this should bring you down below 20,000m (where you can regain atmospheric flight control) a little to the west of KSC, and about 5–10,000m approaching the mountains.
3. Turn your craft to face prograde.
4. Due to a construction mistake the jet engines won't work when there is no liquid fuel in the tanks connected to them They can't take fuel from the central tank. So pump the liquid fuel from the central jet fuel tank into the two outer FL-T400 tanks before you proceed. Make sure that the distribution between them is as equal as possible to avoid moving your center of mass to the side.
5. Shut down the rocket engine by right-clicking on it and selecting "Shutdown Engine"
6. Re-activate the air intakes with action group 3.
7. Re-activate the jet engines with action group 1, but do not activate throttle until you have intake air again, at 20,000m or lower altitude.

Re-Entry

1. You will start to notice atmospheric drag significantly reducing your speed at about 40,000m height. This will continue to have significant effects down to around 20,000m.
2. From now on, keep the roll parallel to the horizon and the nose pointed at, or just above the prograde marker on the nav-ball at all times.
3. When you are below 20,000m altitude and 400 m/s speed, you should be able to begin to fly normally again.
4. Wait until your speed is low enough, or altitude is becoming critical before attempting to convert to normal flight.
5. Put some power to the jet engines while pointing prograde and try to get into a level flight with constant speed.
6. Navigate to the KSC or find another suitable spot for landing.
7. With some practice on getting the deorbit burn from a circular 100 km orbit timed just right, it is possible to regain atmospheric flight control at around 15–20,000m altitude, and be in a controlled straight and level flight at 10,000m just in time to start a gentle controlled descent and approach for landing on the KSC runway.
8. When approaching KSC from the west, remember to keep above 5,000m until you are clear of the mountains.
9. Since you are probably low-ish on fuel, keep the throttle somewhere in the range of 33–66% (lower is usually better), while flying in, for maximum fuel efficiency (you use significantly more fuel fighting air resistance at higher speeds). Reduce throttle to 20% or less (or even 0%) when descending.

Landing

You do not necessarily need to land on the runway. Try it when you want to show off, but landing on the flat plain around the KSC is much easier.

1. Planting a flag on the grass at each end of the runway can help you find it and line up with it from a distance. The runway is 09/27, i.e. 090° or 270°.
2. Switching to the chase camera view can be quite helpful when flying an approach and landing.
3. Go in slow, very low, and at a very flat angle.
4. Plan to be established on a controlled, stable approach at around 10 km out from the runway, and certainly no later than 5 km out. If approaching from the west, this means as soon as reasonably possible after you clear the mountains, but is possible without a violent descent.
5. An altitude of 500–1000m when 10 km out, and 250m when 5 km out should be good for a nice gentle final approach.
6. If you are unstable between 5 km and the runway, or very badly aligned to the runway at that point, it's usually better to go around and try again, if you have the fuel to do so. Try to avoid violent control inputs on the last 5 km of approach.
7. Make sure the landing gear is down, and the gear lights are on if it's dark (they are very helpful to let you see the terrain and runway approaching on low finals). Enabling the parking brakes at this point or earlier can make sure that you brake as soon as you touch the ground, having one thing less to worry about. There's difference in locking the brakes before touchdown or holding down the brake key after touchdown.
8. On final approach, a speed of 60–100 m/s should be good, with a vertical speed of less than 5 m/s, nose up 5–10°.
9. Check your heading, it should be 090° or 270° on final approach.
10. Gradually reduce the speed while trying to remain level until you very gently drop to the ground while your nose is still pointing slightly upwards. Don't try to kill lots of speed at the last moment, it's probably not going to work. Get the speed fully under control by 5 km out, if possible.
11. Ideally you should gently touch down on the rear wheels only, with the nose up 5–10°, then the front wheel. Front wheel (or all 3) first is both very bad style; and can be uncontrollable, resulting in a crash.
12. If the nose is too high at touchdown, you may strike the LV-T30 on the runway (unless you replaced it with the Toroidal Aerospike, as suggested earlier).
13. If your vertical speed is too high, expect the engines (or more) to fall off on touchdown, if you don't just explode.
14. It's a long runway, don't try to force the plane down. Better to touch down a little late than leave smoking wreckage on the threshold!
15. Throttle to 0% just before touchdown.
16. For a perfect landing, the rear wheels should gently touch down on, or just after, the "piano keys" at the start of the runway.
17. Use the brakes to bring you to a halt.
18. Congratulate yourself!