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

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(→‎Ascent to Orbit)
 
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{{Outdated|The changes to the atmosphere and aerodynamics in 1.0 mean that this article is almost certainly outdated at present.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.
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[[File:Aeris 4A on runway.png|thumb|The Aeris 4A ready to start]]
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* 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.
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* Safe re-entry may also be problematic.
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This guide will help you fly the [[Aeris 4A]] into orbit, and land back at the KSC runway.
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* This was a fairly easy mission pre-1.0, but it's now looking like it's going to be quite difficult.
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See the [[{{TALKPAGENAME}}#1.0_ascent_profile|talk page]] for current status and discussion.
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The Aeris 4A is an SSTO spaceplane that has air-breathing Turbo Ramjet Engines for use at lower altitude and speed, while a Toroidal Aerospike Engine takes over when the ramjets become ineffective.
 +
 
 +
For simplicity, this guide will call the Turbo Ramjet Engines “jet engines”, and the Toroidal Aerospike will simply be called “rocket engine”.
 +
 
 +
This guide assumes that you have never flown a spaceplane into orbit before, but some of the details here should be interesting for experienced KSP players as well. Hopefully, this guide will help you become familiar with the operational principle of air-breathing SSTO spaceplanes, allowing you to not only be able to fly the Aeris 4A, but also design much better vehicles of your own.
  
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--[[User:Murph|Murph]] ([[User talk:Murph|talk]]) 18:09, 3 May 2015 (UTC)
 
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}}
 
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[[File:Aeris 4A on runway.png|thumb|The Aeris 4A ready to start]]
 
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This is an outline for a typical mission with an [[Aeris 4A]] a SSTO.
 
  
 
== Takeoff ==
 
== Takeoff ==
  
−
# 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).
+
Before we get into space, the Aeris 4A takes off and flies just like a regular plane.
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# Activate turbojet engines with the 1 key.
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# Set throttle to 100%.
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# Activate SAS
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# Wait until you have achieved a speed of around 80–100 m/s.
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# Activate jet engines (Default Hotkey: 5)
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# 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).
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# Throttle to 100% (Default Hotkey: Z)
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# Gear up when clear of the runway.
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# Pull up after speed reaches 70m/s
 +
#: Note: Aeris 4A is not at risk of a tailstrike during takeoff, but it is still good form to pull up gently.
 +
# Gear up after altitude reaches 80m
 +
#: Note: The KSC Runway has an altitude of 70m and the altitude is read from the cockpit. Even with an altitude reading of 72 meters, the rear wheels may still be on the ground.
 +
 
 +
== Ascent to Orbit ==
 +
 
 +
In case you didn’t know, being in orbit means that you are in free fall (i.e. being accelerated toward the surface of the planet by gravity, just as a skydiver would be) but your pro-grade velocity (speed in the direction you are traveling around the planet) is so high that you keep missing the planet's surface. So, basically, you're falling ''around'' the planet.
 +
 
 +
You will need a pro-grade velocity of around 2270m/s to acheive orbit. You will also want to be above 70km; under 70km, air resistance will slowly eat away at the speed you worked so hard to gain; above 70km, there is no air resistance, and your speed won’t be lost. Thus, you stay in space forever without having to expend fuel.
 +
 
 +
So let’s start spinning around our planet by heading eastward.
 +
 
 +
# Maintain a heading of 90 (East)
 +
#: Note: Because the planet Kerbin spins eastward at 175m/s, it means that you get 175m/s for free when entering into a west-to-east orbit. While the Aeris 4A is capable of entering into a different orbit, the procedure will be different, and this guide will only cover getting into the simplest west-to-east orbit.
 +
# Keep aircraft nose pointed 15 degrees above the horizon
 +
# When altitude exceeds 18km, and speed exceeds 1380m/s, active rocket engine (Default Hotkey: 6)
 +
#: Note: The Aeris 4A’s jet engines are 11 times more fuel efficient than the rocket engine, so we want to use them for as long as possible.
 +
# Keep aircraft nose pointed 10 degrees above the horizon
 +
# Go into map view (Default Hotkey: M)
 +
# When apoapsis reaches 80km, cut throttle to 0% (Default Hotkey: X)
 +
# Keep aircraft nose pointed prograde
 +
# Coast toward apoapsis
 +
# About 10 seconds before arriving at apoapsis, throttle back up to 100% again, and keep nose pointed prograde
 +
# When periapsis rises to about 80km, set throttle to 0%
  
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== Atmospheric ascension ==
+
Congratulations, you flew a plane into orbit! You can now stay in space forever, until you voluntarily fire your engines to deorbit yourself.
  
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# Maintain 100% throttle.
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== Orbital Mission ==
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# Ascend with a nose angle around 30° above the horizon.  Your prograde vector will be somewhere around 10–20° with this nose angle.
 
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# Occasional tiny amounts of nose down input will be required to correct the pitch due to the curvature of the planet.
 
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# Watch your altitude, and intake air on the resources panel.
 
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# You should be able to ascend easily, gaining speed all the way, to 20,000m on the dual turbojets.
 
  
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== Orbital ascension ==
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The stock Aeris 4A can be used to perform theses missions:
  
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# 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.
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*Create crew reports and EVA reports, then send them back to Kerbin for Science Points.
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# Activate the liquid fuel engine with action group 2.
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*Transporting one Kerbal to another ship or space station.
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# 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.
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*Docking with and refueling another ship or space station.
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# Maintain 100% throttle.
 
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# 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.
 
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# Watch your apoapsis on the map view.
 
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# When your apoapsis reaches 100 km, set your throttle to 0%.
 
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# 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.
 
  
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== Orbital maneuvers ==
 
  
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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.
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If you want to get back to Kerbin from an 80km by 80km circular orbit, you will need this much fuel: 66 oxidizer and 54 liquid fuel.
  
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== Deorbiting ==
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== Deorbit and landing ==
  
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# 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.
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This part is hard. I am sorry to say that the Aeris 4A’s Mk1 cockpit is not very heat resistant, and very prone to burning up during reentry. To ensure safety, I suggest a long and arduous “skip reentry”.
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# 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.
 
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# Turn your craft to face prograde.
 
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# 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.
 
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# Shut down the rocket engine by right-clicking on it and selecting "Shutdown Engine"
 
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# Re-activate the air intakes with action group 3.
 
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# 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.
 
  
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== Re-Entry ==
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We will first get low in the atmosphere, bounce off (skip) to a pretty high altitude again, and then perform a second descent. The long and winding path traveled will spread the heat over a greater amount of time, and ensure survival.
  
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# 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.
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The long and winding path will also make an accurate landing at the KSC runway difficult. However, with practice, accurate unpowered landings can be consistently done.
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# 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.
 
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# When you are below 20,000m altitude and 400 m/s speed, you should be able to begin to fly normally again.
 
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# Wait until your speed is low enough, or altitude is becoming critical before attempting to convert to normal flight.
 
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# Put some power to the jet engines while pointing prograde and try to get into a level flight with constant speed.
 
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# Navigate to the KSC or find another suitable spot for landing.
 
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# 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.
 
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# When approaching KSC from the west, remember to keep above 5,000m until you are clear of the mountains.
 
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# 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.
 
  
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== Landing ==
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Imagine a point halfway across the ocean separating the KSC continent and the continent to its west, we will call this Location A. From Location A, imagine following the equator westward for a distance equal to 1/4 of Kerbin's circumference. This position, which is close to the giant impact crater, we will call Location B.
  
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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.  
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# When your orbital path takes you above Location B, start burning retrograde.
 +
# When your current projected path ends at Location A, stop the burn.
 +
# Deactivate the engines.
 +
#: Note: Because they don't don’t work in space, you may not realize the jet engines are still on.
 +
# Keep your nose pointed prograde as you descend through the atmosphere.
 +
# When your altitude reaches 35km, start pulling up gently.
 +
# When your nose is stable at about 10 degrees above the horizon, pull up hard and keep it pulled.
 +
#: Note: The large delta wing will ensure you won’t backflip. If you eased into this maneuver gently your nose won’t oscillate up and down.
 +
# Around 43km you will begin descending again. Point the nose back down until it is aligned with prograde.
 +
# Nose up if you think you will undershoot the KSC runway; nose down if you think you will overshoot. Make yaw and roll adjustments as needed. If you need to lose speed, use the “nose up and down” maneuver, but don’t do it too hard, or you will rip your wings off.
 +
#: Note: If you end up too far off course to glide, you can try to reignite your jet engines and do a powered flight back to the KSC.
 +
# For a gentle landing, you should hit the runway at less than 100m/s airspeed, and less than 5m/s vertical speed. Apply wheel brakes (Default Hotkey: Hold B) to come to a full stop.
  
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# 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°.
+
Congratulations! You went to orbit and back! In a plane! And you didn’t jettison any parts during the journey!
−
# Switching to the chase camera view can be quite helpful when flying an approach and landing.
 
−
# Go in slow, very low, and at a very flat angle.
 
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# 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.
 
−
# An altitude of 500–1000m when 10 km out, and 250m when 5 km out should be good for a nice gentle final approach.
 
−
# 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.
 
−
# 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.
 
−
# 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°.
 
−
# Check your heading, it should be 090° or 270° on final approach.
 
−
# 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.
 
−
# 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.
 
−
# 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).
 
−
# If your vertical speed is too high, expect the engines (or more) to fall off on touchdown, if you don't just explode.
 
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# 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!
 
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# Throttle to 0% just before touchdown.
 
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# For a perfect landing, the rear wheels should gently touch down on, or just after, the "piano keys" at the start of the runway.
 
−
# Use the brakes to bring you to a halt.
 
−
# Congratulate yourself!
 
  
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[[Category:Tutorials|Tutorial:Aeris 4A mission]]
+
[[Category:Tutorials|Aeris 4A mission]]

Latest revision as of 00:16, 6 July 2020

The Aeris 4A ready to start

This guide will help you fly the Aeris 4A into orbit, and land back at the KSC runway.

The Aeris 4A is an SSTO spaceplane that has air-breathing Turbo Ramjet Engines for use at lower altitude and speed, while a Toroidal Aerospike Engine takes over when the ramjets become ineffective.

For simplicity, this guide will call the Turbo Ramjet Engines “jet engines”, and the Toroidal Aerospike will simply be called “rocket engine”.

This guide assumes that you have never flown a spaceplane into orbit before, but some of the details here should be interesting for experienced KSP players as well. Hopefully, this guide will help you become familiar with the operational principle of air-breathing SSTO spaceplanes, allowing you to not only be able to fly the Aeris 4A, but also design much better vehicles of your own.


Takeoff

Before we get into space, the Aeris 4A takes off and flies just like a regular plane.

  1. Activate SAS
  2. Activate jet engines (Default Hotkey: 5)
  3. Throttle to 100% (Default Hotkey: Z)
  4. Pull up after speed reaches 70m/s
    Note: Aeris 4A is not at risk of a tailstrike during takeoff, but it is still good form to pull up gently.
  5. Gear up after altitude reaches 80m
    Note: The KSC Runway has an altitude of 70m and the altitude is read from the cockpit. Even with an altitude reading of 72 meters, the rear wheels may still be on the ground.

Ascent to Orbit

In case you didn’t know, being in orbit means that you are in free fall (i.e. being accelerated toward the surface of the planet by gravity, just as a skydiver would be) but your pro-grade velocity (speed in the direction you are traveling around the planet) is so high that you keep missing the planet's surface. So, basically, you're falling around the planet.

You will need a pro-grade velocity of around 2270m/s to acheive orbit. You will also want to be above 70km; under 70km, air resistance will slowly eat away at the speed you worked so hard to gain; above 70km, there is no air resistance, and your speed won’t be lost. Thus, you stay in space forever without having to expend fuel.

So let’s start spinning around our planet by heading eastward.

  1. Maintain a heading of 90 (East)
    Note: Because the planet Kerbin spins eastward at 175m/s, it means that you get 175m/s for free when entering into a west-to-east orbit. While the Aeris 4A is capable of entering into a different orbit, the procedure will be different, and this guide will only cover getting into the simplest west-to-east orbit.
  2. Keep aircraft nose pointed 15 degrees above the horizon
  3. When altitude exceeds 18km, and speed exceeds 1380m/s, active rocket engine (Default Hotkey: 6)
    Note: The Aeris 4A’s jet engines are 11 times more fuel efficient than the rocket engine, so we want to use them for as long as possible.
  4. Keep aircraft nose pointed 10 degrees above the horizon
  5. Go into map view (Default Hotkey: M)
  6. When apoapsis reaches 80km, cut throttle to 0% (Default Hotkey: X)
  7. Keep aircraft nose pointed prograde
  8. Coast toward apoapsis
  9. About 10 seconds before arriving at apoapsis, throttle back up to 100% again, and keep nose pointed prograde
  10. When periapsis rises to about 80km, set throttle to 0%

Congratulations, you flew a plane into orbit! You can now stay in space forever, until you voluntarily fire your engines to deorbit yourself.

Orbital Mission

The stock Aeris 4A can be used to perform theses missions:

  • Create crew reports and EVA reports, then send them back to Kerbin for Science Points.
  • Transporting one Kerbal to another ship or space station.
  • Docking with and refueling another ship or space station.


If you want to get back to Kerbin from an 80km by 80km circular orbit, you will need this much fuel: 66 oxidizer and 54 liquid fuel.

Deorbit and landing

This part is hard. I am sorry to say that the Aeris 4A’s Mk1 cockpit is not very heat resistant, and very prone to burning up during reentry. To ensure safety, I suggest a long and arduous “skip reentry”.

We will first get low in the atmosphere, bounce off (skip) to a pretty high altitude again, and then perform a second descent. The long and winding path traveled will spread the heat over a greater amount of time, and ensure survival.

The long and winding path will also make an accurate landing at the KSC runway difficult. However, with practice, accurate unpowered landings can be consistently done.

Imagine a point halfway across the ocean separating the KSC continent and the continent to its west, we will call this Location A. From Location A, imagine following the equator westward for a distance equal to 1/4 of Kerbin's circumference. This position, which is close to the giant impact crater, we will call Location B.

  1. When your orbital path takes you above Location B, start burning retrograde.
  2. When your current projected path ends at Location A, stop the burn.
  3. Deactivate the engines.
    Note: Because they don't don’t work in space, you may not realize the jet engines are still on.
  4. Keep your nose pointed prograde as you descend through the atmosphere.
  5. When your altitude reaches 35km, start pulling up gently.
  6. When your nose is stable at about 10 degrees above the horizon, pull up hard and keep it pulled.
    Note: The large delta wing will ensure you won’t backflip. If you eased into this maneuver gently your nose won’t oscillate up and down.
  7. Around 43km you will begin descending again. Point the nose back down until it is aligned with prograde.
  8. Nose up if you think you will undershoot the KSC runway; nose down if you think you will overshoot. Make yaw and roll adjustments as needed. If you need to lose speed, use the “nose up and down” maneuver, but don’t do it too hard, or you will rip your wings off.
    Note: If you end up too far off course to glide, you can try to reignite your jet engines and do a powered flight back to the KSC.
  9. For a gentle landing, you should hit the runway at less than 100m/s airspeed, and less than 5m/s vertical speed. Apply wheel brakes (Default Hotkey: Hold B) to come to a full stop.

Congratulations! You went to orbit and back! In a plane! And you didn’t jettison any parts during the journey!

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