Tutorial:Aeris 4A mission
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.
Before we get into space, the Aeris 4A takes off and flies just like a regular plane.
- Activate SAS
- Activate jet engines (Default Hotkey: 5)
- Throttle to 100% (Default Hotkey: Z)
- 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%
Congratulations, you flew a plane into orbit! You can now stay in space forever, until you voluntarily fire your engines to deorbit yourself.
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.
- 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.
Congratulations! You went to orbit and back! In a plane! And you didn’t jettison any parts during the journey!