KerbalX

Details

• Type: VAB
• Class: ship
• Part Count: 52
• Mods: 3
• KSP: 1.12.5

Mods

• Cormorant Aeronology
• Squad (stock)
• TweakableEverything

History and Background

There were plans for a reusable space plane for as long as the beginning of the dream of spaceflight. The Space Race between the United States and Soviet Union technically began with the roughest definitions of space planes such as the X-15 which was launched via another aircraft. There were numerous plans for space planes launched from a rocket including the USAF’s Dyna-Soar (cancelled in the early 1960s) and the Soviet MIG-105. However this dream wasn’t realized until the beginning of the Nixon-era program in 1969 that eventually led to development of what became the Space Shuttle. The first orbiter, Enterprise, was finished in 1976 and went through several years of atmospheric tests with first space-capable orbiter, Columbia, finished several years later.

The launch of the Columbia on STS-1 in April 1981 began the lengthy and second-most expensive space program in history which lasted until the final mission of Space Shuttle Atlantis in July 2011. There were 135 space shuttle missions over a 30-year career with two tragic failures which saw the loss of the Challenger on January 28th, 1986 and the loss of Columbia on January 16th, 2003. This also led to the Space Shuttle unfortunately also leading the record of being the most deadly spacecraft to date. Both tragedies saw the loss of their entire crews, a total of 14 astronauts between the two disasters.

The Columbia in its earliest missions to test out the capabilities in Space Shuttle in orbit only had a crew of two pilots and the external fuel tank was painted white for protective purposes until they realized it wasn’t necessary which saved weight and gave the later shuttle missions one of its most designating features – an unpainted orange main fuel tank.

Basic Description

The CA Mk3 Shuttle STS-1XX uses primarily Cormorant Aeronology parts and is modified from the original craft made by its author, Pak. It was further adjusted using advice from drtedastro on modifying gimbals, setting up Mechjeb, and making it far easier to fly. I further adjusted it to approximate the earliest configuration of the Columbia during its first two missions including a white external tank. It is designed for short LKO (Low Kerbin Orbits) carrying up to four kerbonauts and minimal payload. The primary mission profile is to use it for training on how to fly the shuttle but it is rated for a payload of up to 10 tonnes and has enough power generated by the fuel cells to stay in orbit for a while if necessary.

I recommend that many of the shuttle operations are handled through Mechjeb as the shuttle was highly automated during much of its mission operation including launching, ascending, orbiting, and landing. It can be flown manually however it’d be quite a challenge for novice and intermediate players because of its further unique ascent profile.

I have included a MechJeb profile for my recommended settings which usually give me consistent results. You should feel free to play with my recommendations and if you find a more optimal profile then please let me know so I can possibly improve upon it. My recommendations for a planned orbit are between 100 and 130 km with drtedastro finding the most ideal to be between 125 and 128 km. The shuttle’s orbital maneuvering engines (OME) are monopropellent with a reasonable thrust of 100 kN but aren’t meant to be used outside of LKO. You’ll probably have around 400 to 480 dV by the time you have reached your planned initial orbit although that can vary based on the efficiency of your ascent profile.

While it’s reasonable to make some small orbital changes I recommend that you keep about 100 to 130 dV in reserve for when you plan your atmospheric re-entry and landing. If you actually deplete your fuel there isn’t a very small backup fuel source, normally used for the fuel cells, which might get you back into the atmosphere but there are no guarantees.

Launch, Ascent, and Orbital Procedures

The launch and ascent procedures are pretty complex to most spacecraft and the Space Shuttle in real life was one of the complicated spacecraft ever built. You should make sure the gimbals for the Space Shuttle Main Engines (SSME) and the Orbital Maneuvering Engines (OME) are locked before launching the shuttle. I also recommend that force rolling isn’t activated at least for a few seconds although it might not have a significant effect on your ascent if it’s activated when you launch.

The first step, much like in real life, is to fire the SSMEs for just a moment until the craft stabilizes. This is also the chance to initialize the first abort mode, Redundant Set Launch Sequencer (RSLS), which allows you to abort the mission simply by shutting down the SSMEs.

The second step involves firing the solid fuel boosters, releasing the launch clamps and beginning your lift-off. This begins one of the most dangerous phases of the ascent as you have to ride out the boosters before you can take further action. You should keep a straight vertical ascent and make your roll so that the top (or back) of the shuttle is facing your desired inclination. You may encounter some unwanted wobble and it might feel a bit unstable until you have built up some speed. It is critical that you don’t begin your gravity turn until around a velocity of 325 m/s or at least an altitude of 2.5 km or otherwise you’ll probably find yourself on a violently unstable trajectory which can only end tragically.

The third involves unlocking the SSME gimbals so that they can take part in the gravity turn which will begin around 2.5 km and 325 m/s. You may encounter some wobble when beginning the turn, especially if flying manually, but otherwise just continue the turn and wait for the boosters to finish their work. The shuttle should stabilize after a short while but may encounter some more wobble and instability in the last 20 to 30 seconds before the boosters are exhausted.

Once the boosters are exhausted and have been successfully decoupled you have reached a decision point where you can continue your ascent or resort to the second and most dangerous abort mode, Return to Launch Site (RLS). This abort mode has you decouple the boosters and initially continue your ascent. The most difficult part is to roll in a way that you can safely release the main fuel tank and establish a stable glide back to the ground for a landing. You should ideally be able to follow the normal landing procedure and return to the KSC runway but it’s entirely possible that you’ll need to pick another place to land. The window for this is to be a viable option is pretty short and generally unnecessary in KSP unless you have a significant SSME failure.

If you have chosen to continue your ascent then you should adjust the SSME throttle to avoid lowering your Time to Apoapsis (TOA) making sure that it raises up to and doesn’t go below about 45 seconds. Once you have reached that point you should be pretty confident in the shuttle’s ability to reach space with little to no further action required on your part. You might encounter a bit of wobble as the shuttle goes through the upper atmosphere although on many of my ascents it was completely smooth. You might be tempted to activate the RCS or lock the SSME gimbals but most actions will make the problem far worse and unnecessarily use up your fuel supplies.

When you are nearing the edge of space (between 69 and 70 km) and your projected apoapsis is getting close to your desired altitude you are ready to make your next couple of decisions. The first is possibly adjusting your thrust to as low as 40% to potentially save some fuel as you sail through the last bits of atmosphere which requires a bit of trial and error on your part. The second is whatever or you want to try and reach orbit or attempt the third abort mode known as Abort Once Around (AOA) .

The third abort mode, Abort Once Around (AOA), involves either making a single orbit or a sub-orbital trajectory and is available once it’s certain that you will reach space regardless of any hardware failures. This might become necessary if you have a significant SSME failure towards the end of your ascent procedure when reaching space is unavoidable. The rest of this abort mode procedure is very similar to your normal re-entry and landing procedure except that you might not be in the right position to make a landing at your desired target and will have to pick an alternative location to make your landing.

If you have chosen to continue your mission and reach orbit then this step begins once you have reached space and can calculate your orbital burn maneuvers. When it comes to the shuttle this can be handled in several ways – both historically and a-historically. Your options also might be limited if you are carrying a heavier payload and your main fuel tank has already been depleted. If that’s the case your only option at this point is to immediately decouple the empty main fuel tank and proceed entirely with the OMEs. The procedure for this approach is similar to most simple orbital burns and you simply burn prograde upon approaching your apoapsis usually dividing the burn time by half and starting your burn at that many seconds (or minutes or hours) prior to reaching your apoapsis.

If you still have fuel in your main fuel tank this gives you some additional options – the simplest approach being that if you have enough dV you can simply use the SSMEs for a single burn. However this leaves with the spent main fuel tank as orbital debris which you may accidentally, and tragically, encounter during your mission. I still recommend this for more novice players because of its simplicity or if you don’t yet feel comfortable with calculating multiple and more complicated burns.

The historical approach uses a mixture of both sets of engines with multiple burns to eventually reach your desired orbit. The SSMEs are fired either to exhaustion or until your periapsis is somewhere between 20 and 50 km giving you a considerable period of time between the shuttle will potentially hit the atmosphere again. You should then rotate the shuttle a bit and eject the spent main fuel tank – which will eventually re-enter that atmosphere and be destroyed – and then make a second burn with your OMEs to put yourself into a stable orbit. You might also make a couple of smaller burns with your OMEs over the course of your first orbit to reach your desired parameters.

Once you have reached some kind of stable orbit but before making additional burns you have the option for the last abort mode, Abort to Orbit (ATO) which can be made for a number of reasons including engine failures, insufficient fuel, or accidental damage to the engines. This may have a profound effect on your mission but affords you the opportunity to choose when and how you will re-enter that atmosphere and allow to make your planned landing. This was almost done on the STS-93 mission in July 1999 when one of the Columbia’s engines under-performed during the ascent although they were able to reach their planned orbit and complete their mission.

Re-Entry and Landing

You should have enough dV available through the OMEs to re-enter from LKO (Low Kerbin Orbit), and from an altitude of about 85km, you’ll need about 100 m/s of dV for a proper re-entry. You’ll need to turn off the OMEs (and lock their gimbals for good measure) when you re-enter, as they’ll be useless in the atmosphere.

Once you re-enter, you should pull about 40 degrees of AoA (Angle of Attack) so that the heat from the re-entry will be directed towards the tiles on the bottom of the shuttle, and otherwise just try and stay level.

When you reach about 30 - 40 km altitude, you should unlock the control surfaces and stay treating it as a glider – use broad s-turns to bleed off excessive speed and try and bring it down to 1000 m/s (or less). You’ll find the shuttle is quite a bit more controllable as you descend through the atmosphere and bleed off speed. You should aim for being at 800 to 1000 m/s when you hit somewhere between 20 and 30 km. You should deploy the speed brakes and try get down to 600 m/s around 15 km and as low as 200 m/s around 10 km.

You should have already picked your landing runway. I recommend KSC and either Runway 09 (towards the water) or Runway 27 (away from the water). When you reach 10 km, you begin your initial approach and further bleed your speed down to 120 m/s in preparation for your final approach.

Once you are about 1 - 3 km from your chosen runway, you should start your final approach by lowering the landing gear and making sure your speed is somewhere between stall speed and 120 m/s. The shuttle is pretty durable and can survive some pretty rough landings, even if you run off the runway. When you are within a few meters of the runway, you should level out and prepare to flare up, which means to raise up slightly to allow the rear wheels to touch the ground first. There is no drogue parachute on this early model of the shuttle (which wasn’t added until 1992) so managing your projected touchdown is critical. Once you have killed the throttle completely, you should gently pump on the brakes to slow down further and then fully brake to come to a complete stop.

Built in the VAB in KSP version 1.12.5.

MECHJEB Settings

Orbital Altitude: 128 (km)
Prevent Overheats ON
Limit Q to 35000 (pa)
Limit Acceleration to 35 (m/s)
Limit Throttle to 80
Force Roll to -180 / -180
Corrective Steering Gain 2.8

Turn Start Alt 2.5 (km)
Turn Start Velocity 325 (m/s)
Turn End Alt 80 (km)
Final Flight Path Angle 0
Turn Shape 60

Thrust Profile

80% @ Lift-Off
40% @ 70 km
100% @ Orbital Burn