How to get a Space Shuttle down from orbit?

[TronX33]

So, i had a Space Shuttle replica made by Naito up in orbit in a 170km x 170km orbit, about to land at KSC. However, during reentry, my wings exploded due to overheating, as well as the cargo bay, and mono-propellant tanks. The craft says that it's compatible with KSP 1.0.4. Should I just set ignore max temperature and unbreakable joints? Should I go in like the real shuttle, or go in nose first?

[ajburges]

To just land a space plane:

> Deorbit burn to an orbit with a Pe of 45 km.

> Hold an AoA of 25-40° until the atmosphere really bites at 20 km.

> Maintain a AoA above the horizon until Mach 4.

> Manuver normally around Mach 2.

Target your entry by varying the timing of your burn with the same flight profile.

[capi3101]

If you have access to airbrakes, include them on your design; they'll help you lose speed without gaining a great deal of heat. Other than that, what ajburges said; it'd also help to know if you're using FAR or stock air.

[TronX33]

If you have access to airbrakes, include them on your design; they'll help you lose speed without gaining a great deal of heat. Other than that, what ajburges said; it'd also help to know if you're using FAR or stock air.

I'm using stock air. So will what ajburnes said help me avoid my wings exploding? And if I'm supposed to make a 45 km high orbit, how do I target the KSC?

[ajburges]

I'm using stock air. So will what ajburnes said help me avoid my wings exploding? And if I'm supposed to make a 45 km high orbit, how do I target the KSC?

Targeting your landing is about learning the phase angle between your deorbit burn and landing site. The amount of lift and drag your craft has along with flight profile can make a difference of up to half Kerbin's circumference! Most folks learn their reentry from a fixed altitude (around 80 km) or use predictive tools to estimate atmospheric trajectory.

If you can save and load, deorbit once or twice and note where you wind up WRT the original Pe you set. I recommend starting with the Pe above your landing site. Unpowered landings are much tougher than powered decent. You only really get one shot at landing at your chosen site and energy management becomes critical to realize any cross-range capabilities.

[I_Killed_Jeb]

I find that a Pe of 55 km approx opposite of KSC from an 85x85 orbit allows a very nice unpowered glide into the runway in a well-lifted, aibraked craft without too much concern for heat.

Source: 10 hours of playtesting SSTO re-entries in 1.0.4

[almagnus1]

Part of the Shuttle reentry involved S Turns, which is essentially putting the bottom of your space plane into the prograde vector while pointing your nose to the left or right, essentially making giant S's to bleed off speed in the 20k-30k region, where the atmosphere is biting in. You'd then turn the other way, so you can correct the change in trajectory (thus flying an "S", hence the maneuver name).

If you can learn to do this, it can help to slow you down. Expect to see SSTO confetti when learning though, as it's really easy to get TOO aggressive with this maneuver and rip the plane apart, especially with FAR installed.

Edit: You may want to read https://en.wikipedia.org/wiki/Space_Shuttle#Re-entry_and_landing, as this goes into detail on what I'm failing at describing XD

Edited July 28, 2015 by almagnus1

[AaronLS]

Part of why angling up is helpful, other than bleeding off speed, is it keeps your altitude from dropping as quickly. Therefore you stay in thinner atmosphere and have more time to lose speed before dropping to thicker atmosphere.

There's kind of a sweet spot as burges points out. In thinner upper atmosphere it is a very high angle of 30-40, but around 20km altitude you'd be pointed just above the horizon a few degrees. You can watch the little dial at the top that shows your vertical drop rate, and try to find the angle that minimizes that(keeps it as close to the 0 marker as possible, although you won't be able to get it very close to 0 descent rate, just that you are trying to find the angle where you aren't dropping as quickly).

Also, when you drop your 170km orbit periapsis down into the atmosphere, don't drop it very deep or you will come in too steeply and reach thick atmosphere too quickly.

I usually don't drop my periapsis below 55k, but if I'm coming in really hot from a high apoapsis, I'll only do 60 or 65k. In those cases it might happen that it takes multiple orbits skimming the atmosphere to slow down.

[ajburges]

As I said, sticking to a common decent profile really helps in reaching a specific landing zone, but what you use is up to you.

A Pe of 45 km works well because there is a noticeable increase in drag at 50 km. Without additional thrust, anything that dips that low is going down somewhere near Pe with correct flight profile. Spend too long too high and variances make it hard to predict landing site. I also strongly recommend keeping it above 36 km. That's about the height where lift starts to work. You want to linger there so let drag, not orbital momentum, take you there. Anything at our below 20 km is crazy. You are getting to the danger zone on orbital momentum alone and not allowing drag to do much work for you.

For fun, the extended mission for one of my cheap probes was a radial return from Minmus orbit. I added 500 m/s at the start to target KSC directly and another 1 km/s before reentry. I think it popped without any heat guages at about 36 km. It was relatively fine until that point.

[TronX33]

As I said, sticking to a common decent profile really helps in reaching a specific landing zone, but what you use is up to you.

A Pe of 45 km works well because there is a noticeable increase in drag at 50 km. Without additional thrust, anything that dips that low is going down somewhere near Pe with correct flight profile. Spend too long too high and variances make it hard to predict landing site. I also strongly recommend keeping it above 36 km. That's about the height where lift starts to work. You want to linger there so let drag, not orbital momentum, take you there. Anything at our below 20 km is crazy. You are getting to the danger zone on orbital momentum alone and not allowing drag to do much work for you.

For fun, the extended mission for one of my cheap probes was a radial return from Minmus orbit. I added 500 m/s at the start to target KSC directly and another 1 km/s before reentry. I think it popped without any heat guages at about 36 km. It was relatively fine until that point.

Thanks for the tidbit about the atmosphere and lift! It will greatly help me in the future.

Part of why angling up is helpful, other than bleeding off speed, is it keeps your altitude from dropping as quickly. Therefore you stay in thinner atmosphere and have more time to lose speed before dropping to thicker atmosphere.

There's kind of a sweet spot as burges points out. In thinner upper atmosphere it is a very high angle of 30-40, but around 20km altitude you'd be pointed just above the horizon a few degrees. You can watch the little dial at the top that shows your vertical drop rate, and try to find the angle that minimizes that(keeps it as close to the 0 marker as possible, although you won't be able to get it very close to 0 descent rate, just that you are trying to find the angle where you aren't dropping as quickly).

Also, when you drop your 170km orbit periapsis down into the atmosphere, don't drop it very deep or you will come in too steeply and reach thick atmosphere too quickly.

I usually don't drop my periapsis below 55k, but if I'm coming in really hot from a high apoapsis, I'll only do 60 or 65k. In those cases it might happen that it takes multiple orbits skimming the atmosphere to slow down.

Ah, ok, so have to let it slow down gradually high in the atmosphere. I was applying what I knew for planning capsule re-entries to space-plane re-entries.

Rep for you, ajburges, and pretty much everyone else who responded

[Vegetal]

I seem to use a much more aggressive re-entry profile than people around here. In my usual 80km orbits, I retro burn 90 degrees before KSC, and my periapsis is well into the ground, just some 100km after KSC. Things get hot, but i can keep it under control by pitching the aircraft up when it gets too hot.

It's definitely more dangerous, but as I fly a lot of different space planes, I found this approach easier to do accurately for any aircraft, as it is done closer to the target and in a more direct fashion.

[luizopiloto]

I have a MK3 shuttle I use a lot. The reentry profile: Lower orbit to ~75K meters, when above the Pyramids spot, burn retrograde until the orbital path goes 200km west from KSC... orbital speed goes down to ~1890m/s... Maintain an angle of attack of 30° until vertical speed drops to -50m/s (this happens around 28K meters altitude)... then start to lower AoA to maintain VS between -10~-40m/s... Shuttle glides and slowly looses speed, until it reaches KSC...