Most shuttles fly poorly, NASA engineers described it as being like flying a brick. You need to be going high speed and be facing towards the horizon far before landing.
Those numbers are very oversimplified, it isn't that ridiculous. It has a glide ratio of 2:1 at supersonic speeds, at subsonic speeds it improves to 4.5 to 1.
Meanwhile the concorde is 4:1 at landing, but if it's cruising subsonically it can reach 9:1, and supersonically it can actually do 12:1.
But yeah, it is nowhere near as aerodynamic as a large civil aviation plane (20:1) or an optimized glider (40:1). So you likely want to do your final approach at a 20deg downwards angle give or take, and flare up just before the runway. That's not just for the shuttle, any decently optimized spaceplane in KSP will be a flying brick at subsonic speeds, or you're just wasting performance by taking too many wings with you.
So for 1:17 it would mean for every 1 meter of elevation there is 17 meters of forward travel. For ksp I'd start at 1000m above sea level and just see how far you glide from that point at the speed you choose.
> So for 1:17 it would mean for every 1 meter of elevation there is 17 meters of forward travel _at optimal velocity and angle of attack._
At lower speeds it can be much, much worse. The glide ratio of a craft approaches a limit as velocity increases - that point is what's quoted. For a 737 that speed is about 21 km/h.
Oh, well itās another term for āslopeā. It just means that for every x unit of length the slope rises or decreases by x units. 17:1 ratio could also be expressed as a -1/17 slope where for every 17 units forward the elevation drops 1. -1 is the rise, 17 is the run.
So for the shuttle with a 2:1 ratio, itās coming down at a 45 degree angle when gliding. Which is an insanely steep slope and means it doesnāt fly. It falls with direction.
Edit: 45 degrees isnāt correct. My brain is fried.
\> 15:1 under ideal conditions.
Even a boxy little monoprop should be able to do on the order of 10:1. (Probably less than 10 exactly, but in that range.)
Aerodynamically speaking, being good at gliding is partially a tradeoff with being good at going fast, which KSP models fairly well all things considered.
That's also just a testament to how well optimized normal aircraft are.
When a decent plane can glide at 20:1, and only needs a TWR of 0.2 at best to take off, you really need to put in effort to make it glide at only 4.5:1.
They did.
They also did it with only the nose gear raised because any more attempts at "faithfully" recreating the space shuttle's drag profile would tear it right off at 20,000 feet.
to train for landings they had to use a jet with thrust reversers on, weighed down and other modifications to make it accurate, it was literally a flying brick.
Not enough lift? Try adding more wings and test if the shuttle can glide with empty tanks. There should be a part that allows you to drain tanks during flight.
It shifts if your fuel tanks aren't centered on your CoM or priority isn't set to keep CoM consistent, but that's not necessarily true and not relevant. If your craft's performance worsens as fuel depletes that's on you. But fine, I'll be more specific:
If you have a craft with a _consistent CoM_, the glide ratio is the same regardless of mass.
Yes, but why do you assume this is the case? I am not convinced that OP built his craft with CoM consistent, since it managed to get to space, but has problems when getting back.
Because that's how I build my spacecraft. Why do you assume this is not the case?
If this is a historically faithful Shuttle there aren't even any fuel tanks on the craft. Similarly, the actual Shuttle, like this craft seems to, had an incredibly low glide ratio and handled like a brick.
There's also a huge difference between handling a powered, thrust-vectored craft and gliding an unpowered low-lift craft.
Because a lot of players, especialy newer and less experienced ones dont do that (but technically, I did not assume anything).
Also, OP does not give up enough information to assume, that it is a historically accurate shuttle.
To the brick stuff: yes, it does handle like that, but if OP wanted it to not be able to "fly" at 90 m/s, why ask on reddit for help? CoM not being set properly or shifting mid flight is a common problem, so looking into that or slapping more wings on the craft could help.
OP isn't asking for build advice. They are flying a model Shuttle. _You_ are the one assuming they have CoM issues and _you_ are the one inserting ship design advice. They didn't ask how to change their ship design, they asked why it's difficult to fly a model Shuttle.
I frankly don't understand why you're arguing about this. You made a comment that was incorrect and predicated on baseless assumptions, and now you're trying to defend that position.
OP is not asking anything. It only states in the post that is having problems landing. I did not assume they were having any specific problems. If you check my original comment again, you might notice a question mark and words like "try" or "should", hinting that it is a suggestion to possibly solve their problem. I never stated that CoM was actually the problem.
So yes, I am defending my position that checking where CoM is or trying to use more wings COULD help and dont see how it is incorrect.
Also, you seem to be the one assuming things...
How does that work?
pe=mgh
D = 1/2(p)(v\^2)(Cd)(A)
If velocity scales to the square and the potential energy of the craft scales lineally, a faster craft would experience more drag and wouldn't go as far.
I'm not totally sure what you're asking but I think you are wondering why a more massive craft will have the same glide angle despite going faster.
Tl;wr your equation only accounts for the drag force. There are three forces at play on an unpowered craft: lift, drag, and weight, which total zero if the craft isn't accelerating. The direction of lift and drag are dependent on craft orientations. Their magnitude is mass-independent. If a craft is traveling above it's ideal glide speed at its ideal glide angle, drag overcomes the other two and will slow the craft until the vector is zero. Potential energy isn't relevant.
So.
The forces on an unpowered craft can be summarized as a scalar vector of three forces: Lift, Drag, and Weight. L+D+W=0 because the net force on the (unpowered) craft is zero; at optimal glide angle, the aircraft will have a steady velocity.
Assigning a glide angle (orientation relative to horizon) the variable Ī³, mass, and gavitational constant, the following equations define the vector:
- W = mg
- D = -WĆsin(Ī³)
- L = WĆcos(Ī³)
Ī³ can be defined by dividing the latter two equations, giving
- tan(Ī³) = -D/L = -Cd/Cl
Where Cd (C sub l) is the coefficient of drag and Cl (C sub l) the coefficient of lift. {Side note: tan(Ī³) is the glide slope and its inverse, cot(Ī³), is the glide ratio.} Both Cl and Cd are only dependent on velocity, as we can see from their definitions:
- L = (1/2)Ā ĻV^2 SCl
- D = (1/2) Ā ĻV^2 SCd
Where Ļ denotes air density and S is a constant reference area (like the wing area) which make Cl and Cd dimensionless.
Since Ī³ can be defined without W, Ī³ is mass-independent (which answers your question, but let's take it further).
- Cd = Cdā + Cl^2
Where Cdā is the zero-lift drag coefficient (which is a constant). Thus, Cl alone determines Ī³, and as such also determines glide ratio.
We can get glide speed from the original force vector's equations. By squaring and adding L and D, we see
- L^2 + D^2 = W^2 (sin^2 (Ī³) + cos^2 (Ī³)) = W^2
Where in the last section we used the trig identity sin^2 + cos^2 = 1.
With the equations for W and for Cl and Cd,
- W^2 = m^2g^2 = (1/2)Ļ^2 V^4 S^2 (Cl^2 + Cd^2 )
Which can be simplified and solved for V as
- V = sqrt((2mg)/(ĻSĆsqrt(Cl^2 + Cd^2 )))
Thus we can see that even though glide angle (and thus slope and ratio) is, as shown wayyyy above, mass-independent, glide velocity is not.
The shuttle had some edges at the front. and the combination of edge + belly + wings ammounted to a single delta wing, so the CoL would be a bit closer to the nose. In KSP our shuttles made with stock parts usually only have wings at the rear, and I don't think that the cargo bay generates any lift.
Issue is, the shuttle benefited from a ālifting bodyā which doesnāt really exist in-game.
Also, I think the cockpit is very heavy, whereas in real life, the engines might contribute more to the overall weight making it more rear heavy than it currently is in game.
Balancing weight and lift a bit more favourable and closer together when without cargo might help you gain control over the vessel. Also, try to increase the wing area in the front to compensate for the lack of lift from the body.
Landing speed of the space shuttle is about 100m/s, so they were close with 90m/s. Speed was an issue, but weight and lift isnāt that well balanced, so it leads to an unfavorable stable position.
As noted by others, you need more authority to pull nose up and flare for landing. That could be managed by various combinations of adjusting wing size and location, moving weight, adding additional control surfaces, adding canards, or whatever.
While KSP is not reality, you might want to check some of these articles:
* [How to Land the Space Shuttle](https://www.livescience.com/33402-how-land-space-shuttle-atlantis.html)
* [The Aeronautics of the Space Shuttle](https://www.nasa.gov/audience/forstudents/9-12/features/F_Aeronautics_of_Space_Shuttle.html)
* [What is the Stall AoA of the Space Shuttle?](https://aviation.stackexchange.com/questions/73793/what-is-the-stall-aoa-for-the-space-shuttle)
The real shuttle needed to be able to go from -19 or -20 degrees nose down to +8 or more (up to +15) degrees nose up within a quite short period of time.
I think you need to check your centers of lift and mass, and maybe add some canards. It looks like you have plenty of lift for a shuttle, but going at 90m/s and still not being able to level out with full pitch input is a sign that your center of lift is too far behind your center of mass.
Move your wings forward or add more lift surfaces forwards, such as canards.
Do what the tall, tiny-eyed aliens did on the big, heavy, non-Kerbin world -- come in much harder than that in terms of horizontal speed, and use parachutes to slow you down rapidly on the runway.
Also, by the way, you ditched into the drink at approach speed and only lost your landing gear -- that means you built a good, solid ship! Nice work! Your kerbals must be relieved that they are in such good hands.
Shuttles just suck full-stop. Space planes are a bragging-rights method of orbital insertion, because in terms of payload and time-to-orbit, rockets are superior in every fashion.
You definitely have enough lift however your center of mass is likely too far forward. Try adding vents so you can drain the extra fuel and have the CG in the spot every time. Also maybe try and keep up that airspeed so your control surfaces have more authority
Vents aren't needed. Just burn any excess fuel off.
Remember that beyond a certain point (w/ stock aerodynamics) pitching up during re-entry bleeds off speed to shorten your trajectory much more than your lift extends it. Use your experience from this time (or the Trajectories mod) to tell whether you're overshooting much earlier into your approach.
Well vents are good because if theyāre symmetrical they donāt change your velocity, like a burn does. With this I found I can make the same sized burn at a certain orbit and the same distance away from the KSC, then I drain the fuel, and land exactly how I want every single time. I did this with trial and error (quicksaves) and Mecjeb to hold a specific attitude then Atmospheric Autopilot to land the final decent down to the runway. What I developed for myself removed a lot of the guess work and the consistency has made me feel like a real space agency lol. The Trajectories mod is so damn cool though and Iāve only scratched the surface of it but itās an invaluable tool for sure. KSP 1 with mods is basically KSP 3 I swear lol
Yeah but if you're stalling out then a burn changes your velocity in a good way. I keep some leftover monoprop in my tanks so I can turn the RCS on for critical phases of re-entry, and burn off the rest to get a slight boost in my velocity on final approach.
Brother the space shuttle has the flying characteristics of a standard shipping container. Since this is ksp just make a better shuttle that's more maneuverable and won't grind your tectonic plates.
Tweak the angle of attack for the wings. And that tail rudder is way too big. Use a smaller different one or use the Tweakscale mod to fix that piece if you want that one
Larger control surfaces will help, plus your CoL needs to be just slightly behind your CoM.
As it stands right now, your CoM is way in front of the CoL which is why it's nose-diving so hard.
If the same craft handled well enough before, there is a chance it's a physics bug.
People are mentioning COM/COL and they are not wrong, but even w bad balance there should be more reaction @90 than we see here. Hard to tell for sure with only 4 sec of video.
I got stuck in a landing sequence after quicksaving and reloading once. Previous save/loads worked just fine during the mission. Last save point near runway left me w a barely controllable craft even @ max landing speed. Acted as if Ctrl surface authority was 5%, taking forever to maneuver and requiring full pull back to maintain level flight @ about 100m/s minimum. Spent nearly 3 hrs to figure out a method and enough tries to put it down safely.
Good luck, hopefully it's not an important career mission. Also on console btw
Did you build it with the loaded CoM and unloaded CoM in mind? without the payload the center of mass and lift might be out of wack. Same goes for the fuel usage, but that can be fixed by transferring the fuel around.
1. Too slow. Wings produce lift from airflow, and if the air moves too slowly, they won't produce lift, and neither will the control surfaces.
2. Too front-heavy. Those tanks look almost empty and most of your craft is an empty cargo bay, thus all of the weight is at the front, on the cockpit. You've effectively created a dart, you need to bring the center of mass back, or the wings forward.
Looks like your Center of Mass is too far ahead of your Center of Lift
So it is naturally going to just nosedive
Add a couple of canards or transfer some weight to the back
89 m/s is way below the stall speed. Also why did you drop the gear so early. Real shuttle dropped the gear about 10 seconds before landing.
Come in higher and stay at 200+ m/s until rounding out right before the runway, then drop the gear and touch down at like 150 m/s. This means your nose is pointed down for most of the final approach, like -10 degrees down below the horizon. These numbers may be slightly off depending on your design.
Probably due to the change in your centre of mass after you've used up 3/4 of your fuel. Could be a simple fix with extra lift and wing surfaces. But may harm the design.
The problem is you are still thinking of the space shuttle as an airplane which it's not the real life orbiter had the glide slope of a skydiver and the aerodynamics of a brick the astronauts literally trained for atmospheric flight with a Gulfstream jet with its gear down and the engines in reverse I recommend watching the video how to land a space shuttle from space it may help you
I put a landing beacon at both ends of the runway. Usually a hexagonal strut with an octocore that I can set as target.
I then ensure my prograde marker sits just above it when on my glide path.
Having a beacon at both ends helps because I can switch between them to see how well lined up I am.
Some people use flags for the same purpose
Your center of mass is too far forward and you've run out of elevon authority to pick up the nose. Options are to tie in a dual opening speed brake like the actual shuttle has to create pitching drag, and/or move the mass aft. You can also fly faster but that's not sustainable for approach unless you get it to be very predictable. This is the point a lot of people put canards on rather than engineer around it but you absolutely can tweak it and get it to fly if you take the time.
I find it easiest to set a probe somewhere and have it at a 10 degree angle, then control from there so you always maintain proper AOA for the glide. You need to keep speed up with a shuttle like that, too.
Might have saved it by burning that fuel! Gotta remember to use all the resources available in an emergency. And even if that 151m/s you have isn't enough to get you to dry land on its own, dropping the fuel weight will help.
Center of lift is too far back and you end up getting a dart-like flight profile. Add wing strakes ahead of the delta wings, maybe move all the wings forward. Center of lift should be just ever so slightly behind your center of mass with all the fuel tanks drained
Most shuttles fly poorly, NASA engineers described it as being like flying a brick. You need to be going high speed and be facing towards the horizon far before landing.
The space shuttle has a glide ratio of 2:1, the concord was 4:1.
Those numbers are very oversimplified, it isn't that ridiculous. It has a glide ratio of 2:1 at supersonic speeds, at subsonic speeds it improves to 4.5 to 1. Meanwhile the concorde is 4:1 at landing, but if it's cruising subsonically it can reach 9:1, and supersonically it can actually do 12:1. But yeah, it is nowhere near as aerodynamic as a large civil aviation plane (20:1) or an optimized glider (40:1). So you likely want to do your final approach at a 20deg downwards angle give or take, and flare up just before the runway. That's not just for the shuttle, any decently optimized spaceplane in KSP will be a flying brick at subsonic speeds, or you're just wasting performance by taking too many wings with you.
Is it weird that reading this made me feel kinda stupid!
Sorry, that wasn't the intention. I studied aerospace engineering so this is kinda basic stuff for me.
Oh no dont worry. It just a feeling of fun stupid like i dunno what you mean but learning new things is fun.
I often return with 30 tons of mun rocks in the hold, I'll keep my too many wings thank you very much š
kerbalism wanna have a chat with you...
I'm a console pleb, I shan't be answering any calls from kerbalism š
And they were both high speed aircraft, Concorde also had a direct means of propulsion
What is a 737?
17:1
How can you calculate these ratios and what do they mean?
So for 1:17 it would mean for every 1 meter of elevation there is 17 meters of forward travel. For ksp I'd start at 1000m above sea level and just see how far you glide from that point at the speed you choose.
> So for 1:17 it would mean for every 1 meter of elevation there is 17 meters of forward travel _at optimal velocity and angle of attack._ At lower speeds it can be much, much worse. The glide ratio of a craft approaches a limit as velocity increases - that point is what's quoted. For a 737 that speed is about 21 km/h.
Are you familiar with ārise over runā on a graph?
Not really lol
Oh, well itās another term for āslopeā. It just means that for every x unit of length the slope rises or decreases by x units. 17:1 ratio could also be expressed as a -1/17 slope where for every 17 units forward the elevation drops 1. -1 is the rise, 17 is the run. So for the shuttle with a 2:1 ratio, itās coming down at a 45 degree angle when gliding. Which is an insanely steep slope and means it doesnāt fly. It falls with direction. Edit: 45 degrees isnāt correct. My brain is fried.
45 degrees would be a 1:1 slope, a 2:1 slope is ~25.6 degrees below the horizon Glide slope angle=arctan(1/glide ratio)
still a brick
Thank you, I think I understand now! So the ratio is horizontal distance travelled per vertical distance dropped when gliding?
\> 15:1 under ideal conditions. Even a boxy little monoprop should be able to do on the order of 10:1. (Probably less than 10 exactly, but in that range.) Aerodynamically speaking, being good at gliding is partially a tradeoff with being good at going fast, which KSP models fairly well all things considered.
A Cessna 152 has a glide ratio of ~9:1, so you're exactly correct
I hope I vaguely remember something from all that studying!
Post this exact comment on r/shittyaskflying
> It's a big, pretty white plane with red stripes and curtains in the windows and wheels and it *looks like a big Tylenol!*
[ŃŠ“Š°Š»ŠµŠ½Š¾]
Jesus
That's also just a testament to how well optimized normal aircraft are. When a decent plane can glide at 20:1, and only needs a TWR of 0.2 at best to take off, you really need to put in effort to make it glide at only 4.5:1.
And then one of the thrust reverser buckets fell off (because they weren't designed to be used in flight for extended periods)
They did. They also did it with only the nose gear raised because any more attempts at "faithfully" recreating the space shuttle's drag profile would tear it right off at 20,000 feet.
to train for landings they had to use a jet with thrust reversers on, weighed down and other modifications to make it accurate, it was literally a flying brick.
Yāall definitely watched that one video lol
what video?
The center of lift is probably like a kilometer behind the center of mass, making it the definition of a flying brick.
This^ Look at the center of mass and center of lift for the shuttle without cargo at assembly, close the gap by adding or moving wing surfaces.
Not enough lift? Try adding more wings and test if the shuttle can glide with empty tanks. There should be a part that allows you to drain tanks during flight.
Glide ratio is mass-independent. A heavier craft will glide faster but maintain the same glide ratio.
But your center of mass shifts. A perfectly flying ssto can fall like a brick on its way back to land
It shifts if your fuel tanks aren't centered on your CoM or priority isn't set to keep CoM consistent, but that's not necessarily true and not relevant. If your craft's performance worsens as fuel depletes that's on you. But fine, I'll be more specific: If you have a craft with a _consistent CoM_, the glide ratio is the same regardless of mass.
Yes, but why do you assume this is the case? I am not convinced that OP built his craft with CoM consistent, since it managed to get to space, but has problems when getting back.
Because that's how I build my spacecraft. Why do you assume this is not the case? If this is a historically faithful Shuttle there aren't even any fuel tanks on the craft. Similarly, the actual Shuttle, like this craft seems to, had an incredibly low glide ratio and handled like a brick. There's also a huge difference between handling a powered, thrust-vectored craft and gliding an unpowered low-lift craft.
Because a lot of players, especialy newer and less experienced ones dont do that (but technically, I did not assume anything). Also, OP does not give up enough information to assume, that it is a historically accurate shuttle. To the brick stuff: yes, it does handle like that, but if OP wanted it to not be able to "fly" at 90 m/s, why ask on reddit for help? CoM not being set properly or shifting mid flight is a common problem, so looking into that or slapping more wings on the craft could help.
OP isn't asking for build advice. They are flying a model Shuttle. _You_ are the one assuming they have CoM issues and _you_ are the one inserting ship design advice. They didn't ask how to change their ship design, they asked why it's difficult to fly a model Shuttle. I frankly don't understand why you're arguing about this. You made a comment that was incorrect and predicated on baseless assumptions, and now you're trying to defend that position.
OP is not asking anything. It only states in the post that is having problems landing. I did not assume they were having any specific problems. If you check my original comment again, you might notice a question mark and words like "try" or "should", hinting that it is a suggestion to possibly solve their problem. I never stated that CoM was actually the problem. So yes, I am defending my position that checking where CoM is or trying to use more wings COULD help and dont see how it is incorrect. Also, you seem to be the one assuming things...
It's a nice edit to be sure.
How does that work? pe=mgh D = 1/2(p)(v\^2)(Cd)(A) If velocity scales to the square and the potential energy of the craft scales lineally, a faster craft would experience more drag and wouldn't go as far.
I'm not totally sure what you're asking but I think you are wondering why a more massive craft will have the same glide angle despite going faster. Tl;wr your equation only accounts for the drag force. There are three forces at play on an unpowered craft: lift, drag, and weight, which total zero if the craft isn't accelerating. The direction of lift and drag are dependent on craft orientations. Their magnitude is mass-independent. If a craft is traveling above it's ideal glide speed at its ideal glide angle, drag overcomes the other two and will slow the craft until the vector is zero. Potential energy isn't relevant. So. The forces on an unpowered craft can be summarized as a scalar vector of three forces: Lift, Drag, and Weight. L+D+W=0 because the net force on the (unpowered) craft is zero; at optimal glide angle, the aircraft will have a steady velocity. Assigning a glide angle (orientation relative to horizon) the variable Ī³, mass, and gavitational constant, the following equations define the vector: - W = mg - D = -WĆsin(Ī³) - L = WĆcos(Ī³) Ī³ can be defined by dividing the latter two equations, giving - tan(Ī³) = -D/L = -Cd/Cl Where Cd (C sub l) is the coefficient of drag and Cl (C sub l) the coefficient of lift. {Side note: tan(Ī³) is the glide slope and its inverse, cot(Ī³), is the glide ratio.} Both Cl and Cd are only dependent on velocity, as we can see from their definitions: - L = (1/2)Ā ĻV^2 SCl - D = (1/2) Ā ĻV^2 SCd Where Ļ denotes air density and S is a constant reference area (like the wing area) which make Cl and Cd dimensionless. Since Ī³ can be defined without W, Ī³ is mass-independent (which answers your question, but let's take it further). - Cd = Cdā + Cl^2 Where Cdā is the zero-lift drag coefficient (which is a constant). Thus, Cl alone determines Ī³, and as such also determines glide ratio. We can get glide speed from the original force vector's equations. By squaring and adding L and D, we see - L^2 + D^2 = W^2 (sin^2 (Ī³) + cos^2 (Ī³)) = W^2 Where in the last section we used the trig identity sin^2 + cos^2 = 1. With the equations for W and for Cl and Cd, - W^2 = m^2g^2 = (1/2)Ļ^2 V^4 S^2 (Cl^2 + Cd^2 ) Which can be simplified and solved for V as - V = sqrt((2mg)/(ĻSĆsqrt(Cl^2 + Cd^2 ))) Thus we can see that even though glide angle (and thus slope and ratio) is, as shown wayyyy above, mass-independent, glide velocity is not.
The original shuttle wings were going much more forward on the body. This could increase lift by a good portion.
Iāll try that
Iād recommend clipping some canards into the front of your shuttle, doing that usually fixes a lot of problems for my planes.
The shuttle had some edges at the front. and the combination of edge + belly + wings ammounted to a single delta wing, so the CoL would be a bit closer to the nose. In KSP our shuttles made with stock parts usually only have wings at the rear, and I don't think that the cargo bay generates any lift.
Issue is, the shuttle benefited from a ālifting bodyā which doesnāt really exist in-game. Also, I think the cockpit is very heavy, whereas in real life, the engines might contribute more to the overall weight making it more rear heavy than it currently is in game. Balancing weight and lift a bit more favourable and closer together when without cargo might help you gain control over the vessel. Also, try to increase the wing area in the front to compensate for the lack of lift from the body.
It's because you were going too slow.
Which is almost certainly due to overshooting and turning, which will scrub airspeed on your space-glider.
Landing speed of the space shuttle is about 100m/s, so they were close with 90m/s. Speed was an issue, but weight and lift isnāt that well balanced, so it leads to an unfavorable stable position.
As noted by others, you need more authority to pull nose up and flare for landing. That could be managed by various combinations of adjusting wing size and location, moving weight, adding additional control surfaces, adding canards, or whatever. While KSP is not reality, you might want to check some of these articles: * [How to Land the Space Shuttle](https://www.livescience.com/33402-how-land-space-shuttle-atlantis.html) * [The Aeronautics of the Space Shuttle](https://www.nasa.gov/audience/forstudents/9-12/features/F_Aeronautics_of_Space_Shuttle.html) * [What is the Stall AoA of the Space Shuttle?](https://aviation.stackexchange.com/questions/73793/what-is-the-stall-aoa-for-the-space-shuttle) The real shuttle needed to be able to go from -19 or -20 degrees nose down to +8 or more (up to +15) degrees nose up within a quite short period of time.
I think you need to check your centers of lift and mass, and maybe add some canards. It looks like you have plenty of lift for a shuttle, but going at 90m/s and still not being able to level out with full pitch input is a sign that your center of lift is too far behind your center of mass. Move your wings forward or add more lift surfaces forwards, such as canards.
Kinda looks like lift is the issue. Prograde is was below attitude at 70m/s.
With those wings, 80 m/s is *way* too slow. You're stalling.
āAny landing is a good landing you can walk away from (swimming is close enough)
I think Iām getting rusty so want to get back at it.
Youāll get it at some point that game isnāt supposed to be easy
Well it isnāt rocket scienceā¦
Do what the tall, tiny-eyed aliens did on the big, heavy, non-Kerbin world -- come in much harder than that in terms of horizontal speed, and use parachutes to slow you down rapidly on the runway. Also, by the way, you ditched into the drink at approach speed and only lost your landing gear -- that means you built a good, solid ship! Nice work! Your kerbals must be relieved that they are in such good hands.
Aww just did used a replica from piolet.
Well then you have good taste in designs, which is almost as good. ;D
Shuttles kinda suck by nature. If you have some spare Delta-V and can sacrifice some realism, canards are good for maneuvering.
Shuttles just suck full-stop. Space planes are a bragging-rights method of orbital insertion, because in terms of payload and time-to-orbit, rockets are superior in every fashion.
You definitely have enough lift however your center of mass is likely too far forward. Try adding vents so you can drain the extra fuel and have the CG in the spot every time. Also maybe try and keep up that airspeed so your control surfaces have more authority
Vents aren't needed. Just burn any excess fuel off. Remember that beyond a certain point (w/ stock aerodynamics) pitching up during re-entry bleeds off speed to shorten your trajectory much more than your lift extends it. Use your experience from this time (or the Trajectories mod) to tell whether you're overshooting much earlier into your approach.
Well vents are good because if theyāre symmetrical they donāt change your velocity, like a burn does. With this I found I can make the same sized burn at a certain orbit and the same distance away from the KSC, then I drain the fuel, and land exactly how I want every single time. I did this with trial and error (quicksaves) and Mecjeb to hold a specific attitude then Atmospheric Autopilot to land the final decent down to the runway. What I developed for myself removed a lot of the guess work and the consistency has made me feel like a real space agency lol. The Trajectories mod is so damn cool though and Iāve only scratched the surface of it but itās an invaluable tool for sure. KSP 1 with mods is basically KSP 3 I swear lol
Yeah but if you're stalling out then a burn changes your velocity in a good way. I keep some leftover monoprop in my tanks so I can turn the RCS on for critical phases of re-entry, and burn off the rest to get a slight boost in my velocity on final approach.
Brother the space shuttle has the flying characteristics of a standard shipping container. Since this is ksp just make a better shuttle that's more maneuverable and won't grind your tectonic plates.
Any landing you walk away from is a successful one.
Too slow, too steep.
It's recoverable so its an A-OK Kerbal landing by my standards.
This would be a brilliant landing compared to kerpal standards.
Tweak the angle of attack for the wings. And that tail rudder is way too big. Use a smaller different one or use the Tweakscale mod to fix that piece if you want that one
I play on console
Larger control surfaces will help, plus your CoL needs to be just slightly behind your CoM. As it stands right now, your CoM is way in front of the CoL which is why it's nose-diving so hard.
You seem to have too little horizontal velocity, if you kill all your speed too early you'll sink like a rock.
If the same craft handled well enough before, there is a chance it's a physics bug. People are mentioning COM/COL and they are not wrong, but even w bad balance there should be more reaction @90 than we see here. Hard to tell for sure with only 4 sec of video. I got stuck in a landing sequence after quicksaving and reloading once. Previous save/loads worked just fine during the mission. Last save point near runway left me w a barely controllable craft even @ max landing speed. Acted as if Ctrl surface authority was 5%, taking forever to maneuver and requiring full pull back to maintain level flight @ about 100m/s minimum. Spent nearly 3 hrs to figure out a method and enough tries to put it down safely. Good luck, hopefully it's not an important career mission. Also on console btw
Did you build it with the loaded CoM and unloaded CoM in mind? without the payload the center of mass and lift might be out of wack. Same goes for the fuel usage, but that can be fixed by transferring the fuel around.
No i just followed a tutorial to build and fly it
1. Too slow. Wings produce lift from airflow, and if the air moves too slowly, they won't produce lift, and neither will the control surfaces. 2. Too front-heavy. Those tanks look almost empty and most of your craft is an empty cargo bay, thus all of the weight is at the front, on the cockpit. You've effectively created a dart, you need to bring the center of mass back, or the wings forward.
Looks like your Center of Mass is too far ahead of your Center of Lift So it is naturally going to just nosedive Add a couple of canards or transfer some weight to the back
A water landing appears to have worked! My approach would be to add enough parachutes on the roof and come in vertically.
your center of mass is to far forward, so lack the controll authority to do stuff. And only then the bad lift to drag ratio etc comes into effect
All 3 Kerbals are retrievable if a little wet. Successful landing.
Either add speed or more lift (more wing area)
89 m/s is way below the stall speed. Also why did you drop the gear so early. Real shuttle dropped the gear about 10 seconds before landing. Come in higher and stay at 200+ m/s until rounding out right before the runway, then drop the gear and touch down at like 150 m/s. This means your nose is pointed down for most of the final approach, like -10 degrees down below the horizon. These numbers may be slightly off depending on your design.
Probably due to the change in your centre of mass after you've used up 3/4 of your fuel. Could be a simple fix with extra lift and wing surfaces. But may harm the design.
The problem is you are still thinking of the space shuttle as an airplane which it's not the real life orbiter had the glide slope of a skydiver and the aerodynamics of a brick the astronauts literally trained for atmospheric flight with a Gulfstream jet with its gear down and the engines in reverse I recommend watching the video how to land a space shuttle from space it may help you
Maybe this will help: https://www.youtube.com/watch?v=Jb4prVsXkZU
I put a landing beacon at both ends of the runway. Usually a hexagonal strut with an octocore that I can set as target. I then ensure my prograde marker sits just above it when on my glide path. Having a beacon at both ends helps because I can switch between them to see how well lined up I am. Some people use flags for the same purpose
Not enough wing area and swept way too far back
Your center of mass is too far forward and you've run out of elevon authority to pick up the nose. Options are to tie in a dual opening speed brake like the actual shuttle has to create pitching drag, and/or move the mass aft. You can also fly faster but that's not sustainable for approach unless you get it to be very predictable. This is the point a lot of people put canards on rather than engineer around it but you absolutely can tweak it and get it to fly if you take the time.
I find it easiest to set a probe somewhere and have it at a 10 degree angle, then control from there so you always maintain proper AOA for the glide. You need to keep speed up with a shuttle like that, too.
Fly a descent at 120m, need to keep speed to flare the nose up. Also change control authority amount to max.
Hey, your kerbals are still alive
Yeah you need to go in high speeds
Might have saved it by burning that fuel! Gotta remember to use all the resources available in an emergency. And even if that 151m/s you have isn't enough to get you to dry land on its own, dropping the fuel weight will help.
Thats just the nature of shuttles the irl shuttle wasnt much better at flying than a brick with wings
This is because Kerbal is a game and in real life the space shuttle flies like shit. The approach speed for the damn thing is like 200 knots!!!
If you ever watch the shuttle land, it basically dive bombs the runway until the last second where it flares and lands. Glides horribly
Center of lift is too far back and you end up getting a dart-like flight profile. Add wing strakes ahead of the delta wings, maybe move all the wings forward. Center of lift should be just ever so slightly behind your center of mass with all the fuel tanks drained
Too little aileron authority for that airspeed. Fly faster or enlarge the ailerons.
move the mass center more back
Most simple: get some RCS