Tips on landing SSTO's B9, NEAR.

[Secuas]

Hey I recently made an 2.5m cargo SSTO and it can just barely make it into a 200x200 orbit. I still fly like i use stock aero. Anyone got any tips on how I can burn/fly more efficient? I use B9 and NEAR.(and a ton more but those are irrelavant)

Thanks in advance!

Edited November 24, 2014 by Kaname

[RainDreamer]

Can we get image of the SSTO? And what is your flight profile like?

Usually I try to extend my atmospheric flight a bit to get closer to orbital speed before switching to close cycle mode to save fuel. Close cycle mode on SABREs burns fuel like crazy, so the more horizontal momentum I get before going to orbital height, the more fuel I save from not doing the same horizontal burn in outerspace where the engine eats much more fuel. But it varies between crafts, so I can't say exactly how long you should do it or at what altitude.

[Secuas]

Here is an album of my great SSTO the HCL-02 Fox. It has a Skylon like engine setup and carried one Rockomax jumbo-64 to orbit. (with using a tiny tad of oxidizer of it due to bad flying)

I just tried another aproah on flying wich got me above 30.000m with still using jet engines.

http://imgur.com/a/9mixg#0

[RainDreamer]

So here is just blind guessing, but do you have any difficulty controlling pitch during atmospheric flight? Is it difficult to lift the nose up during nose dive?

[Secuas]

Yes, when it hits the the atmosphere it picthes down again and burns up (r.i.p. kerbals)

Help is being apriciated because all my kerbals are dying.

Edited November 24, 2014 by Kaname

[RainDreamer]

I am no expert in space plane design, but I think the problem is because of the lack of control surfaces. Some small winglets, or even stabilators before the front wings might help a bit more here. Also, the parts behind the two main wings seems to be fixed trailing edges and not control surfaces - they gives better aerodynamic profile but not particularly useful in controlling the plane directly (as far as I know).

If aesthetic/size/space is a problem and you don't want to put winglets at the front, you can try making the wingspan longer and adding a lot more control surfaces.

I hope someone with more experience than me can come in, I am interested in this too.

[Wanderfound]

Pics of the ship misbehaving and dying would be useful. At what altitude do you lose control? What happens when you try to pull the nose up? How steeply are you reentering? Etc.

It may be a lack of sufficient high speed pitch authority, but it's just as likely to be a piloting issue.

I did a tutorial recently that you should find helpful, covering spaceplane construction, ascent, reentry and landing. It was intended for FAR, but NEAR is close enough not to matter too much.

See http://s1378.photobucket.com/user/craigmotbey/Kerbal/Tutorials/Hangar%20to%20Landing/story

You may also find the tips here useful: http://forum.kerbalspaceprogram.com/threads/90747-Kerbodyne-SSTO-Division-Omnibus-Thread?p=1353890&viewfull=1#post1353890

[Hodo]

In NEAR it is a bit harder to perform re-entry because of the lack of mach affects to slow the craft down. FAR you have additional aerodynamic forces on a craft to slow it down naturally.

But the biggest suggestion is look at your empty CoM vs CoL. I am probably guessing it has moved a fair bit back towards the rear of the craft, and placing it behind your CoL at that point.

In the SPH building, click on each on of your tanks and empty them completely to see where your CoM shifts to. Or you can down load the RCS build aid, which is the best tool I have ever downloaded.

[Secuas]

Hey Wanderfound, I just finished getting all these screenshots for you. I call it: Landing, an aerobraking story. http://imgur.com/a/L9aWu#15 My apologies they are not in the right order.

It starts off good keeping a 45 degree pitch then as I get deeper in the upper atmosphere, RCS helps fighting the drag and with the second RCS can't hold it anymore. It spins out of controll and aerobrakes over and over and over again. I really hope we can figure out what is causing this. (Also I tried pumping all the fuel into the back of the plane.)

Am I that bad of a pilot or a puny design flaw?

Thanks in Advance.

Edited November 24, 2014 by Kaname
Dem typo's

[Taki117]

Hey Wanderfound, I just finished getting all these screenshots for you. I call it: Landing, an aerobraking story. http://imgur.com/a/L9aWu#15 My apologies they are not in the right order.

It starts off good keeping a 45 degree pitch then as I get deeper in the upper atmosphere, RCS helps fighting the drag and with the second RCS can't hold it anymore. It spins out of controll and aerobrakes over and over and over again. I really hope we can figure out what is causing this. (Also I tried pumping all the fuel into the back of the plane.)

Am I that bad of a pilot or a puny design flaw?

Thanks in Advance.

You have Air brakes! Use them! No seriously, they will help you slow down during Reentry, also don't try to hold 45 through the entire reentry, just until the aircraft naturally wants to pitch over, then let it. at that point aerodynamics are going to take over and you will fly pretty good, also you want to pump your fuel FORWARDS so that your CoM is in front of (or on top of) your CoL, this will add to your stability. You might also consider adding Airbrakes to the sides of the fuselage under your tail so that your Center of Pressure moves to the back of your aircraft, which will keep it more stable during reentry.

[Voculus]

Hey Kaname, I mentioned this in the PM earlier, but the simplest thing you can try is letting the MJ SAS keep you pointed prograde, and open up those speed brakes! Pitching the ship up sharply to present the flat underbelly to the wind only works at very high altitudes, and will cause you problems as you get lower, as you've found out.

Let that beast plow straight in! Into the wind, not the ground!

[Secuas]

Thanks again for all the support I'm getting I am testing a lot to learn how this works... I have to land this thing safely this week...

Btw plowing right in won't help... I disintegrated... I use DRE aswell... (r.i.p. kerbals again.)

Edited November 24, 2014 by Kaname

[RainDreamer]

Usually I try to keep my plane stable when I am hitting dense atmosphere around 35km until I reach about 10km and below before pulling maneuvers. Otherwise I would be thrown out of control quickly with the speed I am falling. Once I hit the below 10km mark and properly slowed down, I can pretty much glide the whole way down with ease.

[Wanderfound]

Thanks again for all the support I'm getting I am testing a lot to learn how this works... I have to land this thing safely this week...

Btw plowing right in won't help... I disintegrated... I use DRE aswell... (r.i.p. kerbals again.)

Exactly what is possible depends upon the design, but as general guidelines:

* High AoA (i.e. 40° or so) in the upper atmosphere, but stop as soon as you start to feel the atmosphere through your controls.

* Moderate AoA (i.e. about 10°) to level off. Aim to have the plane flying level by 30,000m.

DaMichel's Kerbal Flight Data is very useful for this. Steepen your AoA as soon as the temperature warning goes yellow; try to keep it out of the red.

[prophet_01]

Judging from the pics I guess that the craft has most of the fuel stored in the tail section. If that is the case, I would expect the CoG to move a lot. If it gets too far in front of your CoL or maybe too close the plane might flip. It's hard to tell without the CoM/CoL, so sry for the wipd guessing. You can test this in the SPH.

Do you have airbreaks? Placing them near the tail in symetry should help with stabilising during reentry and also offers you the possibilty to control your speed more effectively.put em on an action group.

Also, I noticed that your plane seems to have roll issues (I guess due to sideslip). If you put your wings lower at the main body and make the face slightly upwards you could fix a number of issues. Look at fighter jets or the space shuttle, theire outer wing edges (where you placed the sabres) are facing slightly upwards (your sabres would need to be moved a little bit up or down to make it fly straight). If you look at it from the front it would look like a " v " (more shallow but you should get the idea.

I've build and landed a number of small, big and huge shuttles (my ssto's fail to reach orbit with far and b9 ). Getting back to the runway is the easyer part in my experience^^

[Wanderfound]

BTW, the easy fix: lose NEAR, install FAR. Then run some analysis screens and post them here; we'll be able to tell you exactly what's wrong.

Despite perceptions, NEAR is actually harder than FAR. Simpler != easier.

[Secuas]

Nothing seems to help anymore the atmosphere really forces it downwards I can do nothing to fight that. Brakes dont seem to help either. It just points down too much and everything burns up.

[RainDreamer]

Have you tried to fire the engine and use the engine gimbal to help you pitch up? Just do it in short bursts. This really sounds like my first attempt at huge space plane too...

I think the plane need some redesign. More brakes, more control surfaces, account for moving COM, etc. But if you want to salvage this thing, it is going to be difficult.

Edited November 24, 2014 by RainDreamer

[Wanderfound]

Nothing seems to help anymore the atmosphere really forces it downwards I can do nothing to fight that. Brakes dont seem to help either. It just points down too much and everything burns up.

This suggests insufficient pitch authority.

One possibly relevant note: at hypersonic speeds, rearset conventional control surfaces lose much of their power. The wind is skipping past the top of the wing too quickly to notice the elevators.

This is where all-moving control surfaces (e.g. canards, AV-R8's) come into their own. Some all-moving forward-set elevators (i.e. canards, in the real-world rather than KSP definition) will give you a lot more hypersonic pitch authority.

You'll need to adjust your wings rearwards to compensate, though. Too much forward lift = very bad.

If you hold maximum pitch up (i.e. hold down the S key) throughout, what happens?

[Secuas]

The same thing happens when I mash 'S'. It levels out at about 5 degrees pitch and burns up. Maybe I should also mention I de-orbit from a 200x200 orbit. 200x200 is my "default altitude". Can this be a factor since it may have greater speed in the first place?

I don't feel like burning up and dying in the atmosphere again.

Edited November 24, 2014 by Kaname

[Wanderfound]

The same thing happens when I mash 'S'. It levels out at about 5 degrees pitch and burns up. Maybe I should also mention I de-orbit from a 200x200 orbit. 200x200 is my "default altitude". Can this be a factor since it may have greater speed in the first place?

It doesn't help.

You can deorbit a spaceplane direct from interplanetary if you do it right, but if you're already struggling it's worthwhile starting from the easiest spot possible. Begin in a 70x70 orbit, and drop your periapsis as little as possible (about 25km is good). Don't worry about reaching KSC for now, just try and make it alive to sea level.

Your primary job during reentry is to level off; once that's done, you're in control of your own fate. If you can't level off, you're essentially just reentering in a very poorly shielded capsule.

Edited November 24, 2014 by Wanderfound

[Voculus]

The same thing happens when I mash 'S'. It levels out at about 5 degrees pitch and burns up. Maybe I should also mention I de-orbit from a 200x200 orbit. 200x200 is my "default altitude". Can this be a factor since it may have greater speed in the first place?

I didn't realize you were using DRE, as well. My advice is crap, in that case. Wanderfound makes a good point about FAR vs NEAR, and I agree. If you're ditching the stock aero, then you should go full tilt boogie into FAR. The higher fidelity flight model will be more of a help, than a hinderance.

As far as the orbit, diving in from 200km will make for quite the aggressive decent. You may have a much easier time of it, coming in from a 100km orbit.

[Secuas]

I tried the suggestion... It just aerobrakes and orbits again. Over and over again and again. <insert refrence here>

Secondly as FAR is concerned, I tried the flight assitance it doesn't work and floops up my what Voculus called "Rocket Mojo" XD. With NEAR it's less. And with FAR I feel the only way I can safely go is forward up and down.

Edited November 24, 2014 by Kaname

[RainDreamer]

In the worst case scenario that the space plane is completely incapable of re-entry and you want to salvage the plane still, you can use KAS and do it the kerbal way: attach a bunch of chutes on it! They may burn, but they may slow your craft enough that you can survive atmospheric entry.

On an unrelated note:

If you're ditching the stock aero, then you should go full tilt boogie into FAR.

Is FAR any more memory intensive than NEAR? I want to graduate to FAR after getting the hang of aerodynamic with NEAR, but I am hitting the limit with mods here.

[Taki117]

can we get the craft file? I'd like to test out this design and see if I can identify the problem from actually flying it, as well as make some changes to see if the problem can be fixed. (You might also want to include a list of mods used in construction)