Proper Use of Airbrakes

[Cpt Kerbalkrunch]

Never used airbrakes really, because I've thus far stuck to rockets and only dabble a bit with aircraft (my ssto is just that; it goes to orbit and comes back cuz it's out of fuel). However, I'm going back to Eve, and this time I wanna do it without needing to drill and refuel. I also refuse to send a one-Kerbal ship anywhere, so it's going to be larger than it needs to be.

I'll go with understatement and say that atmospheric entry on Eve is tough. Big ships tend to flip. Been working on my lander (shield placement and whatnot), but I wanna try to make use of airbrakes. Was messing around and noticed that once the controls are engaged, the individual panel will extend when needed to adjust course. I had no idea (as I said, I haven't used them). I thought you deployed them and they twisted and turned to adjust course.

So, is this the proper way to use them? Just engage the controls and let them work? Guess I could just test it and see, but I'm testing a lot of different landers, and it's taking up a ton of time.

Thanks.

Edited April 20, 2017 by Cpt Kerbalkrunch

[FullMetalMachinist]

5 minutes ago, Cpt Kerbalkrunch said:

So, is this the proper way to use them?

It depends on what you want to use them for. They act a little like wing control surfaces. You can have them respond to control input or not, or just deploy them and have them create lots of drag. Or a combination of both. 

I would put something together and use the set orbit function to put it above Eve, then play around with it and see what works. 

[Cpt Kerbalkrunch]

4 hours ago, FullMetalMachinist said:

I would put something together and use the set orbit function to put it above Eve, then play around with it and see what works. 

Sounds about right. The trial and error method is my go-to approach anyway.

 

Thought I hit send on this a few hours ago. I guess not. Thanks for the reply.

[FancyMouse]

I only use airbrakes when I'm <1.2km/s or so. Above that it's too easy to blow up by heat. On Eve it will just explode before it can even produce noticeable drag...

unless you accept somewhat cheaty way - because (stock) drag and heat use different algorithm to calculate, you could place airbrakes so that they have drag but no heat. It is possible with stock drag/heat model.

[Razorforce7]

I really don't see their value on spaceplanes. When you build spaceplanes the proper way like many on this forum do you use the whole body of your spaceplane including your elevons as an airbrake by facing the incoming air on a pitched up attitude (like the spaceshuttle)
So you basically want to keep the nose high relative to the horizon (as much as possible for the greatest stopping power)
With the proper heat tolerant parts this should work everywhere (also on Eve)
This decceleration method works both by aerobraking and when you want to deccelerate at lower altitudes. Although don't be to aggressive on lower altitudes or your plane might brake apart. Airbrakes are good to quikly deccelerate when your flying in a straight line. However, it would be useless to you, because in ksp you won't give a rats butt to slow down more quikly in a straight line. Unless it's a way for you to show off.

They can be usefull when guiding rockets back to land when your center of mass is to far near the top. Or the top of your stage is aerodynamicaly susceptible to tumble face down into the ground. Airbrakes at the top will keep the engine parts down and allow you to steer the body somewhat to have a little guidance.
If your rocket want to tumble during descent it will likely happen high up in the atmosphere, which is the part where your airbrakes will melt. So it will only fullfill this function if you manage to get to the lower atmosphere.

They won't be very good at simulating grid fins either. Although that might be better explained due to the hard management to guide pitch and yaw control of a cillindrical stage. Something that is very hard to do in real life and requires computers in order to hit a barge at sea.

That^ is a landing accuracy challenge that cannot be fullfiled routinely through player repetition (Although I'm sure you'll be successfull atleast once if you try long enough)
With the inability to land that accurate it's far better to use a parachute (1 part) and land under engine thrust. Logical right? if all you wanna do is hit land.

I think Airbrakes is a design choice. I mean, let's be honest, they look good. And sure, they can be usefull in the lower atmosphere. But essentially all it simulates is semi controllable spoiler. That could aswell be a Big-S Elevon control surface that is inverted and extended as a spoiler. Which has more surface area then a airbrake, and can be used for alot more purposes and creates probably as much drag as a series of airbrakes. Airbrakes do give more drag individually, but more elevons do the same. Elevons do give more lift, and more drag when not extended. But they are part of your planes wing surfaces to begin with. So you'd have them on your spaceplane regardless. Again, my question, why add more airbrakes to them?
So having control surfaces on my spaceplanes I see no reason to add any airbrakes to them. Only if it is a rocket I would think about it. And only on some specific stage designs.

My final conclusion is that you can create the aerodynamic stability and stopping power without airbrakes at all. I would even recommend to never combine spaceplanes and aibrakes. They cause more limitations then usefull applications.
Oh, I'm just one man. I'm sure I left out alternative method(s) for the aibrakes. I like to hear about them.



 

[Cpt Kerbalkrunch]

3 hours ago, Razorforce7 said:

That could as well be a Big-S Elevon control surface that is inverted and extended as a spoiler. Which has more surface area then a airbrake, 

So having control surfaces on my spaceplanes I see no reason to add any airbrakes to them. Only if it is a rocket I would think about it.



 

Good post. Lot of info there. I probably wasn't as clear as I should've been in my op. It's a rocket I'm using. I only mentioned spaceplanes to highlight my inexperience with all things plane-related. I was trying different things, and when I saw the airbrake panel swing out on its own, I thought it was cool and wondered if it could help keep a rocket upright on the Eve descent. I didn't check the heat tolerance, though. Which I should've, obviously. Pretty much everything burns up on Eve.

I'm intrigued by your idea of elevons, though. I know you meant on a spaceplane, but I think maybe their control ability and higher heat tolerance might help me.

Last time, no matter which end I put the inflatable shield, it would flip the other way (and regular shields just blew up). I finally changed my design and staged outwards instead of upward. The ship was short and fat, so there was nothing to catch the air above the shield to create drag. It worked, but I don't wanna give in this time. I'll keep trying.

[Razorforce7]

@Cpt KerbalkrunchYeah, lots of info because I thought you wanted to know all possible uses of the airbrakes. I'm sure there are more still.
Like I said, airbrakes work well for descending rocket stages upright and controlled. But only in the lower atmosphere. But you could use drogue chutes for that aswell, which I do because aibrakes is usually more parts.

What I can't tell from your post is whether your stuck at aerobraking and want help or want information about airbrakes? You say you have trouble at eve, but your specific question is about airbrakes.
Does your vessel survive re-entry or not, with or without airbrakes? If not, do you neccessarily want to do it with airbrakes? I think airbrakes and Eve don't go well together, some might disagree.

You say your vessel flips upside down. You have a heatshield only on one end? If yes, that side will have the most drag so the unshielded side will tumble in the wind. Especially if it is the inflatable one

If you still got questions, screenshots will help alot more then the white of my forum background
EDIT: I won't use elevons if it is a rocket, only on spaceplanes. It is the combined use of having wings + control surfaces that make it effective for spaceplanes. Elevon's by themselves on a rocket stage will do far worse then airbrakes.

Edited April 21, 2017 by Razorforce7

[Foxster]

Using air-brakes for Eve entry is an excellent idea and often used by aficionados of the purple one. 

They keep your craft into the wind when you use a big draggy heat-shield out front. Otherwise there's a pretty good chance of flippiness and OMG-my-crew-just-melted-ness.

The way I use them is to stick quite a few (up to 16 or so sometimes) right at the back of the craft on decouplers so I can dump them before lifting. The sneaky bit is to make sure that when they are deployed they are within the cylinder of occlusion coming up from the circumference of the heat-shield.  That way they produce drag but don't burn up. If you think is in some way cheaty then just think of them being in the turbulent air behind the craft but not in the main blast of atmos.  

You can leave then deployed all the way down to assist your 'chutes. 

PS - Regarding your thoughts of a multi-crew lander: I really wouldn't. Eve is a big step up from landing&lifting anywhere else. Adding extra crew accommodation (or any extra kg of mass in general) will make your craft size/mass balloon. Do it successfully at least once with one man and go on from there. 

 

Edited April 21, 2017 by Foxster

[Spricigo]

7 minutes ago, Foxster said:

PS - Regarding your thoughts of a multi-crew lander: I really wouldn't. Eve is a big step up from landing&lifting anywhere else. Adding extra crew accommodation (or any extra kg of mass in general) will make your craft size/mass balloon. 

Agree,  but The only way of discovering the limits of the possible is to venture a little way past them into the impossible.

[Foxster]

1 minute ago, Spricigo said:

Agree,  but The only way of discovering the limits of the possible is to venture a little way past them into the impossible.

Good point but it is a fairly sound idea to establish the apparent limits of what is possible first. That way you know when you are tiptoeing past that limit into the impossible. 

[Cpt Kerbalkrunch]

Finally, real life is over for the day and I can get back to KSP.

@Razorforce7 All the info I can get is appreciated. My experience with pretty much everything in the aerodynamics section is nonexistent. Just nosecones, fins, and winglets and whatnot. In other words, rocket-type parts. And my op was probably a bit misleading. I was at work and thinking about airbrakes and wondering how they worked, to know if I could use them on Eve, and just posted a quick question. The goal all along was Eve, though. Probably should've put it as one of the tags at least. Sorry about that. I was just a lowly Bottle Rocketeer at the time. I have since been promoted to full Rocketeer, so I am thus more knowledgeable. 

 

@Foxster For whatever reason, the moment I saw one of the airbrake panels swing out for a course correction, I immediately thought it might be helpful on an Eve descent. I like your idea of putting more of them and keeping them out of the "line of fire", so to speak. I only want to put a shield on the nose this time, because of the difficulty of getting rid of the inflatable shield in the gravy Eve calls an atmosphere. I've actually landed a two-Kerbal craft there once before. My go-to method when landing on any planet\moon for the first time is to bring drills along. That way, I only need to get there and I'm assured of getting home. A bit different on Eve, obviously, but I had heard enough about it that I thought I could do it. Took a few tries, but I made it. Couldn't shake the inflatable shield with losing part of my ship with it. Ended up landing on it. Through some glitch I was actually able to drill through the shield and refuel. Left the drills and shield on the surface and took off. Was able to make orbit, but just barely. Had no docking ports or RCS, so I had to EVA my Kerbals to a rescue ship. It feels like I cheated and it still irks me. Technically, I've never "returned a ship from the surface of Eve".

Not this time. Not only am I going to land a two-Kerbal craft, I'm going to make orbit without drilling, and bring them home to Kerbin without refueling.

I'll update with my triumphant (or disastrous) results and screenshots as soon as I have them.