Aerobraking at Eve...

[Foxster]

I think that this is the third time I have explained this here: Just mount your air brakes so that they are behind the heatshield before AND after they are deployed...

Rotate them a bit if the clipping of that bothers you...

Will never burn up and they work just fine. 

Edited January 14, 2016 by Foxster

[Fearless Son]

9 minutes ago, Foxster said:

I think that this is the third time I have explained this here: Just mount your air brakes so that they are behind the heatshield before AND after they are deployed...

Will never burn up and they work just fine. 

That is not an aesthetic sacrifice I am willing to make.  

[Foxster]

3 minutes ago, Fearless Son said:

That is not an aesthetic sacrifice I am willing to make.  

Not even rotated as in the 2nd picture so they don't clip? 

Eve is a tough place - you can't afford pretty. 

[Warzouz]

2 hours ago, Foxster said:

Nope. I find air brakes to be an essential part of any Eve lander now, along with a heat shield that has the whole craft shielded behind it. If your craft is heatploding on re-entry then you need both those things. 

Airbrakes explodes at 1200K, this temp is very quickly reached (few seconds) while really decelerating. They can only be open at reasonable low speed (1500m/s ? - I didn't do any tests in 1.0.5). Anyway, the temperature risk is far gone when you're at 1500m/s. Airbrakes are then useless because Eve atmoshpere is very dense. As I've said, I landed a ship without anything in 1.0.4 (well, I slowdown in high atmo with a terrier burning 1000m/s. Terminal velocity was 50m/s). Even drogue aren't necessary.

I'm running some tests on Kerbin reentry vehicles. I'm removing all airbrakes because they are basically useless (I'm testing interplanetary reentry vehicles). They blow in few seconds if you open them, and the even blow if you don't open them (the chutes survives even they aren't protected either...). If I increase the size of the ship (creating a very bulky and ugly ship) the airbrakes also explodes is open.

Basically, airbrakes aren't necessary anymore. I could try to do some tests again on Eve, but I'm quite sure they will blow very soon. In 1.0.4, airbrakes were very useful because very resistant (maybe too much though). I did very extensive tests in 1.0.4. That was my successful 1.0.4 lander + ascent vehicle from 100km Eve orbit (this vehicle was largely overfueled) You may notice there was no heatshield, even heat rises to 95% of critical temp.

For now, I'm waiting for 1.1 to resume playing KSP.

26 minutes ago, Foxster said:

I think that this is the third time I have explained this here: Just mount your air brakes so that they are behind the heatshield before AND after they are deployed...

Rotate them a bit if the clipping of that bothers you...

Will never burn up and they work just fine. 

Well, that's not far from editing the part files and set air brakes heat resistance to a higher value.

[Foxster]

8 minutes ago, Warzouz said:

Airbrakes explodes at 1200K, this temp is very quickly reached (few seconds) while really decelerating. They can only be open at reasonable low speed (1500m/s ? - I didn't do any tests in 1.0.5). Anyway, the temperature risk is far gone when you're at 1500m/s. Airbrakes are then useless because Eve atmoshpere is very dense. As I've said, I landed a ship without anything in 1.0.4 (well, I slowdown in high atmo with a terrier burning 1000m/s. Terminal velocity was 50m/s). Even drogue aren't necessary.

I'm running some tests on Kerbin reentry vehicles. I'm removing all airbrakes because they are basically useless (I'm testing interplanetary reentry vehicles). They blow in few seconds if you open them, and the even blow if you don't open them (the chutes survives even they aren't protected either...). If I increase the size of the ship (creating a very bulky and ugly ship) the airbrakes also explodes is open.

Basically, airbrakes aren't necessary anymore. I could try to do some tests again on Eve, but I'm quite sure they will blow very soon. In 1.0.4, airbrakes were very useful because very resistant (maybe too much though). I did very extensive tests in 1.0.4. That was my successful 1.0.4 lander + ascent vehicle from 100km Eve orbit (this vehicle was largely overfueled) You may notice there was no heatshield, even heat rises to 95% of critical temp.

For now, I'm waiting for 1.1 to resume playing KSP.

Did you see my last post? You don't have to have air brakes burn up. 

I really wouldn't hope that 1.1 is going to change this stuff. Eve is the tough place and so it should be. 

8 minutes ago, Warzouz said:

Well, that's not far from editing the part files and set air brakes heat resistance to a higher value.

How can that be true? They are just rotated. They don't even have to clip if you don't want them to. 

I really feel some of you guys just like failing and/or having something to moan about. 

Edited January 14, 2016 by Foxster

[fourfa]

Foxster - surely you see that in your example, the airbrakes don't actually stick into the free stream - in real life, they would do nothing at all in that configuration.  In KSP, they work great because reasons etc.  Your playstyle uses all the tricks available regardless of realism (rotated intakes, clipping, I'd guess rapierspikes etc).  

Many people don't like to do that.  Their version of success has to look more like reality than yours.  That is a very long way from "you guys like failing" and you know it

I like to know about all these tricks, and use them if there is absolutely no other way in pure stock.  But I prefer not to if I can.  Aesthetics matter to me.

Edited January 14, 2016 by fourfa

[Foxster]

I'll disagree with you there. What it models is that the air brakes are located in the somewhat slowed, curled air that you would find IRL at the rear of a craft with a blunt back end. If you say that that is not modelled in KSP then you can't really argue that using air brakes like this is somehow cheaty either as all bets are then off for realism.  

KSP currently models drag in a totally unrealistic way, with air blowing straight through parts unless they are directly bolted together and the same size. With that level of "reality" I have zero concerns about a bit of air brake rotation, it being closer to reality (as said above) than a lot of other things to do with KSP drag and bow wave heating. 

Edited January 14, 2016 by Foxster

[Foxster]

41 minutes ago, fourfa said:

I like to know about all these tricks, and use them if there is absolutely no other way in pure stock.  But I prefer not to if I can.  Aesthetics matter to me.

I actually feel precisely the same. The craft I use in my game do not use clipping, exploits etc. It's only in areas of ambiguity like this that I make an exception and also when discussing interesting stuff like rotating nosecones to point out it is possible. 

[bewing]

I find that tail fins are superior to airbrakes in all ways. More heat resistant, they give you aerodynamic control after they fulfill their airbrake uses, and provide just the right amount of drag at the back end to keep your craft oriented properly. Just make an action group that toggles the "deploy" function. ATM, there is a bug in KSP that will always make your RV spin when the fins are deployed, but they slow your craft very very nicely while deployed. At eve aerocapture speeds they probably need the heatshield too -- but if you try them I think you will find they always work better than airbrakes.

 

[Foxster]

8 minutes ago, bewing said:

I find that tail fins are superior to airbrakes in all ways. More heat resistant, they give you aerodynamic control after they fulfill their airbrake uses, and provide just the right amount of drag at the back end to keep your craft oriented properly. Just make an action group that toggles the "deploy" function. ATM, there is a bug in KSP that will always make your RV spin when the fins are deployed, but they slow your craft very very nicely while deployed. At eve aerocapture speeds they probably need the heatshield too -- but if you try them I think you will find they always work better than airbrakes.

 

That's pretty interesting. I'll give it a try. 

I can see some limitations though: You can't turn the drag off like you can essentially with air brakes. They also weigh over twice as much. And there is the spinning issue. You can turn on pitch and yaw with air brakes too to use them as some kind of control. You can't tuck them neatly out of the way when unneeded. I like the extra thermal resistance though. 

[Mister Dilsby]

15 minutes ago, bewing said:

I find that tail fins are superior to airbrakes in all ways. More heat resistant, they give you aerodynamic control after they fulfill their airbrake uses, and provide just the right amount of drag at the back end to keep your craft oriented properly.

Yes, quite so! I usually put a horizontal stabilizer on my planes, mounted to a tail above the centerline, and I reverse-deploy the elevons on the tail relative to those on the wing, to get all the drag without changing COL too much. 

 

[Fearless Son]

2 hours ago, Warzouz said:

I'm running some tests on Kerbin reentry vehicles. I'm removing all airbrakes because they are basically useless (I'm testing interplanetary reentry vehicles). They blow in few seconds if you open them, and the even blow if you don't open them (the chutes survives even they aren't protected either...). If I increase the size of the ship (creating a very bulky and ugly ship) the airbrakes also explodes is open.

I think that problem comes when you are trying to airbrake too aggressively.  If you are trying to go from an interplanetary vector straight into a low orbit with a single pass, then of course airbrakes are going to be not worth their weight.  But I find them of some use when making less aggressive aerobreak maneuvers, like one that goes from interplanetary to a highly elliptical unstable orbit, then bring it down to a circular low orbit after several successive passes and a low thrust at the apopasis to stabilize.  In a situation like that, I find that airbreaks save me a lot of time, expanding the craft's surface area to maximize the velocity I shed with each aeropass but without drastically increasing the craft's volume.

Though it would be nice to (eventually) unlock a higher tech version of the aerobreaks which had heat-sink elements on one side of them, allowing them pull double-duty as drag inducers and heat-radiators, with the ability to toggle on and off.  

2 hours ago, Foxster said:

Not even rotated as in the 2nd picture so they don't clip? 

Eve is a tough place - you can't afford pretty. 

More because they look like they are occluded by the shape of the craft itself.  I tend to think that airbrakes should spread wide into the air, like sails.  You could put a sail parallel to the deck of a ship, but you would not expect it to catch much wind.  I realize that the game mechanics allow that, but making something that looks plausible and works as opposed to something that just works is one of those self-imposed challenges.  

[Warzouz]

10 hours ago, Fearless Son said:

I think that problem comes when you are trying to airbrake too aggressively.  If you are trying to go from an interplanetary vector straight into a low orbit with a single pass, then of course airbrakes are going to be not worth their weight.  But I find them of some use when making less aggressive aerobreak maneuvers, like one that goes from interplanetary to a highly elliptical unstable orbit, then bring it down to a circular low orbit after several successive passes and a low thrust at the apopasis to stabilize.  In a situation like that, I find that airbreaks save me a lot of time, expanding the craft's surface area to maximize the velocity I shed with each aeropass but without drastically increasing the craft's volume.

Though it would be nice to (eventually) unlock a higher tech version of the aerobreaks which had heat-sink elements on one side of them, allowing them pull double-duty as drag inducers and heat-radiators, with the ability to toggle on and off.  

Your idea of a dedicated high speed airbrake would be very nice. The issue is that some parts do better jobs than dedicated ones. For example shock cones air intakes has less drag than a regular cone. That basically non sense if the shock cone is not connected to any engine.

Yes, I'm testing reentry vehicle. For now I use a lot of space stations around various bodies. Then I manage crew rotations. for now I was leaving 2 crew (one scientist and one engineer). My reentry vehicle is basically 2 stacked landing pods. With a small heat shield, the pod goes up to 5000m/s at pe. I managed to get to 6500m/s with a medium heat shield, but the ship look ugly and I can't LKO 2 of them at the same time.

When the airbrakes are usable, your speed has already been lowered a lot and quickly reducing to a "chute-safe" speed (even without drogues). My standard 2 seat pod is able to open chute at 7000 to 8000m. I could even land in the mountains... No need of airbrakes or drogue. I'm nearly sure that if you survive Eve heating, chute speed opening is not a problem, so airbrakes ar useless.

I started looking for reusable vehicles which would circularize at LKO the dock to a space station. Crew would be carried by refueling freighter (probably a SSTO space plane). But this kind of return vehicle is more bulky and costs more fuel. the target space station will have to refuel it and I don't want to have to do 2 mining trips to refuel one return vehicle.

[Fearless Son]

Something I really want to see are tweakables on airbrakes that let the user set their maximum deployment.  That would be another point in their favor, when you just want a little drag but not a whole lot.  Compared to chutes, which can be tweaked for altitude they fully deploy at, they cannot really be deployed selectively (you cannot make a chute half open, or just a quarter open, for example.)

[g00bd0g]

I just finished my first krewed Eve mission. This ship can survive a direct insertion to aerobrake as long as the PE is above 75k or so. It takes about 8 more passes to get a nice low circular orbit. Also, of note, you don't even need "ablator" in the heatshields for this profile, they just get hot but don't explode.

I did have to use a bunch of LFO vernier RCS thrusters to keep the thing perfectly prograde or any offending bits getting out of line behind the heat shield would burn.

Only needs a couple hundred DV to capture and circularize to LEO.

 

 

 

 

 

Edited January 15, 2016 by g00bd0g