Parachute Failure, PLEASE HELP

[justmeman117]

Hi. I've been with KSP for a couple years now, and I don't think I've been more stumped since.

First of all, I'd like to say I fully expected the recent aerodynamic/thermodynamic changes to the game. I was a little split on the issue, but now that it's here... Well, it's gotten really difficult to play, but I like that the game is leaning towards realism.

My issue is that the parachutes seem a little... Too far. I'm currently trying to launch a rocket into sub-orbit. In order to keep the rocket from reentering parachute first, I had to re balance the craft, and did so by dumping the unnecessary heat shield and replacing it with an engine and small tank. Now it enters engine first, which is good.

But no matter what I do, it simply doesn't bleed speed fast enough, and no matter what I do to the chutes, they ALWAYS FAIL.

So I enter from an apoapsis of about 100km altitude, at about 45 degrees. I know it's been pretty steep. But even in 1.01 and 1.02, I hadn't had any issues with an entry like that. Now, even with a deployment altitude of 50 meters (bare minimum), and pop them at 500-700 meters, coming in at 250 m/s (note, LESS than the speed of sound), flames going away at about 3,000 meters, no heat bars showing up for chutes, chutes protected in small bays, it always gives me that same stupid message, "Aerodynamic/Thermodynamic Failure", and fails the second I press space bar.

Is this really realistic? I don't think a real parachute would fail only semi deploying at a speed of 250 m/s at ANY altitude, would it?

I'm wondering if it IS realistic, but the fact that Kerbin's atmosphere is a lot thinner between the surface and the edge than Earth's is getting in the way of an accurate portrayal of a reentering object. I'm only just coming out of reentry flame by the time I'm just 1000-3000 meters. It's like there just isn't enough room to slow down before deploying chutes.

Is there any way to get around this? What do the thresholds look like for safe parachute deployment in 1.04?

Edited July 1, 2015 by justmeman117

[S1mancoder]

Try to check parachute info window (open it by right mouse click on it) before deploying - it says if it's unsafe, safe or risky. Open only at safe. If you will still loose your chutes even if it's saying "safe" - then probably you encountered some kind of bug. Thresholds by the way are below 240 m/s as well as I know.

It's like there just isn't enough room to slow down before deploying chutes.

And the problem is that you're have only like 1.25 m diameter surface to slow you down with small size, yea? It is more than enough to slow down a drone with weight of 0.1 ton. Its pretty enough to slow down capsule of 0.8 ton. But its not enough to slow down a capsule+empty_tanks+engine for total of 2-3 tons, and that is your case. Also you should consider aerodynamics of a surface you're going first into atmosphere, because the better it is, the worst brake you will have.

How you can deal with it:

- Separate engine stage and capsuse on falling down. You will have twice more surface to brake down now (one on separated engine stage, one on capsule) and it will be almost 100% enough for capsule still engines will crush the ground on higlands and mountains eventually. If you want to have your cash back from engine stage use Stage Recovery mod.

- Add winglets (tail fins are perfect for that) of any king and deploy them by right clicking and pressing "deploy" on reentry. They will increase surface that will be stopping you, efficiently acting as an aerobrakes, also they will cause instability that will eventually turn your craft around, also increasing surface exposed to coming air. Also winglet brake efficiency depends on control surface area, so use one's with the biggest.

- Just leave some fuel to slow yourself down burning retrograde during descent.

Edited June 29, 2015 by S1mancoder

[Chaos_Klaus]

Actually, 260m/s is the threshold at which parachute deployment becomes safe. Do you stage them earlier? Drogue chutes can handle more I believe.

A capsule+heatshield will slow down enough. When your object is heavier, you need to come in more shallow. Put your periapse between 30km and 40km depending on where you come from. Suborbital, well ... how high is your apoapse?

But even in 1.01 and 1.02, I hadn't had any issues with an entry like that.

Yeah, because in 1.0.2 there was no reentry heat to be afraid of. 1.0.3 reduced the drag again and increast the heating effects, so that reentry would be more challenging.

I don't think a real parachute would fail only semi deploying at a speed of 250 m/s at ANY altitude, would it?

That would obviously depend on the chute.

[-ELF-]

I haven't had a chance to test changes in 1.0.4, as I am having the issues with parachutes (they crash the game the second I pick them in the VAB), but anyway, entyering at 45 degrees seems to me that you must hit the ground without even going out of reentry effects... I am entering the atmosphere at about 5 degrees all the time, to bleed of speed before even going lower to atmosphere.

Latest reentry from minmus was done with PE set to 35 km, took 5 passes to actually go suborbital and land, but landing was very smooth, 150 m/s at about 2 km over the surface. Like a charm.

P.S. I am not doing precise landings anytime, it is too tedious.

[Signo]

Sorry if this is a silly question, but did you open the bay before deploying the chutes? Deploying in a closed bay may result in an aerodynamic failure.

[Goddess Bhavani]

So I enter from an apoapsis of about 100km altitude, at about 45 degrees. I know it's been pretty steep. But even in 1.01 and 1.02, I hadn't had any issues with an entry like that.

The reason why there are no problems with earlier versions -

Steep re-entry will always be cushioned by the 'souposphere', which is some sort of transparent cream of mushroom that stops any and all objects from impacting the ground at any more than 100m/s in freefall. Not really an accurate description but you get the idea.

Now, in 1.0.4, if your object/vehicle/rocket is aerodynamic enough it will simply, well, rocket through the atmosphere and not slow down in time to deploy parachutes. 45 degrees is a very, very steep angle and requires a blunt body ballistic re-entry at high Gs, meaning, something like a Mk. 1 command pod and heatshield. That shape creates enough drag that it will slow down in time pulling upwards of 7Gs and slowing down enough to deploy your parachute safely at about 5,000m. The re-entry flames dissipate way before that.

I suggest to re-enter at a shallower angle and with a 'blunter' craft, Mk.1 pod creates enough drag on its flat side to slow down automatically. A long stick with an engine at the back may re-enter back end first, but a long thin rod is considered an aerodynamic, roughly bullet shaped object and will not slow down in time for you to deploy chutes.

Also, don't enter the atmosphere at 45 degrees. Start your re-entry maneuvering by decreasing your periapsis to the planet's surface, i.e. 0m. This ensures a gentle re-entry allowing you to get used to handling thermal stresses of re-entry.

If you do insist on re-entering long, thin objects, stick a few wings on it and see if you can make a micro-shuttle like that. Then, instead of re-entering nose first (and losing little speed while heating up to catastrophic levels), fly it like the Space Shuttle at 30-45 degree angle of attack. This way, you are exploiting blunt-body physics to increase drag and decrease thermal heating at the same time, just like how real re-entry vehicles work!

Edited June 29, 2015 by pandoras kitten

[Grumman]

Also, don't enter the atmosphere at 45 degrees. Start your re-entry maneuvering by decreasing your periapsis to the planet's surface, i.e. 0m. This ensures a gentle re-entry allowing you to get used to handling thermal stresses of re-entry.

What you're saying is that a sub-orbital flight isn't going fast enough to land safely. That's absurd. If you're not going fast enough to reach orbit in the first place, that should make it easier to burn that velocity off, not harder.

[Goddess Bhavani]

What you're saying is that a sub-orbital flight isn't going fast enough to land safely. That's absurd. If you're not going fast enough to reach orbit in the first place, that should make it easier to burn that velocity off, not harder.

I've had V-2 range sub-orbital missions end up not bleeding enough speed off and lithobraking; it depends on the craft characteristics and shape, which is the point of my entire posting. Certain shapes will literally just spear right through the atmo without slowing much, like aforementioned ballistic missile.

[Chaos_Klaus]

What you're saying is that a sub-orbital flight isn't going fast enough to land safely. That's absurd. If you're not going fast enough to reach orbit in the first place, that should make it easier to burn that velocity off, not harder.

Please think about that again and notice why it is wrong.

It's about vertical an horizontal velocity. If you go horizontally through the atmosphere you take a longer path through the atmo and therefor have more time to slow down.

If you're not going fast enough to reach orbit in the first place, that should make it easier to burn that velocity off, not harder.

Go tell that to physics. But don't wait for a reply.

Don't just say something is absurd before thinking it throug. That is not very scientific.

[selfish_meme]

What you're saying is that a sub-orbital flight isn't going fast enough to land safely. That's absurd. If you're not going fast enough to reach orbit in the first place, that should make it easier to burn that velocity off, not harder.

If you go straight up, you come straight down, that's suborbital and lethal, in real life too.

[Warzouz]

Drogue chutes can be open at 500, maybe 600 or 700 (to be tested). They are efficient to slow down for regular chute opening. You don't need many drogue chutes. For my 250 tons recoverable stage, I use 24 chutes and only 2 drogue chutes. Even the 24 chutes are far from sufficient to land this monster.

If you have the tech, use "airbrakes".

Don't hesitate to use your engine to slowdown before opening you chutes. If you only miss 200m/s a quick burn can make the difference between life and death. Again, it's about balance. If you keep your engines, you'll come a bit faster. But drag is more important than mass.

I've managed auto-open chutes parameters. Of course that depends on your ship drag.

- Set your drogue chute for 0.35 and 5000m

- Set your chutes for 0.65 and 800m

- Deorbit from LKO for 60m/s on the crater 90° west of KSC

- Stage all your chutes, they'll deploy automatically

- You should land quite near KSC (again, depending on your drag)

But beware of the mountains, chutes won't open fast enough to land on them. You'll crash.

[Grumman]

If you go straight up, you come straight down, that's suborbital and lethal, in real life too.

No, it's not. That's standard operating procedure for sounding rockets like the Black Brant.

[Lelitu]

And lethal for man rated rockets.

A shallower angle of entry is much more survivable in 1.0.4 aerodynamics.

Shallower re-entry gives a lower vertical velocity component, which means it takes longer to reach the ground.

Longer time to reach the ground means more time losing speed to drag, this makes it possible to lose enough speed to pop your 'chute safely *before* hitting the ground.

You do wind up getting more heat, and do have to dissipate more energy, but it *is* more survivable

because you have more time to dissipate the energy, and time goes up faster than energy.

[Grumman]

And lethal for man rated rockets.

It's been done three times with man rated rockets - twice with the Mercury-Redstone rockets and once with a Soyuz.

[BasKing]

In-game, if you go in with a vertical drop from say 80k, your speed will be way over 350m/s at ground level: not slow enough to deploy the chutes...

Pre-1.0.4 you could get away with vertical drops: it would slow you to around 250m/s at 1500m, enough to deploy chutes safely, but that is just not the case anymore:

you will have to return at an angle, enough to make the air-break happen long enough to drop to 250-m/s and deploy chutes, before you hit the ground.

Or fire an engine to get speeds below 250m/s, then deploy chutes. I think you can do that as high as 4000m or even a little bit higher perhaps.

Not too high: there must be enough air. Don't know the exact boundary. I use the angled approach, and mostly don't have the ÃŽâ€v to spare anyway.

[KSK]

It's been done three times with man rated rockets - twice with the Mercury-Redstone rockets and once with a Soyuz.

Freedom 7:

Shepard's mission was a 15-minute suborbital flight which reached an altitude of 101.2 nautical miles (187.5 kilometers) and traveled a downrange distance of 263.1 nautical miles. (487.3 kilometers)

Liberty Bell 7:

The flight lasted 15 minutes 30 seconds, reached an altitude of more than 102.8 nautical miles (190.4 km) and traveled 262.5 nautical miles (486.2 km) downrange, landing in the Atlantic ocean.

No idea about the Soyuz but neither of the Mercury-Redstone flights were straight up and down.

[Reactordrone]

The reason why there are no problems with earlier versions -

Steep re-entry will always be cushioned by the 'souposphere', which is some sort of transparent cream of mushroom that stops any and all objects from impacting the ground at any more than 100m/s in freefall. Not really an accurate description but you get the idea.

Souposphere is something of a misnomer since the actual atmosphere hasn't changed since the release of 1.0.0 and the pre 1.0.0 atmosphere was actually thinner than the current version. It's only the way drag is modelled that has changed since the 1.0.0 release..

[tutike2000]

As of 1.0.3/1.0.4 drogue chutes, heat shields, air brakes are actually useful/needed.

A craft composed of pod+tank+engine only will not have enough drag to slow itself down enough in order to use regular chutes. (At least not in a steep reentry)

Either add more drag, burn retrograde, add heat shields, add air brakes, or anything else you can think of to slow yourself down.

[Jouni]

Safely reentering with a rocket is obviously much harder than with a pod. Unless you absolutely have to recover the engines and fuel tanks, drop them (and all other unnecessary parts) before reentry.

If you want to fly through the atmosphere without drag slowing you down, make your craft tall and thin. If you want the drag to slow you down, make your craft short and wide. These apply both during the ascent and during the reentry.

[LostOblivion]

Freedom 7:

Shepard's mission was a 15-minute suborbital flight which reached an altitude of 101.2 nautical miles (187.5 kilometers) and traveled a downrange distance of 263.1 nautical miles. (487.3 kilometers)

Liberty Bell 7:

The flight lasted 15 minutes 30 seconds, reached an altitude of more than 102.8 nautical miles (190.4 km) and traveled 262.5 nautical miles (486.2 km) downrange, landing in the Atlantic ocean.

No idea about the Soyuz but neither of the Mercury-Redstone flights were straight up and down.

Indeed. And at this shallow angle (compared to straight down) Shepard experienced up to 10 gees.

[A_name]

AIRBRAKES are your friend.

[mrclucks]

Not sure why you're trying to reenter at such a steep angle. 30-35km is the sweet spot for me. Steep enough that I won't spend too much time in the flames(even from interplanetary), but shallow enough that if I don't lose enough momentum i wont lithobrake.

Only annoying thing is when I lose just enough speed that I miss periapsis and rise up to about 70km and go back down.

A periapsis of 50-40km is too shallow for me since it will take many orbits to finally fall down to kerbin.

[Sharpy]

Yep, A.I.R.B.R.A.K.E.S. is the solution. It bleeds the speed off the orbit really well, and stabilizes the descent. Just make sure to rightclick and switch "yaw" and "pitch" controls off on them. They are not very good as control surfaces. But braking...

Here's atmospheric reentry in a little open speeder.

That's from the orbit. The solar panels are still whole.

[Goddess Bhavani]

That's wonderfully effective!

But airbrakes don't appear yet for those in ultra-low-tech career progress. Maybe I'll try sticking girders to the outside

[Lelitu]

That's wonderfully effective!

But airbrakes don't appear yet for those in ultra-low-tech career progress. Maybe I'll try sticking girders to the outside

Reentry angle is far more important than airbrakes.

The truly critical peice of technology from career for easy re-entry is actually the decoupler.

A pod+heatshield+'chute can trivially survive re-entry at up to 35 degrees and 3kps (maybe higher, I havn't personally tested higher)

The troubles come with a steeper re-entry, or carrying more mass.

As heating is now in 1.0.4, parts recovery value is a trap. you'll spend at least as much as you save, and far more stress than is fun trying to recover extra bits of rocket.