Parachute Cut at <0.5m/s?

[Diazo]

Okay. I'm wondering about a design decision made on parachutes that caused me to kill Jeb last night.

I had popped my chute to slow me down, but I was still coming in hot as I approached 500m and I was worried my chute would rip off at my high speed when opened fully, so I activated my engine to slow me down.

I made it in time and slowed down enough that the chute did not rip off, in fact when the chute opened fully and yanked my pod up it was a stiff enough jolt that my pod hit a net velocity of less then 0.5m/s and so the chutes cut automatically.

At 500 meters.

I was out of gas to do a skycrane type landing and could only watch as Jeb cratered into the ground.

Trying to figure out what happened, a search of the forum led me to the fact that chutes cut automatically if either a) the ship lands, or the ship's net velocity is less then 0.5m/s.

As I had the chute deployed for several kilometers, my horizontal speed was essentially zero and I then zeroed my vertical speed with the engine and chute deployment jolt at 500m.

I am now trying to figure out why the <0.5m/s condition exists. If you are doing some sort of aerobraking maneuver you don't want to get that slow anyway and the chutes can be cut manually for mid-flight maneuvers like that.

I can't think of any other reason a condition to automatically cut parachutes exists in mid-air.

So, before I take this to the suggestions forum to remove that condition on parachutes, I wanted to see if the community had a valid reason for this condition existing before I take it to the devs.

D.

[KatzOhki]

That explains a couple crashes I had last night... No I don't like this either.

[Lazro]

Tbh, I don't really see a reason. Just seems like a "seemed like a good idea at the time" sort of thing. I guess it's good for skycranes as you land? Maybe? Although if that were a thing then it should disappear at 0 m/s...

[J.Random]

So, before I take this to the suggestions forum to remove that condition on parachutes, I wanted to see if the community had a valid reason for this condition existing before I take it to the devs.

Erm.. because in such situation parachute would deflate and become a twisted mess, I guess? I would remove the "landed" condition - to make parachutes usable as aircraft drogue chutes, but auto-cut at low net speed seems quite reasonable.

[Blue]

I've always thought that the parachutes cut if your travel vector inverts. In other words, you're falling down and the parachutes slow you. Fire up your engine and begin to have an upward velocity, and they cut themselves rather rather than fllipping around to slow the new ascent.

[toomuchbrew]

I had a few issues of this last night. One other thing I have noticed though is that some times my chute self-deploys. This caused a crash too as it cut away at full-deployment altitude. I was still falling about 50m/s and it cut away and I made a crater.

[Diazo]

Erm.. because in such situation parachute would deflate and become a twisted mess, I guess? I would remove the "landed" condition - to make parachutes usable as aircraft drogue chutes, but auto-cut at low net speed seems quite reasonable.

But that means parachutes can auto-cut at any altitude if your net speed happens to be (almost) zero for an instant.

And then you get craters when it's your rocket doing this.

Since aircraft drogue chutes is a viable concern, what about changing it from an either condition to an and condition?

So the ship (rocket or plane) must be landed, and speed must be below 0.5m/s for the chutes to auto-cut, instead of only requiring one of those conditions to be true.

For my rockets, the only condition I care about is the landed condition. If you want to add other conditions to make drogue chutes for planes work I'm all for it, but they need to include the landed condition to get around the issue I am having.

D.

Edited October 18, 2013 by Diazo

[sal_vager]

If you have some altitude and your Kerbal is brave enough, you could EVA and repack it

[BostLabs]

Chute can tangle/get hung up and not be able to deploy.

Chute catches fire from rocket.

Chute gets ripped to shreds from high speed exhaust.

the result of all of that is a crater. . Unless you learn throttle control.

[Diazo]

Chute can tangle/get hung up and not be able to deploy.

Chute catches fire from rocket.

Chute gets ripped to shreds from high speed exhaust.

the result of all of that is a crater. . Unless you learn throttle control.

And I'm okay with all those happening as those make sense. (And what do they have to do with a net zero velocity?)

Botching a perfect decent because your pod had a net velocity of zero for an instant makes no sense.

Note that your pod only has to have a net zero velocity for a single update frame for this auto-cut to happen, there's no time delay involved. That's why going from upwards velocity to downwards velocity auto-cuts parachutes. For a single physics update where the pod is switching direction, it has the net zero velocity needed.

D.

[BostLabs]

And I'm okay with all those happening as those make sense. (And what do they have to do with a net zero velocity?)

Botching a perfect decent because your pod had a net velocity of zero for an instant makes no sense.

Note that your pod only has to have a net zero velocity for a single update frame for this auto-cut to happen, there's no time delay involved. That's why going from upwards velocity to downwards velocity auto-cuts parachutes. For a single physics update where the pod is switching direction, it has the net zero velocity needed.

D.

At zero or a positive increase will cause the chute to deflate and fold. It is cut to avoid all those nasties that I mentioned. (Well it is cut because the game can't collapse the chute and ropes on top of your ship or have it flutter around. The game engine does not support it from what I understand.) What I'm suggesting is that if you had watched your vertical speed indicator more closely you could have seen that was going to happen and either cut your throttle or decrease it to avoid your chute going away.

i almost had that happen to me last night. (Never talk to your wife and fly at the same time). I did catch it in time to avoid the chute from being cut.

also, the games does not do rope physics.

Edited October 18, 2013 by BostLabs

[Diazo]

And I'm supposed to react in that instant when the chute pops and then immediately cuts?

It was something like two update frames, significantly less then a second, between the chute opening and the chute cutting as I'd noticed my too fast speed late and so had the engine at max, with the intention of cutting the engine as soon as the chute popped.

If I crash a rocket because I screw up, that's on me and I have no issue with it.

When I crash a rocket because a game mechanic makes no sense I have issues. The chutes vanishing because I get unlucky and hit zero net velocity for an instant is a game mechanic that makes no sense.

D.

[Dkmdlb]

And I'm supposed to react in that instant when the chute pops and then immediately cuts?

No you're supposed to plan ahead so that you don't have to do an unplanned emergency deceleration burn right when the chutes are about to open.

[BostLabs]

No you're supposed to plan ahead so that you don't have to do an unplanned emergency deceleration burn right when the chutes are about to open.

that is what I do.

or you could have a second chute.

[BubbaWilkins]

No you're supposed to plan ahead so that you don't have to do an unplanned emergency deceleration burn right when the chutes are about to open.

If your chute cannot safely deploy without destroying your craft, then your craft is either too heavy or needs more chutes. Everything else is an attempt to make a poor design work. It can be done, but the flaw is in the original craft.

[Wheffle]

I think it's a silly condition. I'm not totally sure why it's in there.

To all the realism people who are saying the chute will deflate, I'm not sure the chutes are all that realistic to begin with, seeing as how 15 chutes packed into a tight area will not tangle or get messed up even as the ship's vector changes and they wiggle around. Kerbal chutes are different, obviously!

Also, I've changed vertical direction before on a landing and I've seen the chutes flip sides without cutting (flying like a noob trying to land a rover on Duna). Cutting at low speeds seems to be inconsistent. Maybe a slight horizontal velocity kept the chutes from cutting or something. Also, yet another testament to the odd kerbal chutes, as none of the strings got caught on anything wrapping around the craft 0_0 quantum strings!

[Starwhip]

I've had this happen many times. Just let the 'chutes do their thing and only open them if you are falling. (In other words, don't open them to keep yourself from going up.)

[J.Random]

If your chute cannot safely deploy without destroying your craft, then your craft is either too heavy or needs more chutes. Everything else is an attempt to make a poor design work. It can be done, but the flaw is in the original craft.

Actually, his craft needs (1) struts and/or (2) drogue parachutes. Adding normal parachutes will make the craft even more likely to be torn apart by gee-force at 500m.

[BubbaWilkins]

Actually, his craft needs (1) struts and/or (2) drogue parachutes. Adding normal parachutes will make the craft even more likely to be torn apart by gee-force at 500m.

I believe that first chute unlocked (which I assume is the one he is using) does act as a drogue, hence the two states of deployment. But it won't work if the mass of the craft is too high which was my original point.

[Diazo]

Okay, I just looked back at the thread and realized I left one rather important fact out.

When the chutes deployed I was still going in the realm of 70-80m/s with the engine on full burn. The design I had going had 100m/s as the safe chute speed limit at 500m. (I did say I was coming in hot.)

I consider it broken that I can be going 70 m/s one instant and then the chutes deploy and I've hit net zero velocity fast enough that I am not able to react in time to hit X to cut thrust.

Alternatively, I look at it this way.

A required element for safe landing should not have any condition that stops it working that is not initiated by me. Chutes auto-cutting away are not under my control and I want to change that.

If I crash, it should be because I make a mistake, not because of some random game element.

The only 'mistake' I made was starting my retro burn to slow down to parachute release speed a few second after the ideal moment. Otherwise the flight was perfect.

That is not something that should cause me to lose a rocket.

D.

Edited October 18, 2013 by Diazo

[BostLabs]

<snip>

If I crash, it should be because I make a mistake, not because of some random game element.

The only 'mistake' I made was starting my retro burn to slow down to parachute release speed a few second after the ideal moment. Otherwise the flight was perfect.

That is not something that should cause me to lose a rocket.

D.

You are not going to like this answer. My apologies in advance.

You did make a mistake. The chute cutting off like that, for that set of circumstances, has always happened. It's not random.

as the game cannot do rope or cloth physics the only thing left, other than detach (go away), is for it to stick up in the air like a ballon. That would look very silly.

i guess it could do part of its billowing animation. But what Does it do when you are going up? Go back to drogue mode?

here is another option. You have coding skills (I really want to try your mod). Make a better parachute.

Edited October 18, 2013 by BostLabs

[Diazo]

Well, in a game where realism has lost out to game play for keep things fun, I am of the opinion that this is another place where that should happen.

I can flip rockets end over end and recover, I can botch burn times and staging release (yes, I meant to bring those empty SRBs with me to orbit) and so on.

Then parachutes sneak up and don't have the forgiveness the rest of the game does. I argue that they should have that same forgiveness, hence this thread.

And yes, I have thought about adding something to my velocity control mod to cover this situation. Nothing that has come to mind so far would work though.

D.

[BostLabs]

I'm suggesting you make a new part mod. Not an addition to your existing mod.

My modeling skills are nonexistent, but I can code in C#. I'd be willing to assist, and I'm fairly sure that if a thread was started in the addons section you could find a few more helpers.

pretty sure that an animation of a chute collapsing could be done. Then when the velocity forces are applied again, snap the chute open again in the direction it needs to go. If the collapsing animation completes, then the chute cuts. That should give anyone enough warning on what is going to happen.

Edited October 18, 2013 by BostLabs

[lammatt]

chutes cut itself when your vertical velocity changes sign.

- you have your chute opened in a descend, and you throw in an upward thrust which stops the descend and make your craft ascending instead, you chute will cut itself