Help with parachutes (Newb)

[Giygus]

I am still pretty new to Career mode, and I am trying to build a rocket to ferry 4 tourists into a sub-orbital flight, and land it in the water.  The issue I am having is that the section made to splash down comes in with great speed, and it cannot be saved with parachutes.

This is what I got over all:

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And this is what I want to hit water, note that fuel tanks are empty in this pic, to show you a true center of mass:

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And here it is seconds before disaster, note that Jebediah is enjoying himself, while the passengers realize they should have donated the funds to charity (Orphans from Launch Failures being the largest on Kerbal right now) :

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OK, so a few things I noted while trying to fix it myself.

1) The craft DOES flip, and yes I understand that is a bad thing

2) The parachutes are at default settings. 

3) My reentry orbit is kind of shallow, I point at 70 degrees after the SRB stage.  However, when I went down to 65 or 60 degrees, I have the same issue, only my fuel can run out before I hit 70Km +.

The reason why the word "Parachute" is in the title is because I read on the wiki that parachutes "should always be toggled for your craft (or something like that)" but I could find no rules regarding how to set them up.  The only tutorial here was :

but it only talks about parachute placement, not how to set them up specifically.

As I advance along career mode, I will need to splash larger and heavier things, so I figure now would be the best time to ask around, see what tips I can get.  One of the things that confuses me the most about this is the fact that a smaller 2x tourist set up seems to work just fine, slowing down very quickly when it gets into the thicker part of the atmosphere.  And the only real difference between the 2 is one small fuel tank and one passenger section. 

Thanks for your time!

[ForScience6686]

One problem you have is a poor drag ratio.  You have a long stack and a small area to induce drag.  When you are in the upper atmosphere use the side of the craft to create more drag.  And ensure you are coming in tail first once in the thicker atmosphere.  Also keep your pe around 20-35km to give you plenty of time to slow down.

[linuxgurugamer]

First off, jettison the engine and tanks.

Second you need to reenter retrograde, the way you are, you aren't slowing down

If you have airbrages, add and use them

You need to be below 250m/sec to deploy the chutes.  You could also separate each module and land each.  This will be a bit trickier, you will need to flip between the three until the chutes are deployed

Fourth, do 2 or 3 different missions to do the 6 kerbals; they don't all need to be done at the same time

[N_Danger]

You can right click on the chute in the vab or in flight to adjust the opening altitude You want set it to a higher altitude than the default. But you do have watch your speed as others mentioned.

[Snark]

Your problem is that your re-entering spacecraft is lawn-darting.  It's too aerodynamic in that nose-first configuration, and it's so stable (with the pointy nose and the fins on the back) that you probably can't make it enter any way other than nose-first, amirite?

If you could fly that ship sideways, then atmospheric drag would be plenty to slow it down well below 250 m/s long before it hits the ground.

Even if you can't go fully sideways, if you could just steer it some to keep the nose about, say, 30 degrees above prograde, then body lift will keep your descent shallow and you'll go nice and slow.

Have you unlocked any steerable fins, such as the AV-R8 winglet?  If so, put a pair of those on the left and right side of the reentry ship, in place of the Basic Fins.  That will give you enough steering ability on the pitch axis that you can nose-up and slow down a lot.

2 hours ago, linuxgurugamer said:

First off, jettison the engine and tanks

That might not help much in this case-- his problem is that he's lawn-darting, and eliminating that heavy engine on the back will just make his reentering ship even more nose-heavy and could make it even harder to get out of "prograde lock".  I suspect that steerable fins would help a lot more.

2 hours ago, linuxgurugamer said:

Second you need to reenter retrograde, the way you are, you aren't slowing down

That might also not help a lot.  The ship is really aerodynamically stable nose-first, not tail-first, so I suspect that even if he enters retrograde, there's a high likelihood that aero forces will wrench the ship around prograde as soon as the atmosphere starts to get thick.

[Plusck]

2 hours ago, Giygus said:

As I advance along career mode, I will need to splash larger and heavier things, so I figure now would be the best time to ask around, see what tips I can get.  One of the things that confuses me the most about this is the fact that a smaller 2x tourist set up seems to work just fine, slowing down very quickly when it gets into the thicker part of the atmosphere.  And the only real difference between the 2 is one small fuel tank and one passenger section. 

If anything, it'll get easier later. Bigger rockets have bigger areas to create drag. You'll be unlikely to be bringing in very long, big rockets, and you'll have things like drogue chutes to help you if you do.

So yes, your problem is that you have a very pointy object with a heavy tip and few options to control it. Your parachute placement looks fine, should be a soft enough landing/splashdown if you can get slow enough to open them.

That just leaves the problem with slowing down.

Since it's a suborbital flight, you really must try to get the angle of ascent (and therefore descent) as shallow as possible. No two ways about it. Also coming in tail first should help, as others have said.

Next up, control options. Do you have any controllable fins? That might let you get a decent angle of attack on the way back down, which will help slowing. You might want to move them up the rocket a bit if you do (yes, this is bad for the flipping-on-ascent issue, but should make it easier getting your nose off prograde on the way back). What about torque wheels? Or if all else fails, RCS?

Finally, design options. It will be draggier on the way up, but you could always attach your tourists' cabins radially near the engines. You'd need to add the smallest fuel tanks (emptied) first since they won't radially attach on their own. Not exactly first class service, but then you would certainly be able to slow down on the way back. That would also require more fuel to get suborbital too.

Edited March 20, 2016 by Plusck

[Plusck]

I was thinking something along these lines:

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Still under 20t and only 21 parts. I don't think you need five parachutes - three should be enough - but I'll test it just in case. It has massive TWR so it's a fight just to get it heading at enough of an angle on the way up.

[Giygus]

18 minutes ago, Plusck said:

I was thinking something along these lines...

Excellent, and it does look cool to!  I did not even think about putting them on the side like that ( I keep not thinking around corners in this game, I need to work on my design skills ).  I bet you could scale it up to 3 and have it function as well.

45 minutes ago, Snark said:

...Have you unlocked any steerable fins, such as the AV-R8 winglet?  If so, put a pair of those on the left and right side of the reentry ship, in place of the Basic Fins.  That will give you enough steering ability on the pitch axis that you can nose-up and slow down a lot...

I have all lvl 45 cost tech unlocked, so I have basic ones yes.  I did try at one point to put four Delta-Deluxe winglets on, but it didn't really help.  Maybe the asymmetrical design will.  I am off to try anyway!

[Snark]

1 minute ago, Giygus said:

Excellent, and it does look cool to!  I did not even think about putting them on the side like that ( I keep not thinking around corners in this game, I need to work on my design skills ).  I bet you could scale it up to 3 and have it function as well.

I have all lvl 45 cost tech unlocked, so I have basic ones yes.  I did try at one point to put four Delta-Deluxe winglets on, but it didn't really help.  Maybe the asymmetrical design will.  I am off to try anyway!

Four Delta-Deluxe Winglets should totally work.  I was suggesting doing just the left-right in order to save cost. 

If you have a specific example of it not-working with the steerable winglets on the back, post a screenshot?

[Giygus]

A couple of other points. 

I did try pointing retrograde, and as Snark figured, I flipped around anyway.

I tried it with ditching engine block (not that I want it like that, the point is to make money) and that didn't help either.

 

[Plusck]

Just now, Giygus said:

Excellent, and it does look cool to!  I did not even think about putting them on the side like that ( I keep not thinking around corners in this game, I need to work on my design skills ).  I bet you could scale it up to 3 and have it function as well.

I just tried it out - worked fine as long as it re-entered facing retrograde. In the lower atmosphere it'll be impossible to hold at retrograde, but after assuming a slight angle it stays stable and slows down to under 250 m/s at about 4000m.

I also tried coming in at a flatter angle (retrograde, with nose pointed down) and in the higher atmosphere it immediately adopted a prograde position, was impossible to turn around and ran into the ground at over 700 m/s. So yes, engines first on reentry !

[Giygus]

OK, so, I added 2 AV-R8 Winglets, and it worked!  It is a little wobbly on the way up, and when I had the 2 fins all the way down near the bottom, I kept flipping on the ascent.  I pointed Retrograde, and had Jeb set to hold it, so as it came down, he kept jamming that control stick around until it was slow enough.  I suspect I will need more barf bags for the tourists.

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Snark:  Here are pictures of the not working one.  I put the Delta-Deluxe winglets back on like yesterday, and tried twice.  Once with me pointing retrograde coming down, with Jeb set to steady, and once with Jeb set to point retro all the way down (Jeb leveled up for me today, so I could not do this earlier).  It is very steady on the way up, and as you said before, becomes a steady lawn dart on the way down.

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Edited March 20, 2016 by Giygus
Pictures into Spoilers

[wumpus]

21 hours ago, Snark said:

Your problem is that your re-entering spacecraft is lawn-darting.  It's too aerodynamic in that nose-first configuration, and it's so stable (with the pointy nose and the fins on the back) that you probably can't make it enter any way other than nose-first, amirite?

If you could fly that ship sideways, then atmospheric drag would be plenty to slow it down well below That might also not help a lot.  The ship is really aerodynamically stable nose-first, not tail-first, so I suspect that even if he enters retrograde, there's a high likelihood that aero forces will wrench the ship around prograde as soon as the atmosphere starts to get thick.

One way to help fix this that doesn't require any cost or further unlocking of the tech tree (although I really love those AV-R8 winglets.  Don't try high TWR launches without them.) is to simply stick the fuel tanks above the passengers (no FAA/OSHA/Health and Safety issues on Kerbin).  Since the engine is heavier  than the capsule, moving the passengers down should easily move the center of mass (with empty/nearly empty) fuel tanks should mean easily coming down prograde.  Maintaining a small bit of reserve fuel (nowhere near the 10% space-x uses) should get you under the ~220m/s needed to release the parachutes.

As far as landing horizontal, one way that works would be to only use parachutes along a single side.  Two parachutes should be enough.  Unfortunately, you probably can't afford an asymmetric rocket that small.  Use symmetry to place to guide chutes (or just use what's already there) to place individual parachutes (no symmetry) just under where the old ones were, then remove the parachutes placed with symmetry.  Then put your "real" parachutes on a stage above your "dummy" parachutes.  Land with just your "real" parachutes (I have no idea if you can open your dummy chutes in time if two aren't enough.  Note that groups of three should work better in that you should still float horizontal, and you only need one "dummy" parachute out of three.  Sufficiently big rockets shouldn't have to bother with dummy chutes.

[Hodari]

One other option is to simply split it up into 2 smaller missions.  Just because all of the tourists are part of the same contract, doesn't means they HAVE to all go together(and for more complicated itineraries, you don't have to visit all of the destinations for any one tourist in the same mission either).  Of course, it may be more cost effective if you can combine them as much as possible, but if you're having trouble designing a ship to handle all of them at once, it's an option.,

Fins on the bottom of your final stage are definitely what you DON'T want to have.  If anything, you can put them upside-down on the TOP of that stage to help keep it pointing retrograde, though you'd want to have a fairing around it and/or larger fins on the bottom of lower stages during launch.  This probably shouldn't be needed though.

Even on suborbital flights,try to re-enter at a very shallow angle.  Especially with something like this, your ascent should probably be almost the same as an actual orbital flight, just skipping the circularization burn at the end.

On re-entry, if you're having trouble slowing down enough to open the parachutes, one other thing you can do is:  once you have slowed down enough not worry about overheating, turn the ship completely sideways in order to maximize the drag.

[Loren Pechtel]

One other thing I have learned about craft like that that like to lawn dart:

If you get stuck prograde, wiggle.  Watch your craft, always command a turn in whatever direction it's currently turning.  While I've never broken a prograde lock this way I can get it oscillating pretty strongly and you get a lot more drag during those oscillations.  Amazingly, the tourists don't seem to mind the flight that redefines "Vomit Comet".

You do have a reaction wheel on there, don't you?

[AeroGav]

On 20/03/2016 at 4:27 PM, linuxgurugamer said:

First off, jettison the engine and tanks.

This is valid if it leaves just  a capsule and heat shield behind,  but even without engine and tanks his vehicle is going to lawn dart.   The problem with dropping the upper stage is that he'll have to move his steerable fins up the rocket if he's to have use of them in his hour of need, and that's going to mess with CG.

Rearranging things to put fuel at the top, kerbals in the middle and upper stage engine at the bottom has a couple of  advantages

1. re-entry heat is borne by the fuel tanks..  they will pop first to save the crew.

2. empty tanks are lighter than the kerbally bits, cg moves aft a bit and makes the design less lawn darty than it would otherwise be.  Of course, you could decouple the terrier motor as well to take things further in that direction.

Punching off the engine would be mad, because it is the only object behind the fins to offset the nose down moment posed by the weight of the crew cabins.

 

Edited March 23, 2016 by AeroGav
caught myself talking nonsense

[Giygus]

On 3/23/2016 at 7:48 AM, AeroGav said:

 

That is such a funky looking plane!  A James Bond villain would love it!