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Can't get reentry right in 1.05


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I have no idea what you guys are talking about. I've re-entried dozens of times with Chute+Command Pod+Science Jr+Service bay+Heat shield. As a matter of fact, that has been the standard re-entry configuration since getting the game in December.

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6 hours ago, sormi said:

I have no idea what you guys are talking about. I've re-entried dozens of times with Chute+Command Pod+Science Jr+Service bay+Heat shield. As a matter of fact, that has been the standard re-entry configuration since getting the game in December.

Except that he's got two Science Jr., not a Science Jr. and a service bay.  The service bay is shorter than the Science Jr. is, and (if you have at least 0.1 tons of stuff in it, which I assume you do, otherwise why would you be using it?) heavier.

Also the issue with the upside-down heat shield, which apparently makes a difference (which I wouldn't have expected... learn something new every day!)

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Add an empty FL T-100 fuel tank to the top of your creation.  

This lowers the center of mass relative to the total length of the re entry vehicle.

This arraignment re entered without SAS on.

http://imgur.com/a/zI4HQ


Note: This is not to replace all the good advice in the previous posts.  My early career re entry vehicles are typically follow their suggestions:
Parachute, two Sci. Jr., Service bay with batteries, goo and misc., on top of a Mk1 pod then heat shield.

It's always good to have multiple solutions.

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On 1/25/2016 at 5:01 PM, Snark said:

The heat shield may very well be upside-down... but that's not the problem.  The problem is that there are two very big, very low-mass Science Jr.'s slung under the command pod.  The CoM is way towards the nose end, so it's going to want to go nose first.  Having the heatshield flipped one way or the other isn't going to make an appreciable difference to drag behavior.

Don't even need a scientist.  Any EVA kerbal can pull science out of a science experiment and stash it in a command pod.

The benefit you get from a scientist is that they can reset a used goo unit or Science Jr.  For example, if that ship had a scientist on board, it would only need one Science Jr. instead of two (since it would be re-usable).

 

Thanks -- just recovered 10,000 science from a mission to Ike all on a single command pod that reentered.  Only needed 1 of every science experiment on the lander (although i brought 2 because symmetry).

Had I think 75 science experiments in the command pod, carried none of the science instruments back with me.  Hit 6 biomes on Ike in 3 landings + 3 hops.  Reentry vehicle was pretty much just a Mk2 with a heatshield and a parachute (think I had a couple lights and antenna as well).  Got 5 kerbals up to lvl 4 in the process.  Everything collected was from within the Duna/Ike SOI, I already had all the Kerbin/Kerbol SOI science collected.

Edited by Jim DiGriz
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41 minutes ago, Jim DiGriz said:

Thanks -- just recovered 10,000 science from a mission to Ike all on a single command pod that reentered. 

Woot!  Congratulations.  :)

41 minutes ago, Jim DiGriz said:

Only needed 1 of every science experiment on the lander (although i brought 2 because symmetry).

Just to make sure you're aware-- you don't actually need the symmetry.  Except for the goo unit, all the radially-attached science experiments are physicsless, meaning that they add their mass and drag to their parent part rather than having it on their own, which means you don't need to bother with symmetry at all.  Including the 2nd copy doesn't achieve anything other than adding a little bit of mass/drag and a whole lot of cost to the ship.

The goo unit's not physicsless, so that's the only one you need two of in order to balance (unless you can perch one perfectly on top and centered).

For example, the core of my typical science-lander design is:

  • a Mk1 lander can
  • a Science Jr. perched on top
  • a pair of goo units slung front-and-back just under the octagonal part of the can (i.e. so the front one's under the kerbal's feet when he pops out of the hatch)
  • one each of thermometer, barometer, seismograph, gravioli detector; these are placed just beside the hatch (two on either side) within easy arm's reach for a kerbal on the hatch
  • if it's an atmospheric world, a pair of flow variometers stuck on the sides of the Science Jr.  (It's physicsless, so technically i only need one.  However, I like to have two, for a couple of reasons.  For one thing, it's so huge that it looks really ugly and stupid if I just have one.  For another, I frequently want to be able to grab two copies of it before I have an opportunity to go out and grab the science, e.g. one "while flying over __" and another "in upper atmosphere over ___".)
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11 minutes ago, Evanitis said:

A user recently gave me an idea to save on the heathshield / parachute budget

Yep, that's a fun design.  Another variation on that:  drop the stubby wings on the front (so all you have is the AV-R8 winglets on the back), and keep a little parachute on the nosecone.  Then you have something that can come down just fine on either land or sea.  The winglets make it plenty steerable, and you get plenty of body lift off the fuselage even without the wings.  (Dropping the wings up front makes it a bit easier to launch, since having the airfoil surfaces up top of a multi-stage rocket tends to make it want to flip, and can be a bit awkward.)

I use this type of design all the time for my tourist missions.

Edited by Snark
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2 hours ago, Snark said:

Woot!  Congratulations.  :)

Just to make sure you're aware-- you don't actually need the symmetry. 

Game mechanics?  Agreed.  OCD?  Disagree.

I didn't know that fact quite in the detail, but I was aware that I could easily stack up to 4x of the four little experiments on one side of a rocket and it didn't make any difference in flight, so I'd always known it was at least negligible...

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2 minutes ago, Jim DiGriz said:

Game mechanics?  Agreed.  OCD?  Disagree.

I didn't know that fact quite in the detail, but I was aware that I could easily stack up to 4x of the four little experiments on one side of a rocket and it didn't make any difference in flight, so I'd always known it was at least negligible...

Oh, I certainly hear ya on the OCD, brother.  :)  And if it's for aesthetic reasons, fine.  Just wanted to make sure you knew that you don't have to for physics reasons.

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I never knew this about the physicsless parts!  I started playing around, using RCS Build Aid to show which ones have physics and which ones don't.  Funny about the antennas - the Communotron 16 (tiny inline retracting antenna) and 88-88 (big round dish antenna) are physicsless, but the DTS-M1 (folding square antenna) has physics.

Also I only recently figured out that when your maneuver node starts wandering around at the end of a burn, it's because of minor mass asymmetries.  Trying to compensate for non-existant symmetries from little science parts is where it came from.  RCS Build Aid for the win.

Edited by fourfa
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1 hour ago, fourfa said:

RCS Build Aid for the win.

By the way:  Not to take anything away from RCS Build Aid's coolness, but are you aware of what happens to RCS thrusters when you turn on fine control mode?

Details here, but the TL;DR is that they get magically smarter, and the distribution of your RCS thrusters around your CoM becomes much less important because the stock game automatically adjusts them to compensate for off-center CoM.

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I guess I did know that, though my personal OCDness is rewarded when all translation forces balance to zero with only 4 RCS thrusters.  So I just like to do that first

Besides the wandering node is under engine thrust anyway.  RCS might let you chase the node faster, but better to balance everything so the node doesn't wander.  That can only be done in the VAB.

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11 hours ago, Snark said:
11 hours ago, Jim DiGriz said:

Game mechanics?  Agreed.  OCD?  Disagree.

...

Oh, I certainly hear ya on the OCD, brother.  :)  And if it's for aesthetic reasons, fine.  Just wanted to make sure you knew that you don't have to for physics reasons.

My interpretation is that the physicsless components are just a visual representation of something that you would just put inside the ship - probably the cockpit. In reality you would have a tiny port which is closed most of the time for a small thermometer sensor to pop out of. The rest of the thermometer (the bit that stores the measurement etc.) would be inside - i.e. real life clipped into the body. Something like the Gravoli sensor would not need for anything to reach outside.

This allows my OCDness to put them on the outside of the craft.

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