Devnotes Tuesday: Wednesday Edition III!

[KerbonautInTraining]

My only complaint with the heat shield is it will be quite out of place. Not exactly stock alike...

But hey, who says you can't change what "stock alike" means?

[Jarin]

With how many bugs Claw fixed when he wasn't on the dev team, I'm looking forward to good things now that he can poke at the source code.

[godefroi]

10 hours ago, RoverDude said:

It doesn't use ablator - it's basically lots of layers of thermal blankets over a bunch of inflated rings.  And folding one of these things back up would be like trying to re-use a car's airbag.  I am sure one could build enough stuff to make that happen, but it's probably a bad idea

Thanks   Just bear in mind we already have a 3.75m heat shield in stock

Does this giant inflatable heat shield protect radially-attached parts? I don't believe that any of the existing heat shields do, even if they APPEAR to, right?

 

9 hours ago, kujuman said:

It really really is, in any likelihood. Minor hopes: significant performance improvement in resource flow (right now it's...pretty heavy). Big hopes? Stackable SRM style resource flow mode (which is actually pretty simple). Best hope? Make fuel flow no longer enum so that mod developers can more easily create custom fuel flow options.

SRMs don't work like that. Making them taller doesn't add burn time, as fuel doesn't "flow" in them, and they almost never simply burn from the bottom up. Solid rockets burn from the *inside out*, so a taller motor simply has more thrust (more fuel burning at once), not more burn time.

[Red Iron Crown]

1 minute ago, godefroi said:

SRMs don't work like that. Making them taller doesn't add burn time, as fuel doesn't "flow" in them, and they almost never simply burn from the bottom up. Solid rockets burn from the *inside out*, so a taller motor simply has more thrust (more fuel burning at once), not more burn time.

By carefully shaping the propellant a different thrust profile can be made. It is entirely possible to have a taller motor with the same (or less!) thrust with a longer burn time.

[godefroi]

10 minutes ago, Red Iron Crown said:

By carefully shaping the propellant a different thrust profile can be made. It is entirely possible to have a taller motor with the same (or less!) thrust with a longer burn time.

I believe they call this a "3D profile", but I gather that it's not common. Varying the channel geometry definitely is, but having it vary top to bottom I think is much less so. If you're arguing for selectable thrust profiles in our solid motors, though, keep talking, you're in the right place. I'd even take a non-adjustable thrust profile that makes more sense, i.e. one that didn't result in a takeoff TWR of 2.5 and a burnout TWR of 13.5 (Kickback sea-level).

[Red Iron Crown]

1 minute ago, godefroi said:

I believe they call this a "3D profile", but I gather that it's not common. Varying the channel geometry definitely is, but having it vary top to bottom I think is much less so. If you're arguing for selectable thrust profiles in our solid motors, though, keep talking, you're in the right place. I'd even take a non-adjustable thrust profile that makes more sense, i.e. one that didn't result in a takeoff TWR of 2.5 and a burnout TWR of 13.5 (Kickback sea-level).

You don't need to go 3D. A cross section with more surface area will burn faster and produce more thrust, one with less will burn slower at lower thrust. And it can vary the amount of thrust/burn rate during the burn. See this diagram from @OhioBob's excellent website:

[KerbonautInTraining]

IIRC the shuttle boosters did have a high surface area star pattern near the top to increase liftoff TWR.

That doesn't necessarily mean they burn from top to bottom though, the ignitor shoots a 30+ meter flame down the chamber to ignite the whole thing at once.

[godefroi]

3 minutes ago, Red Iron Crown said:

You don't need to go 3D. A cross section with more surface area will burn faster and produce more thrust, one with less will burn slower at lower thrust. And it can vary the amount of thrust/burn rate during the burn. See this diagram from @OhioBob's excellent website:

Right, but for any given cross-section, adding more segments on top simply increases thrust, not burn time. For non-end-burning solid rocket motors (by far the most common type outside model rockets and fireworks), adding length increases thrust, changing the channel shape changes thrust profile (i.e. thrust over time).

Edited February 18, 2016 by godefroi

[Red Iron Crown]

1 minute ago, godefroi said:

Right, but for any given cross-section, adding more segments on top simply increases thrust, not burn time. For non-end-burning solid rocket motors (by far the most common type outside model rockets and fireworks), adding length increases thrust, changing the channel shape changes thrust profile (i.e. thrust over time).

Sure. But it's easy to abstract that adding segments also involves changing the profile. After all, we already have tweakable thrust for them, which amounts to the same thing, no?

[monstah]

1 hour ago, richfiles said:

I think KSP only responds to left Shift and Left Control for throttle. Does it respond with the Right Shift+Tab? If That doesn't work, then yeah... Definitely needs fixing.

Will try that, thanks!

[godefroi]

1 minute ago, Red Iron Crown said:

Sure. But it's easy to abstract that adding segments also involves changing the profile. After all, we already have tweakable thrust for them, which amounts to the same thing, no?

Sure, but I think more useful in general would be the ability to vary the profile directly, or simply adjust the profile to make more sense. As it is, SRMs are a) not powerful enough to be generally useful, and b) have thrust profiles that make them unsuitable for many uses. Having longer burn time would only make the problem worse, making the burnout TWR even more crazy high, causing control issues. It might be slightly better if our SRMs had the ability to gimbal thrust (which SRMs in real life generally do).

[Curveball Anders]

1 hour ago, Jarin said:

With how many bugs Claw fixed when he wasn't on the dev team, I'm looking forward to good things now that he can poke at the source code.

It was my first reaction too, but then I remembered that I tried to provoke Claw about the bugs he fixed, but he was in daily chats with NathanKell way before joining the actual crew.

It is of course a good thing to see Claw officially on the team, but not even Claw can do miracles, even with full access

 

[KerbonautInTraining]

38 minutes ago, godefroi said:

Having longer burn time would only make the problem worse, making the burnout TWR even more crazy high, causing control issues.

Don't you mean shorter...?

[0111narwhalz]

6 hours ago, ktmemp said:

I read countless devnotes and this is short version bug fix bug fix 64bit bug fix bug fix whell bugfix bug fix and this is it.I want to see other solar system,hundred new stock parts,better single player experience( like xcom short videos about when I dıscover Duna atmospheric pressure or give me a reason to do something not just for science points),parts we can bend and make our ship unique etc.I know this is not easy but I waiting this patch so long and all I hear bug fix bug fix.

I understand where you're coming from, but at its core KSP is still a fairly unstable game. It desperately needs bugfixes, and 64 bit is kind of a thing that modern games should have, considering that I don't think 32 bit hardware is even still in production.

[magnemoe]

18 hours ago, The Real Franklin said:

At first I thought we were going to see deployable airbags, and I got excited. A deployable shield is okay, too, I guess.

I would like to be able to retract the heatshield. 
Would be very nice for Mun / Minmus fuel runs, engines would be protected by shield during aerobrake. No you could not land with this, at least not without leaving the shield in orbit. 

[Just Jim]

All sorts of good news!!! 
Happy smiles all around for the DEV team!!!

[godefroi]

1 hour ago, KerbonautInTraining said:

Don't you mean shorter...?

Sorry, didn't make that much sense. I guess what I really mean is more propellant, or more accurately, a higher propellant mass fraction without associated adjustments in the thrust curve.

[WillThe84th]

That heat shield looks awesome, it's gonna help a lot!

[ShadowZone]

21 hours ago, SQUAD said:

Bob (Roverdude) wrapped up work on the new inflatable heat shield.  Which surprisingly required a few changes to different part modules to make it work the way he wanted.  For example, it is not re-foldable once it’s out. It also has its own fairing, as well as a built in omni-decoupler  but one that is not in the staging menu (to prevent ‘accidents’). One thing to note is that this part serves mostly as an aerobrake with thermal resistance being secondary, so Bob got to do a lot of testing with interplanetary aerobraking for both Jool and Eve. This is something we think you are going to like and of course, here’s a gratuitous screenshot showing the new heat shield stowed (2.5m) vs. deployed (10m)

OMG I already have so many ideas for this!

The hype for 1.1 is real

[willysw]

Any chance 1.1 might fix the disappearing fairing/shroud issue on heat shields? It seems like this one has been out there awhile.

[KerbonautInTraining]

1 hour ago, ShadowZone said:

OMG I already have so many ideas for this!

The hype for 1.1 is real

I can't imagine the kinds of things you're going to manage with the heat shield and predicted performance increases.

Mobile space station?

Reusable Jool 5?

Interstellar Ark??

(RIP your CPU: 201X - 1.1 release)

Edited February 18, 2016 by KerbonautInTraining

[ShadowZone]

1 minute ago, KerbonautInTraining said:

I can't imagine the kinds of things you're going to manage with this

Mobile space station?

Reusable Jool 5?

Interstellar Ark??

(RIP your CPU: 201X - 1.1 release)

You know, I AM actually working on a new Jool 5 attempt. And I am not happy with how the necessary heat shields limit what I can do with it. soooooo....

[kujuman]

 

4 hours ago, godefroi said:

SRMs don't work like that. Making them taller doesn't add burn time, as fuel doesn't "flow" in them, and they almost never simply burn from the bottom up. Solid rockets burn from the *inside out*, so a taller motor simply has more thrust (more fuel burning at once), not more burn time.

*sigh* First off, I'm probably the person who's spent the most time working on getting realistic SRMs in game, so I (1) don't understand why you think that's what I was saying (2) do know that for SRMs to work well w/ stackable segments in game a new fuel flow mode is necessary*. Secondly, adding propellant in an SRM casing means some combination of added thrust or added burn time because one can shape the grain. Without changing the geometry of the burn surface, just adding segments increases surface area -> increases thrust, but one could also shape the grain to maintain surface area with a taller motor -> increasing burn time. "simply" is so literal.

The biggest challenge with AdvSRBs was trying to get KER or MJ to understand the custom fuel flow for custom engines, because mod makers don't have all of the fuel flow modes that reasonably exist, and they can't teach the game new ones in a simple way.

*Which was the point of the post

[NathanKell]

50 minutes ago, willysw said:

Any chance 1.1 might fix the disappearing fairing/shroud issue on heat shields? It seems like this one has been out there awhile.

AFAIK 1.0.5 already did. Can you reproduce it in stock 1.0.5?

[StrandedonEarth]

1 hour ago, willysw said:

Any chance 1.1 might fix the disappearing fairing/shroud issue on heat shields? It seems like this one has been out there awhile.

When you attach a decoupler to a heat shield, you can attach it 2 ways, depending which node it attaches to. The lower attachment leaves a gap covered by a fairing, which I believe still disappears. I'm not sure because since 1.05 I use the upper attachment which leaves no gap, therefore no fairing to disappear.