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Est Burn Time Query


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When placing a maneuvere node, you get an estimated burn time.  I've noticed the actual burn time is usually a little shorter than the estimate, especially during longer burns.  I wonder, is this because the estimate didn't take account of the reduction in mass due to burnt propellant during the burn?

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Saw the topic title, showed up to pontificate on the subject, saw that I've been efficiently and effectively pre-empted.  So, never mind.  :)

(Though, TBH, what always bugged me the most about the stock "estimated burn time" display wasn't the fact that the timing was off,  it was that nagging persistent "N/A" all the time.  That, and not knowing whether I actually have enough fuel for the burn I just set up.  The latter two were what really prompted the mod, more than the burn time itself.)

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11 hours ago, Vaporized Steel said:

Your not really wondering, your answering your question :D

 

I was seeking confirmation of my own speculations :wink:

Thanks for the answers. One additional question, does the burn time mod effect the games performance much?  I play on an aging laptop and have to have all graphics options turned down to their lowest settings in order to get a nice green mission elapsed timer (most of the time).  It's the main reason I've kept away from mods in the past, but this one sounds almost essential.  And yes, I'm being lazy by asking rather than trying it out, but with limited gaming time, there's always soooo much to do in game!

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8 minutes ago, Clipperride said:

does the burn time mod effect the games performance much?

Not as far as I know, but I'm not the expert.

This is a question probably best posed to the mod's author.  @Snark, can you enlighten us?


Happy landings!

Edited by Starhawk
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4 minutes ago, Red Iron Crown said:

I like KER's burn time estimate, it takes changing TWR and staging into account, and also gives a countdown to start based on half the dV expenditure.

Interesting.  I've used KER forever but I've never paid attention to that feature before.

Happy landings!

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1 hour ago, Snark said:

(Though, TBH, what always bugged me the most about the stock "estimated burn time" display wasn't the fact that the timing was off,  it was that nagging persistent "N/A" all the time.  That, and not knowing whether I actually have enough fuel for the burn I just set up.  The latter two were what really prompted the mod, more than the burn time itself.)

Not just that, but if you do a mini-thrust before the node just so it calculates the burn time, it's possible to burn for too short and it miscalculates, giving waaay longer burn times than it should, and you start your maneuver way ahead of time.

I love your mod, man. Like said above, it is really one of the few I strongly believe should be integrated into stock, as-is (the other ones being Module Manager, Strategia and, most importantly, Chatterer).

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50 minutes ago, Clipperride said:

One additional question, does the burn time mod effect the games performance much?

No, it's very lightweight.  It shouldn't affect your performance at all.  I really cared about perf when I was writing it, so I took great pains to try to ensure that it treads as lightly as possible.

Programmer technobabble, with some examples, in spoiler section for anybody who's interested.

Spoiler

For example, there are some operations that are potentially expensive:  e.g. one of the things BetterBurnTime does is to show you the burn time based on what your ship can actually do (as opposed to the stock indicator, which shows "what has it done recently), which means the mod needs to iterate through all the parts of your ship to identify anything that's an engine and see 1. whether it's active or not, and 2. what direction it's pointed.  Such a scan could get pretty expensive, if you've got a really big ship with many hundreds (or even thousands) of parts.  If the mod did that scan on every single update frame, it would tank your performance as your ships get bigger.

So I put effort into making sure that the mod only does expensive computation operations when it really has to, and caches the results.  In some cases, that involves limiting refresh frequency (e.g. instead of "every frame", do the thing "once per second" and cache the result).  In other cases, that involves triggering on an event (e.g. I know you can't have any new engines I don't know about unless your ship changes its number of parts, so I just cache the list of known engines and iterate over that, and only re-scan the ship when the part count changes).

The TL;DR is that no, it's not expensive.  It's very cheap and lightweight.  Not only did I set out to design it that way, but also I've never once had any complaint about it (which is saying something, given that there are literally thousands of people using it-- it's my most popular mod by far, is currently the #16 most-popular downloaded mod on SpaceDock).  If there were a serious issue, I expect I would have heard something about it by now.

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