They Say Burn Early On Your Maneuvers, But How Early?

[irichey25]

So, I was just watching one of Scott Manley's videos and during him talking he was talking about how you should burn earlier than your Maneuver Node for maximum efficiency...But how early? I've always really been confused about that, could someone kindly explain to me how exactly it works?

[stupid_chris]

Usually, if my burn time says one minute, I start burning 30 sec before to do half before half after. Just be careful that your burn time makes sense, it bases it off your last acceleration rate and if you've been going more slowly than your max acceleration it won't be the right time.

[rodion_herrera]

There is an estimated time for the burn. What I do is take that time, divide it by two, and I add that time to the remaining time, which gives me the "early" time for the burn. If the burn only takes less than a few seconds, then I dont bother, but if the burn is like 5 minutes long, I do that calculation.

[Tokay Gris]

This is simple to explain:

The maneuver nodes are basically correct, if you could change your velocity instantenously.

Since you can't, some of your burn will be before the node and some after the node. So the idea is to have the actual node in the middle of your burn time.

Say your burn time is one minute. Ideally, your manouver node should be in the middle of that burn time. (like the others said)

That means, you should start your burn 30 seconds before the node, so that you burn 30 seconds before the node and 30 seconds after the node.

One small problem is here, that the nodes seem to be off sometimes by quite a bit. The calculated burn times, I mean.

But if you know your vessel a bit, you can guesstimate by the delta-V required. Say, it says you need 1500 m/s but burntime is given as "4 seconds" you either have a LOT of engines on that craft or the time is way off.

Same thing the other way around (although not as often): If the given delta-V is 5 m/s and the burntime is 5 minutes, you either have an ion-drive, a heavy vessel with a single small engine or the burntime is way off.