Operational flexibility in launches in bad weather vs delta-v margin.

[speedevil]

In principle, it seems reasonable that you can trade off significantly between launch reliability and margin.

Naively, slowing down 100m/s from what would be max-q at 4km-10km in altitude, and sacrificing ~300m/s^2 or so to gravity losses.

Wouldn't it make sense to plan a lower than optimal energy trajectory, if it allows an increasing likelyhood of not violating the decreased range limits, due to lower stresses during max-q and lower velocity through clouds?

Clearly, some payloads don't have the margin.

Or is in practice the amount it helps not worth it.

[Jim]

In principle, it seems reasonable that you can trade off significantly between launch reliability and margin.

Naively, slowing down 100m/s from what would be max-q at 4km-10km in altitude, and sacrificing ~300m/s^2 or so to gravity losses.

Wouldn't it make sense to plan a lower than optimal energy trajectory, if it allows an increasing likelyhood of not violating the decreased range limits, due to lower stresses during max-q and lower velocity through clouds?

Clearly, some payloads don't have the margin.

Or is in practice the amount it helps not worth it.

It has to with controllability from winds aloft and not max q

[deruch]

Big difference between flying through air and water/ice.  Also wind shear is about lateral forces on the vehicle not maxQ.  But the big question is why would you sacrifice anything when you can just wait a day or two for the weather to change?  How many payloads really need to launch right-now?  Answer: zero.

[RonM]

Big difference between flying through air and water/ice.  Also wind shear is about lateral forces on the vehicle not maxQ.  But the big question is why would you sacrifice anything when you can just wait a day or two for the weather to change?  How many payloads really need to launch right-now?  Answer: zero.

Obviously true for the typical launch, but that got me thinking about ICBMs. They have to launch when the order is given no matter the weather. Any steely-eyed missilemen out there know how an ICBM would react launching in bad weather?

[speedevil]

Big difference between flying through air and water/ice.  Also wind shear is about lateral forces on the vehicle not maxQ.  But the big question is why would you sacrifice anything when you can just wait a day or two for the weather to change?  How many payloads really need to launch right-now?  Answer: zero.

Windshear is not maxQ, but the forces involved would surely lower if you're going slower?

What  sacrifice?
If you're able to launch more of the time, and recover with adequate margins.

[deruch]

Big difference between flying through air and water/ice.  Also wind shear is about lateral forces on the vehicle not maxQ.  But the big question is why would you sacrifice anything when you can just wait a day or two for the weather to change?  How many payloads really need to launch right-now?  Answer: zero.

Obviously true for the typical launch, but that got me thinking about ICBMs. They have to launch when the order is given no matter the weather. Any steely-eyed missilemen out there know how an ICBM would react launching in bad weather?

ICBMs are built to different standards with different tolerances.

[jg]

And are geographically dispersed and important targets redundantly targeted...

[douglas100]

....What  sacrifice?
If you're able to launch more of the time, and recover with adequate margins.

The supreme sacrifice would be loss of mission. What customer would risk that by pushing against the weather limits? Launch vehicles already have different software loads to handle different wind conditions after launch.

My guess is that flying the initial part of the ascent more slowly gains you little in the way of safety in wind shear conditions and looses you a lot in gravity losses. I doubt the weather limits are set too conservatively. There's a lot to loose if you get it wrong. It's simple, if the weather is red you don't fly.

[Wayne Hale]

Biggest weather problem - at least for the Florida Space Coast - is lightening.  No rocket is really built to sustain a lightning strike;  not just the electronics are at risk but the possibility of an attachment that melts a hole in the side of a tank is very real.  When you look closely at the reasons for weather related launch scrubs, even if you took out all the wind, ceiling, wind shear, etc., causes, the potential for lightening strike would dominate the statistics. 

[Coastal Ron]

Big difference between flying through air and water/ice.  Also wind shear is about lateral forces on the vehicle not maxQ.  But the big question is why would you sacrifice anything when you can just wait a day or two for the weather to change?  How many payloads really need to launch right-now?  Answer: zero.

Obviously true for the typical launch, but that got me thinking about ICBMs. They have to launch when the order is given no matter the weather. Any steely-eyed missilemen out there know how an ICBM would react launching in bad weather?

ICBMs are built to different standards with different tolerances.

Plus there are typically more of them being launched during an attack, so if one or two fail because of weather the overall goal won't be significantly affected.

The calculation for commercial or exploration launches would likely not anticipate needing to launch during severe weather conditions.