Decoupler Ejection Force

[Ncog Nito]

Just for verification to make sure I understand it right, the ejection force, mainly concerning radial decouplers, is what determines how far away from a launch vehicle the separated part is ejected.  Right?

[Ty Tan Tu]

Pretty much, it specifies the DeltaV with which the part separates. More massive parts, are of course, going to have less separation. And if the launcher has high mass and the part is small, it is going to change the parts trajectory. I mention that because I once did that. I was pointing prograde when I separated a Mk1 Command Pod for reentry only to find my pericenter was above 70k. I had to send a rescue mission... LOL

 

[bewing]

Yes, it specifies how much push the decoupler uses in both directions to separate the parts.

 

[Ncog Nito]

Thanks...

[Loren Pechtel]

On 4/28/2017 at 4:31 PM, Ncog Nito said:

Just for verification to make sure I understand it right, the ejection force, mainly concerning radial decouplers, is what determines how far away from a launch vehicle the separated part is ejected.  Right?

How far away is distance.

Distance is velocity * time.

Velocity is force / mass.

If you're in space time doesn't really matter, the part just keeps going.  However, if you're trying to separate a booster you only have a second or two before drag takes over.

Mass is also very important.  I'm currently hauling tourists to LKO in an bus made up of multiple 1.25m stacks and I want the rocket to be draggy on the way down (it has no heat shields and becomes uncontrollable at roughly 15,0000m)--thus I send the nose cones flying before coming down.  With the decoupler only separating a nose cone it takes off very fast indeed!

[Kryxal]

Under those circumstances I tend to send nose cones flying when I'm ascending, at maybe 60 km and engines stopped.  I usually then delete it later (since it would deorbit if I went and looked at it).

[Spricigo]

38 minutes ago, Kryxal said:

Under those circumstances I tend to send nose cones flying when I'm ascending, at maybe 60 km and engines stopped.  I usually then delete it later (since it would deorbit if I went and looked at it).

Is that the case where a piece of debris end in a orbit such 50kmx150km? And since its on rails it don't get slowed by drag? It something that annoy me a bit, the 'need' to delete it.

On the other hand, I have some LV that leave debris in a long suborbital trajectory, so flighting to the destruction, and I delete it anyway because I'm opening the tracking station for whatever reason.

[klesh]

On 4/28/2017 at 8:25 PM, Ty Tan Tu said:

 I was pointing prograde when I separated a Mk1 Command Pod for reentry only to find my pericenter was above 70k. I had to send a rescue mission... LOL

 

Which unfortunately is one of the problems when you set decoupler or seperator force to 0; it still imparts a force upon decoupling/separating.  Do it in the wrong direction and your transfer stage won't smack into the moon as planned, it'll sail right by.  I've taken to paying attention to my orientation prior to decoupling a stage now.