Staging: Delay or "Fire in the Hole"?

[Motokid600]

Too bad ullage motors have no place in stock KSP yet, as they would add another very interesting dimension to our staging events.

Not sure if there are any mods which mimic it...

Engine Ignitor

NEEDS to be stock. Players should have to atleast deal with ullage. ( limited ignitions isn't necessary in stock ) It adds an awesome layer to launches. Really hope it gets updated one day. I prefer the term hot staging. I do that a lot in RSS with blowout panels made out of 8x procedural fairings. I eject four of them when I stage and it makes for a really cool effect.

As for stock... No I delay. I usually over power my first stage so by time I seperate I'm high and fast enough to perform some fancy staging.

Also... Ladies and gentlemen be very careful. Hot staging in the lower atmosphere can shove your upper stage and flip it over.

Edited June 24, 2015 by Motokid600

[AdmiralSirJohn]

The radial boosters *will* hit your center stage. But did you notice what's the unit of impact durability of components? m/s. If you go with your engines off, they will bounce off harmlessly. If you're going 20m/s relative to them when they bounce, things *will* explode.

The "untouchable" approach is difficult to execute. Accept that things will collide, bounce, scratch, just make sure they do it within allowable force, and things get much easier.

If you get better at that, you can accept controlled destruction of parts as an important aspect of the game.

I have a return/reentry vehicle with an mk3 passenger cabin, a cargo bay, a fuel tank just big enough to get back home, and a weak engine of good ISp. And *not enough parachutes* to slow it down to a safe landing speed.

The engine is the crumple zone. It explodes upon ground impact, producing just enough upward force to slow down the rest to a safe speed.

Damn the 1.0.3 new thermal model. Yesterday I was testing an abort sequence for my SSTO MK3, and couldn't get it right. The idea was to include a bunch of separatrons inside the cargo bay (just behind the cockpit) and make them fire into the walls. By destroying the cargo bay, the cockpit would get separated. OTOH yesterday I successfully made a cluster bomb. Lots and lots of separatrons on a liquid fuel fuselage, plus a strut with a couple separatrons aimed *into* the fuselage. As it explodes it frees the 100 or so separatrons attached to it, flying *roughly* in direction the thing was aimed.

Simply, an engine/solid fuel booster can change any part into a decoupler.

I find that judicious use of separatrons will negate this.

And that sucks about your abort test, but I bet it was funny as anything...

[Kryxal]

Funny, I'm not having any trouble with collisions anymore ... though with the BIG SRBs, radially mounted, I use a single separatron mounted just far enough on to the aerodynamic cap on top that it starts to angle in. Works every time...

[Megadeath]

Like most, it seems, I mostly use FitH staging, for reasons of awesomeness and keeping the staging list short but do use the 2 step for precision.

Someone mentioned earlier FitH faces challenges IRL that KSP doesn't model. I can imagine some kinda blow back issue from firing the engine with a surface to reflect it, is that it, or part of it? Also, if anyone cares to explain ullage I'd be greatful. I know I can look this up, but I love community support for this game, and figure other uninformed/unintelligent/unmotivated people would benefit from an explanation here too.

Cheers in advance!

[Superfluous J]

My radially mounted things almost never collide with my center stack. Usually when they do a single sepratron on each will do the trick.

I tend to FitH stage unless I'm doing something special.

[Juicy]

The radial boosters *will* hit your center stage. But did you notice what's the unit of impact durability of components? m/s. If you go with your engines off, they will bounce off harmlessly. If you're going 20m/s relative to them when they bounce, things *will* explode.

The "untouchable" approach is difficult to execute. Accept that things will collide, bounce, scratch, just make sure they do it within allowable force, and things get much easier.

If you get better at that, you can accept controlled destruction of parts as an important aspect of the game.

I have a return/reentry vehicle with an mk3 passenger cabin, a cargo bay, a fuel tank just big enough to get back home, and a weak engine of good ISp. And *not enough parachutes* to slow it down to a safe landing speed.

The engine is the crumple zone. It explodes upon ground impact, producing just enough upward force to slow down the rest to a safe speed.

Damn the 1.0.3 new thermal model. Yesterday I was testing an abort sequence for my SSTO MK3, and couldn't get it right. The idea was to include a bunch of separatrons inside the cargo bay (just behind the cockpit) and make them fire into the walls. By destroying the cargo bay, the cockpit would get separated. OTOH yesterday I successfully made a cluster bomb. Lots and lots of separatrons on a liquid fuel fuselage, plus a strut with a couple separatrons aimed *into* the fuselage. As it explodes it frees the 100 or so separatrons attached to it, flying *roughly* in direction the thing was aimed.

Simply, an engine/solid fuel booster can change any part into a decoupler.

Long radial placed stages indeed tend to collide every time, and can't be escaped. Short, single or two-tank boosters can generally be escaped before they angle in far enough to collide with my main rocket. I need to put the radial decoupler on the top tank of my two-tank boosters though, so their rear angles in. If I put the radial decoupler on the bottom tank, the frontside angles in and it WILL indeed hit my ship. 3-tank boosters tend to angle in faster than I can clear them, but I rarely use those for efficiency reasons anyway.

[Cairol]

It depends.

If I know my stage will be used during ascent to orbit, I decouple and activate the engine of the next stage in one go.

If I know my stage will not be used during ascent or that I won't have to stage during a maneuver,

I first decouple and then activate the engine in the next stage manually as soon as I need it.

[zozatos]

Like most, it seems, I mostly use FitH staging, for reasons of awesomeness and keeping the staging list short but do use the 2 step for precision.

Someone mentioned earlier FitH faces challenges IRL that KSP doesn't model. I can imagine some kinda blow back issue from firing the engine with a surface to reflect it, is that it, or part of it? Also, if anyone cares to explain ullage I'd be greatful. I know I can look this up, but I love community support for this game, and figure other uninformed/unintelligent/unmotivated people would benefit from an explanation here too.

Cheers in advance!

Basically, what he was talking about is that KSP does not model ullage. When a rocket motor cuts out, the rocket is now under zero acceleration. This means that all of the liquid fuel in the tanks just floats around. Getting gas into the turbopumps that fuel the rocket is bad for them, so generally there will be small engines called "ullage motors" which push the rocket up, which pushes the fuel inside the tank downwards (towards the main engine plumbing). Then the main engine can start. With "Fire in the hole" either the explosive bolts from the stage separation act as your ullage motors, or the previous motor is still running and provides ullage. Then you start the next stage engine without having to carry ullage motors. Thus efficiency.

[Megadeath]

Thanks!

[Kryxal]

This time, I had a bit of an odd collision mishap ... I had a rocket with SRBs and 4-way asparagus, and the SRBs ran out just before the first asparagus drop. The SRBs dropped fine, then the tank on the "high" side hit and wrecked the rocket. My eventual solution was to turn the rocket 90 degrees during launch, then turn it back for the next pair to drop.

[Ripper2900]

One additional trick I use is to put the radial separators towards the front end of the boosters, with a strut at the bottom. It's hard with the srb's but easily done with liquid ones.

This pushes the top away more than the bottom and gives a cleaner separation. The bottom of the boosters are easily avoided by the FitH tactic, as you accelerate away, it's always the parts higher up that tend to collide. One very large liquid boosters though a radial separator is not enough. Sepatrons are needed.

I try to avoid any sort of interaction with spent boosters - it's simply too risky.

[Cairol]

One additional trick I use is to put the radial separators towards the front end of the boosters, with a strut at the bottom.

I'm doing the same. The Sepratrons on top of each booster are usually set to 0.8 fuel units, to not make the booster moving funnily.

It's just enough fuel to get the top part away from my rocket.

The bottom part is no danger, because of accelerating away after staging.

[AlexinTokyo]

One additional trick I use is to put the radial separators towards the front end of the boosters, with a strut at the bottom. It's hard with the srb's but easily done with liquid ones.

This pushes the top away more than the bottom and gives a cleaner separation. The bottom of the boosters are easily avoided by the FitH tactic, as you accelerate away, it's always the parts higher up that tend to collide. One very large liquid boosters though a radial separator is not enough. Sepatrons are needed.

I try to avoid any sort of interaction with spent boosters - it's simply too risky.

You can use the offset gizmo to do this with the SRBs; very easy with Thumpers, but needs a little zooming around to get it to work with Kickbacks.

[wumpus]

Hopefully this is before the necro cut-off...Real life rocketry: changing the delay between stages may be the difference between making orbit and blowing up:http://qz.com/281619/what-it-took-for-elon-musks-spacex-to-disrupt-boeing-leapfrog-nasa-and-become-a-serious-space-company/ (fairly close to the end)tl;dr - the only difference between the Falcon [1] that made it into orbit and the previous one that blew up was “Between the third and the fourth flight we changed one number, nothing else,†Koenigsmann said. “That was the time we needed to separate the two stages.â€Â

[AdmiralSirJohn]

That's interesting, and with the tweaks to the heat system, it might come into play in 1.1...

[jarmund]

Depends on where on the rocket:

On the booster stage(s), when detatching radially mounted stuff, there are a lot of components that can smash into parts that I want to keep intact. For these cases I prefer to first detatch, and then gently ease my rocket out of the surrounding mess with RCS.

For upper stages, when the only debris is behind me, then I decouple and fire engines at the same time.

[Dispatcher]

When I first started playing KSP, I preferred "fire in the hole" because it consolidated the staging icons used and also just plain looked cool. But over time I shifted to separate staging; primarily as a contingency and for greater control or options. Maybe the poll is akin to asking "6 of one or half a dozen of the other", but that's what I do now. If I ever do switch back, it'll be a mix of "fire in the hole" for launch stages and individually for all else.