Monoropellant as dead weight on rockets etc?

[Cloakedwand72]

Hi Monopropellant as dead weight on rockets etc?Do rockets have dead weight in real life like using monopropellant as dead weight on my ship designs? 

[GDJ]

I've used unused monopropellant as ballast and/ or trim weight for my larger planes. Nothing wrong with what you're doing.

[Snark]

37 minutes ago, Cloakedwand72 said:

Hi Monopropellant as dead weight on rockets etc?Do rockets have dead weight in real life like using monopropellant as dead weight on my ship designs? 

Nothing wrong with using it that way if you want to.

Real-life rockets tend to avoid dead weight at all costs-- space travel is expensive.  Every gram counts when each kilogram costs thousands of dollars to orbit.

[Empiro]

You can do that, but the question is why would you want to?

Other than the rare case of having to balance out an asymmetrical payload (and even then, try to shape your payload so that it is symmetrical), there's no reason to carry dead weight around.

[FancyMouse]

Real life? There's a lot of weight for redundancy/reliability that can be consider dead weight in KSP sense, because KSP doesn't model all possible failures that would be seen IRL. For example you never put two probe cores on your rocket for a single ship, do you?

Edited January 26, 2016 by FancyMouse

[Wemb]

7 hours ago, FancyMouse said:

Real life? There's a lot of weight for redundancy/reliability that can be consider dead weight in KSP sense, because KSP doesn't model all possible failures that would be seen IRL. For example you never put two probe cores on your rocket for a single ship, do you?

Yup - you wouldn't do that in KSP - on the other hand, how many of use have had to use our RCS systems for propulsion when we accidentally ran out of fuel? Let alone using the jetpack to get out an push.That's pretty common in KSP, but I can't recall that even being in done in IRL.

 

Wemb

[MagicFireCaster]

If you don't need it , don't carry it, in the case of the monopropellant on your command pods it isn't even enough to affect your rocket at all, so don't worry a lot for it.

[Kelderek]

I've needed to use ballast on a couple designs, most notably on a 1.25m design with a command pod and a few other items like science Jr. and small service bay, I added a small fuel tank just before the heat shield to ensure the correct end of the vessel points retrograde for re-entry.  Those command pods are notorious for wanting to flip..

[StarManta]

16 hours ago, Snark said:

Nothing wrong with using it that way if you want to.

Real-life rockets tend to avoid dead weight at all costs-- space travel is expensive.  Every gram counts when each kilogram costs thousands of dollars to orbit.

The recent ORBCOMM launch by SpaceX had 11 satellites and 1 mass simulator (e.g. ballast) because they had to have a balanced load. This may not be quite so unusual.

[Workable Goblin]

7 hours ago, Wemb said:

Yup - you wouldn't do that in KSP - on the other hand, how many of use have had to use our RCS systems for propulsion when we accidentally ran out of fuel? Let alone using the jetpack to get out an push.That's pretty common in KSP, but I can't recall that even being in done in IRL.

 

Wemb

Maybe not the jetpack push (due to lack of jetpacks; but see STS-51-A), but the use of RCS systems as propulsion has occurred a number of times to save a mission after some problem with the main propulsion. For instance, TDRS-1 suffered an upper stage failure but was able to reach its planned orbit through use of the attitude control thrusters, and there have been a number of other geostationary satellites that were saved in similar fashions.

[wumpus]

45 minutes ago, StarManta said:

The recent ORBCOMM launch by SpaceX had 11 satellites and 1 mass simulator (e.g. ballast) because they had to have a balanced load. This may not be quite so unusual.

That is bizarre.  Did one fail tests at the last minute, of they just couldn't come up with a way to package 11 birds?  I'm sure that space-x would be happy with a little more fuel for the return.  I really doubt they planned on shipping ballast when they designed the satellites and mission, but I wonder when it changed.

Edited January 26, 2016 by wumpus
added last sentence.

[sal_vager]

I've had to use an RCS tank to balance an Apollo style lander, the other side had a rover and I didn't want to carry two.

[StarManta]

2 hours ago, wumpus said:

That is bizarre.  Did one fail tests at the last minute, of they just couldn't come up with a way to package 11 birds?  I'm sure that space-x would be happy with a little more fuel for the return.  I really doubt they planned on shipping ballast when they designed the satellites and mission, but I wonder when it changed.

The deployment device... thing was a set of 3 things with 4 connectors each. I'm guessing it would've been more trouble to design the third thing with 3 balanced connectors. Personally, I'm kind of surprised they didn't include 1 more satellite just for redundancy, but presumably they ran some numbers somewhere and decided it wasn't worth the cost. Or maybe they'd originally planned for 12, and didn't have time to finish building all 12 when the launch date was coming up. Honestly, you'd have to ask ORBCOMM whether that was part of the plan or not.

[Wemb]

15 hours ago, Workable Goblin said:

Maybe not the jetpack push (due to lack of jetpacks; but see STS-51-A), but the use of RCS systems as propulsion has occurred a number of times to save a mission after some problem with the main propulsion. For instance, TDRS-1 suffered an upper stage failure but was able to reach its planned orbit through use of the attitude control thrusters, and there have been a number of other geostationary satellites that were saved in similar fashions.

Interesting stuff.   I must say that some sort of subsystem equipment failures that (slightly) break various components could add an interesting gameplay dynamic for career mode.

Wemb

[Starhawk]

I've used monoprop tanks to balance spaceplanes before.  I usually rationalize it as emergency reserve propellant.

The nice thing is that you can place the tank and then empty some mono out if needed to fine tune the balance.

Happy landings!

[StrandedonEarth]

The Space excrementstle had ballast in the engine compartment to put the Cg in the right place for landing. Of course, most of the Shuttle was dead weight during launch anyway so it wasn't a big deal. One improvement in Buran was the ability to pump RCS fuel between the fore and aft tanks for Cg control.