What is the most useless thing in KSP?

[foamyesque]

11 minutes ago, Corona688 said:

Unless you're using modded parts, reaction wheels are so ubiquitous it's pretty hard to make a probe without one.

The OCTO-2 specifically, as the lightest probe core and the one that you'd probably use on anything that actually would mount an Ant in the first place, does not. Nor do lawnchairs, if you're building some kind of lightweight Kerbaled craft.

11 minutes ago, Superfluous J said:

Unless your probe core has reaction wheels, or you're using a Octo-2 for which the smallest reaction wheel and it combined are lower mass than all probe cores with reaction wheels.

Those would be the very supplemental control systems I am talking about. And their mass is poison for lightweight design.

The smallest reaction wheel has a mass of 0.05t and is, in addition to being way more control authority than something using an Ant could possibly need, shoots the TWR in the foot. A pair of Spiders provides twice the thrust at under two thirds the weight of an Ant + wheel combination. And doesn't need electrical power, to boot. The (slight) vacuum Isp difference is more than made up for by the weight savings on these kinds of microsats. This is even more true if you're going really lightweight and using a single Spider through the use of the translate tool.

Edited December 3, 2020 by foamyesque

[Superfluous J]

1 hour ago, foamyesque said:

Those would be the very supplemental control systems I am talking about. And their mass is poison for lightweight design.

The smallest reaction wheel has a mass of 0.05t and is, in addition to being way more control authority than something using an Ant could possibly need, shoots the TWR in the foot. A pair of Spiders provides twice the thrust at under two thirds the weight of an Ant + wheel combination. And doesn't need electrical power, to boot. The (slight) vacuum Isp difference is more than made up for by the weight savings on these kinds of microsats. This is even more true if you're going really lightweight and using a single Spider through the use of the translate tool.

All very true. It just depends though on what you consider essential in a design. Personally, the ability to turn the craft without running the engine is essential in most of my probes, and the cheapest way to do that is with an Okto-2 and the smallest reaction wheels. If I'm doing that anyway then an engine with gimbal isn't necessary, and the Ant is therefore the best choice. For you it's not, and therefore the Ant is useless.

I believe the philosopher Arnold Jackson* put it best, "Different strokes for different folks."

I wish you could turn down the reaction wheels' torque in the VAB and the mass would similarly decrease. But barring that, those are the best I'll get.

*You may know him for his more well known phrase, "What you talkin' 'bout, Willis?"

[king of nowhere]

 how can you not have attitude control on a ship? if you must point your rocket in one direction, and you are not and have no reaction wheels, are you going to turn on the rocket in the wrong direction and use gimbaling to eventually move it right? i can't believe this can work.

personally, since my light probes still need some kind of science capacity, i prefer to use the rgu; it has reaction wheels AND science container integrated, it's the lightest and least encombrant combination i can get of those 3 parts. If i need stronger reaction wheels and more battery, i use the hecs2.

 

speaking of command moduels, what about the QBE? 30 kg heavier than the okto2, same functionality. are there any reasons to use it where you would not be better off using an octo2?

Edited December 3, 2020 by king of nowhere

[foamyesque]

2 minutes ago, king of nowhere said:

 how can you not have attitude control on a ship? if you must point your rocket in one direction, and you are not and have no reaction wheels, are you going to turn on the rocket in the wrong direction and use gimbaling to eventually move it right? i can't believe this can work.

Yup. Can, have, and might well do so again. :p

I prefer to use something like RCS or torque wheels on larger craft, but on a tiny probe, you get by far the best attitude-control-for-mass from a gimballing engine. Went to orbit on 670kg that way :p

[king of nowhere]

2 minutes ago, foamyesque said:

 but on a tiny probe, you get by far the best attitude-control-for-mass from a gimballing engine. Went to orbit on 670kg that way :p

yes, that works for launch, but hope you never have to make manuevers again. i suppose you can do it for some relay satellites

[foamyesque]

1 minute ago, king of nowhere said:

yes, that works for launch, but hope you never have to make manuevers again. i suppose you can do it for some relay satellites

 

Nah, I've used it for orbital manouvers too. When you're that light you have all the dV in the world, if you want it. Nulling out any unwanted translation isn't difficult unless you're trying for extreme precision. This is especially so if you've got a pair of engines; you can roll trivially, toggle engines on and off with action groups, and flip end-for-end with just the barest puff of propellant and barely any translation.

You should try it sometime. It's a whole new way to fly.

 

[The rocket exploder]

14 hours ago, The Doodling Astronaut said:

I didn't even know it existed. So I nominate it as well

I love the ant engine, I use it time to time. Just doesn't make sense on the larger scale, but for gilly...

I have also never once used a drain valve

I really don't make small landers and almost never land at gilly. I don't use the drain valves either. Thought they were cool not that useful for me.

[Corona688]

16 hours ago, king of nowhere said:

 how can you not have attitude control on a ship? if you must point your rocket in one direction, and you are not and have no reaction wheels, are you going to turn on the rocket in the wrong direction and use gimbaling to eventually move it right? i can't believe this can work.

There was a kind of solid booster rocket they "shut off" by blowing a hole in the side to force a slow spin, which would make the thrust average out to zero over a long period of time.  It was used to boost satellites to a higher orbit.  If it's stupid and works...  it might still be stupid.  but also works.  sometimes.

[PaperAviator]

correct me if I'm wrong but pretty sure that the mk2 crew cabin and the hitchhiker storage container are both inferior in cost/kerbal and mass/kerbal to two mk1 business jet cabins

[Entropian]

I use the drain valve occasionally for high-performance LF-O SSTOs.  Draining the extra oxidizer is a nice method of increasing the range at the cost of a lower TWR.

[king of nowhere]

1 hour ago, PaperAviator said:

correct me if I'm wrong but pretty sure that the mk2 crew cabin and the hitchhiker storage container are both inferior in cost/kerbal and mass/kerbal to two mk1 business jet cabins

the mk2 part has excellent heat resistance, though, making it best suited for atmospheric reentry. as for the hitchhiker storage container, it is indeed inefficient, but i used it in many applications where i did not have mass problems because it looks good.

[IncompetentSpacer]

On 12/3/2020 at 2:00 AM, The Doodling Astronaut said:

I have also never once used a drain valve

Used it 10 seconds ago and thought of your comment. I had just not enough dv (bit under 100 ms) for insertion maneuver at kerbin and discovered it too late. There are several ways to solve this including abusing game mechanics but I did it using drain valve -dumped the mono-propellant onboard from one tank and it was more than enough. This is not a component I use a lot but I have it on each long journey mission.

Another use was earlier in my SSTO using rapier engines (among other things) -  I dumped oxidizer when returning to kerbin after kerbonaut rescue mission so that I could have most flying time  inside the atmosphere. Did not need it at the end since I had "perfect" entry and could glide to the airfield but still a valid example...

[Corona688]

22 hours ago, IncompetentSpacer said:

Used it 10 seconds ago and thought of your comment. I had just not enough dv (bit under 100 ms) for insertion maneuver at kerbin and discovered it too late. There are several ways to solve this including abusing game mechanics but I did it using drain valve -dumped the mono-propellant onboard from one tank and it was more than enough.

That's pretty clever -

- wait -

wait a moment.

Couldn't you have actually USED that fuel?  Burned it in RCS thrusters instead of just jettisoning?  Then you'd get even *MORE* delta V, losing the weight and getting actual thrust from it!

Jettisoning oxidizer sounds legit though.

Edited December 5, 2020 by Corona688

[IncompetentSpacer]

3 hours ago, Corona688 said:

Couldn't you have actually USED that fuel?  Burned it in RCS thrusters instead of just jettisoning?  Then you'd get even *MORE* delta V, losing the weight and getting actual thrust from it!

Jettisoning oxidizer sounds legit though.

True, especially if you don't have rule against reloading (and dont have other parallel missions which are doing their own intercepts while this crafts is on the way to its maneuver node).  The way I play burning RCS would be a guessing game - you are assuming that I knew that dumping propellant from one of the tanks would be enough and could make a plan based on that. My idea was to dump propellant from one tank and see on dV readout the effects of that and follow up with additional dumps if needed or think of something else if it had no effect.

Now the remaining RCS fuel will be used to reduce Pe once I achieve the orbit around Kerbal. Or whatever.

 

 

 

[Corona688]

4 hours ago, IncompetentSpacer said:

The way I play burning RCS would be a guessing game

It's really not.  Using fuel is always more effective than jettisoning it.  Period.  Full stop.  And it got used up irretrievably either way.

Edited December 6, 2020 by Corona688

[IncompetentSpacer]

14 hours ago, Corona688 said:

It's really not.  Using fuel is always more effective than jettisoning it.  Period.  Full stop.  And it got used up irretrievably either way.

Sorry, I don't see what you comment has to do with or that it addresses in any way broader context of my post.

 

[sturmhauke]

3 hours ago, IncompetentSpacer said:

Sorry, I don't see what you comment has to do with or that it addresses in any way broader context of my post.

You were talking about dumping monoprop to increase your dV for a maneuver. You could have also used it with your RCS system to help with the maneuver, which would have left you with more remaining dV overall. Unless you had monoprop but nothing that uses it, which is just bad design.

[IncompetentSpacer]

14 hours ago, sturmhauke said:

You were talking about dumping monoprop to increase your dV for a maneuver. You could have also used it with your RCS system to help with the maneuver, which would have left you with more remaining dV overall. Unless you had monoprop but nothing that uses it, which is just bad design.

How do you tell how much dv certain amount of monopropellant will produce in 41 ton spacecraft? Also do note that I do have rule of no-reload in this particular career (not when playing/experimenting  in sandbox obviously or when bugs cause some issues) as I thought I  indicated in first sentence in this post indirectly but perhaps should have done so more explicitly.  Maybe this is what is causing confusion.

If I dump fuel, see no effect, I can still orginize intercept from kerbin to save 3 kerbals. If I burn RCS for several minutes and see no desired effect then my options are reduced. Now if you reload whenever things go wrong - yep, than you can go back in time and try something else but as you can read above that is against my rules.

 

 

Edited December 7, 2020 by IncompetentSpacer

[razark]

2 hours ago, IncompetentSpacer said:

If I dump fuel, see no effect, I can still orginize intercept from kerbin to save 3 kerbals. If I burn RCS for several minutes and see no desired effect then my options are reduced.

If you dump the RCS fuel, you get nothing from it, aside from reduced mass.

If you burn the RCS fuel, then you get reduced mass, but also the dV from burning it.

In either case, you're out X units of RCS fuel, but one of them results in more dV.

 

2 hours ago, IncompetentSpacer said:

How do you tell how much dv certain amount of monopropellant will produce in 41 ton spacecraft?

Burn it and find out.  If your choices are "burn the fuel" or "jettison the fuel", burning it is going to give you more dV options for the same amount of fuel.

If you start burning it, and see no desired effect, then you stop burning it and use it for your other options.  If you dump some fuel and see no desired effect, would you continue dumping fuel in the hopes that something will change?

[vv3k70r]

On 12/5/2020 at 6:01 PM, Corona688 said:

Couldn't you have actually USED that fuel?  Burned it in RCS thrusters instead of just jettisoning?

I have same tought when read it.

8 hours ago, razark said:

In either case, you're out X units of RCS fuel, but one of them results in more dV.

Obvious.

 

[sturmhauke]

20 hours ago, IncompetentSpacer said:

How do you tell how much dv certain amount of monopropellant will produce in 41 ton spacecraft?

17 hours ago, razark said:

If you dump the RCS fuel, you get nothing from it, aside from reduced mass.

If you burn the RCS fuel, then you get reduced mass, but also the dV from burning it.

In either case, you're out X units of RCS fuel, but one of them results in more dV.

If you want exact numbers, you can either use a mod like KER to do the calculation for you, or you can do it yourself. See here for specifics:

Now, it's true that the dV produced by RCS is typically not very much, but if you're cutting it close it can mean the difference between a successful mission and a failed one.

[kerbiloid]

For example.

Soyuz dumps the remains of the RCS propellant after aerobraking to reduce mass on parachuting.

You can't predict exactly how much RCS propellant will the aerobraking take, so you have to have onboard more than your need,

[sturmhauke]

On 11/30/2020 at 10:29 AM, Bej Kerman said:

You transferred to Eve... So you used a transfer window.

That's not how the phrase "transfer window" is normally used. Generally it means "a period of minimal dV requirement to maneuver between two bodies", not "any possible maneuver between two bodies, regardless of dV cost". That's more like smashing through the wall because the window is too far away.

[Corona688]

On 12/6/2020 at 4:10 PM, IncompetentSpacer said:

How do you tell how much dv certain amount of monopropellant will produce in 41 ton spacecraft?

Say you have half a ton of monoprop aboard.  Plug 41, 40.5, and 240 ISP into http://www.strout.net/info/science/delta-v/  Meaning about 30m/s

[18Watt]

I nominate landing legs- all of them.

I gave up long ago trying to use landing legs, even just for aesthetic reasons.  They are plain too buggy.  My experience has been its always better to land on a structural part, or even just the engines, rather than the landing legs.  They are too bouncy, and once they settle down the ship will slide around on the surface- even a perfectly flat surface.

I wish that wasn’t the case.  I like the idea of thinking about how a vessel will absorb landing forces, and how it will sit on a surface without damaging components.   Sadly, it’s too frustrating to use them.   So I usually just land on my engines.