what are ant engines good for?

[Sweetnsaltyish]

I've been playing the game for a while, and i've never quite understood the purpose of the ant and spider engines.

[Aegolius13]

Ants are very useful for really small craft like relay satellites.  Despite the mediocre ISP, they get pretty good delta-v on small stuff due to their low dry mass.  And then you have a very light final stage that's easy to put behind a Spark stage.  

Spiders are pretty useful as vernier thrusters on a Reliant- or Dart-powered launch stage, kinda like the Soviet/Russian R-7 rockets.  Cheaper and (to my mind) more effective than using fins to steer.  I guess they could also be useful if you have a really small spacecraft that needs to keep the rear node free, like for a docking port, but that's not a common situation. 

(Also, welcome aboard!)

[klesh]

Welcome to the Forums, Sweetnsaltyish!

 

Edited February 26, 2019 by klesh
Added forum welcome

[JacobTheFoxx]

I personally use them for all of my communication sattelites, especially for ones that require high accuracy, their low thrust helps with that. It's also good for small command chair ships.

[Snark]

1 minute ago, JacobTheFoxx said:

I personally use them for all of my communication sattelites, especially for ones that require high accuracy, their low thrust helps with that.

^ This.  Especially handy for dialing in that last, little tiny bit of orbital adjustment when you're trying to precisely synchrononize an orbit (either geosynchronous, or synchronous with another satellite).  If you're OCD like I am and want to nail the orbital period down, literally to the millisecond, then the teeny thrust really helps for that.

[farmerben]

 

This is a little Tylo lander I made.  All the engines fire at the same time, and 5 stages decouple as their fuel runs out.  There is an ant motor in the center.  The toroids decouple one by one.  The decouplers have crossfeed enabled, and the fuel flow priorities are set to drain from bottom to top.  

Edited February 26, 2019 by farmerben

[Tyko]

I use them all the time. They're so lightweight and they're available fairly early in the tech tree. I'll often use clusters of 2, 3 or 4 of them also.

 

[linuxgurugamer]

5 minutes ago, Tyko said:

I use them all the time. They're so lightweight and they're available fairly early in the tech tree. I'll often use clusters of 2, 3 or 4 of them also.

Same here.  It's amazing the amount of Dv you can get with an Ant and a T400 tank

[klesh]

11 minutes ago, Tyko said:

I use them all the time. They're so lightweight and they're available fairly early in the tech tree. I'll often use clusters of 2, 3 or 4 of them also.

 

 

Indeed!  This is one of the reasons a 1.25m Engine Plate is essential, especially with the new bare variant editions coming up.  Clusterability to the max! 

 

If you are reading this and feel the same way, add your vote!

https://bugs.kerbalspaceprogram.com/issues/21314

[Espatie]

I use 5 Ant engines on my ultralight Mun lander. At 2.573t (including 3 Kerbals in the seats, 2 KIS containers packed with SEP gear and an Experiment Storage Unit) it packs 1204 m/s vacuum delta-v with a TWR in Munar gravity of 2.34 when fully fueled.

[Stone Blue]

I also use them on my comm sats. I was noticing that when I inserted comsats into final orbit, spending lots of time thrusting back and forth prograde/retrograde with RCS thrusters to get really accurate orbits, which is a PIA... after getting a "perfect" orbit, using just RWs to reorient radial from prograde, the orbits would change.

Finally, instead of two or three RCS thrusters oriented along prograde/retrograde on the sat, I just started placing one Ant radially, placed so while thrusting, the sat would be oriented radial/anti-radial. so I could adjust final orbit with the sat already oriented properly. Adjusting the thrust down to ~5%-10%, is less thrust than what I was doing with RCS, and allowed for much finer orbit adjustments, with out all the hassle.

[Tyko]

1 hour ago, Espatie said:

I use 5 Ant engines on my ultralight Mun lander

Here's my 1 Ant Ultra-light lander   

[Aegolius13]

2 hours ago, Espatie said:

I use 5 Ant engines on my ultralight Mun lander. At 2.573t (including 3 Kerbals in the seats, 2 KIS containers packed with SEP gear and an Experiment Storage Unit) it packs 1204 m/s vacuum delta-v with a TWR in Munar gravity of 2.34 when fully fueled.

Would you come out ahead using 5 Ants instead of a Spark?  The latter would be the same mass but higher thrust and ISP, I think.

[Espatie]

5 minutes ago, Aegolius13 said:

Would you come out ahead using 5 Ants instead of a Spark?  The latter would be the same mass but higher thrust and ISP, I think.

It's a matter of mission profile. Because the Landers mass balance changes significantly if Cargo or Kerbals aren't being carried, on such a lightweight frame the ability to dial back some of the engines in order to keep the thrust balance even is very useful indeed.

[Tyko]

11 minutes ago, Espatie said:

19 minutes ago, Aegolius13 said:

Would you come out ahead using 5 Ants instead of a Spark?  The latter would be the same mass but higher thrust and ISP, I think.

It's a matter of mission profile. Because the Landers mass balance changes significantly if Cargo or Kerbals aren't being carried, on such a lightweight frame the ability to dial back some of the engines in order to keep the thrust balance even is very useful indeed.

Yep...Also landers actually need a certain amount of TWR to land safely.

I think that the deciding factor for orbital ships is the ratio of engine mass to total vehicle mass...The heavier the vehicle the less engine mass matters and the more that ISP matters. Not sure of the cutoff point.

[Espatie]

As I said, if all engines are at full blast it has a TWR in Munar gravity of 2.34. by the time it lands this is usually more like 3 due to fuel use.

[Stone Blue]

2 hours ago, Aegolius13 said:

Would you come out ahead using 5 Ants instead of a Spark?  The latter would be the same mass but higher thrust and ISP, I think.

A thing to consider in this case is rate of fuel consumption/economy. Which means you may be able to save on tank &/or resource mass.

[farmerben]

5 hours ago, Aegolius13 said:

Would you come out ahead using 5 Ants instead of a Spark?  The latter would be the same mass but higher thrust and ISP, I think.

I agree with Aegolius on this one.  If the throttle control is not sensitive enough, then the whole vessel is way overpowered.  The only reason I can think of to prefer 5 ants over a spark is the radial attachment feature.   Using 4 or 6 ants in the radial configuration doesn't use up the precious top and bottom node.  I really like to put docking ports on my top and bottom nodes.

[I_Killed_Jeb]

Like others here I used it for my mini-pollo build I did for fun, using the mk-1 capsule as the mk-3 equivalent and scaling everything from there.

 

[Chel]

They're useful for small craft and on larger craft for pushing away from a recently separated stage. As I've said before, every part has it's uses, however big or small it may be

[Aeroboi]

• Small re-entry vessels. A Mk1 pod with a FL-T100 and a Ant has a TWR of 0.15. That isn't much but for small re-entry vessels or for orbital surveys where thrust isn't a issue it's a good thing. On top of that, some people create small toroidal tank vessels with a command seat on top. A spark or Twitch here would be to much.
• On that ground using a Ant will conserve overall delta V due to less dry mass. A spark on the other hand has a TWR of 1.36 with a ISP of 5 seconds higher. Ultimately the Ant has almost 200dv more and when you do not need high thrust on a upper stage the less powerful spark is a much better option. Consequently smaller satellites would be better equipped using a Ant or Spark.
• Retro thrusters. Sometimes I put engines in a cargo bay as reverse thrusters. Sometimes the craft is very small and a Ant is a better solution then a full equipped RCS system. IMO docking can be done without use of rcs due to the ridiculous magnetic effect of the docking ports. A reverse thruster may come in handy if your aproach is to fast and you don't want to roll all over again to get the aproach right. It's still more hassle then with a fully equipped rcs system but better then just having a rear engine for forward motion.
• I also made a LFO/ION hybrid SSTO Moho orbiter for a crew of 3. Normally these orbiters are in the 6.5-7.5 Ton region using only LFO. Using a combination of Dawn electric engines and Ant I get more TWR with more Delta-V for just over 5 Ton compared to a heavier LFO only orbiter plus I can refuel the leftover Xenon to the mothership when getting back to Kerbin plus it makes the orbiter to get the lander to Moho lighter because the orbiter is lighter.

The only obstruction is that you takeoff and land within sunlight and that the thrust is low so that you have to properly pilot navigate to a precise landing spot

Craft File: https://www.dropbox.com/home?preview=MOHON.craft

Edited February 27, 2019 by Aeroboi

[RizzoTheRat]

I tend to use Spiders or Twitch's for communications satellites where I'll usually send up a stack of 3 or 4 satellites in a single launch so I want to keep the length down. 

For some reason I'd always thought the Ant was only base mounted and hadn't realised it could be radially mounted.  As it has a better vacuum ISP than the Spider I'll be switching to Ants instead!  That does seem to make the Spider a redundant though, it's only benefit is the better atmospheric ISP, but where are going to use something with that little thrust in atmosphere?  Except...

19 hours ago, Aegolius13 said:

Spiders are pretty useful as vernier thrusters on a Reliant- or Dart-powered launch stage, kinda like the Soviet/Russian R-7 rockets.  Cheaper and (to my mind) more effective than using fins to steer.  I guess they could also be useful if you have a really small spacecraft that needs to keep the rear node free, like for a docking port, but that's not a common situation. 

...I wasn't aware that you could this either, is there a setting on the engine to have it under RCS control instead of Throttle control? 

[Aegolius13]

1 hour ago, RizzoTheRat said:

...I wasn't aware that you could this either, is there a setting on the engine to have it under RCS control instead of Throttle control? 

Not RCS.  But they will work with SAS or manual steering,  just like a normal engine with gimbal.

[Fraston]

The Ant is good for Vacuum mini-probe-landers and tiny satellites.

The Spider has gimbal and infinitely better ASL thrust, and I use it on tugs for tiny space station parts.

 

[Elroy Jetson]

I am amazed at all the intricacies and variety this game offers and I read threads like this and as a new player I sit here and say, "Oh, I want to build one of those, and that one, and that is cool, and how did they do that, I want to try that!"  Slow down guys, give me a chance to catch up!