What shall we do with the O-10 "Puff" engine?

[Stoney3K]

With the "Fore by Throttle" option on RCS blocks, the "Puff" Monopropellant engine has become obsolete. It's equally (or less) powerful than an RCS port while the RCS ports can do the exact same thing.

Is there even a need for a Monopropellant-fueled engine now that the RCS blocks can do the same? Maybe it should be buffed or scaled up so it can be used as a service engine on larger craft?

I feel like an engine that is more powerful than the Puff could be of use for shuttles or interplanetary spacecraft, but it should be considerably larger.

Your thoughts?

[ferrer]

The wiki says that the Puff engine has a thrust in vacuum of 20 kN and weighs 90 kg, whereas the most powerful RCS port has a thrust of only 2 kN and weighs 30 kg. What makes you say that the Puff is less powerful?

[Red Iron Crown]

Puff has better Isp and TWR than RCS thrusters, it still has a place in monoprop-only craft.

[Dire_Squid]

I've used 4 Puff engines to slow my descent AND land on Dunian soil, in 1.0 and 1.1

 

They work fine, for me.

Edited May 8, 2016 by Dire_Squid

[Stoney3K]

At least, something bigger than the Puff for a Monopropellant engine would be nice. We've got the Mk2 and Mk3 Monoprop tanks which can hold a massive amount of fuel, but the engines that are designed for it are so tiny that they look and act completely out of scale. They're sensible enough for smaller craft, but we've got no equivalent for the big stuff right now.

If you have a 30-50 ton Mk3 spacecraft you're not gonna push it around with two Puffs adding up to 40kN of thrust. Because that's going to take forever.

[mk1980]

the way I see it, the only advantage of monoprop engines is that the monoprop tanks are shorter than equivalent amounts of LF/O tanks. that's a very small niche considering that you pay a heavy tax for it (terrible Isp). i think i used them once in >400 hours of KSP and i regretted it. would make more sense to make the puff useful before they add a larger version of it, IMO.

[MaxL_1023]

They are more useful in modded setups, especially when realfuels is involved. Kerolox and Hydrolox suffers from boiloff and the engines have limited ignitions - in those case the puff burns storables and is a restartable engine. 

[Alshain]

I like to use it as a Shuttle OMS.

[Sereneti]

Monopropelant , Hydrazin, has the best Volum/energy ratio...
the puff-engine is ok, maybee a little more tech in the monopropelant-tree
(like a "normal-mountet" monopropelant-engine, )
 

[Stoney3K]

4 hours ago, Alshain said:

I like to use it as a Shuttle OMS.

The craft file also reveals that it was "intended" as a Shuttle OMS, but I find it to be too small and underpowered to be useful for an Mk3-sized shuttle.

The "real" Shuttle OMS is sized similarly to the Thud. I would have to check the actual thrust and Isp values for the OMS, though.

[Warzouz]

I don't use it much, but I had when I used to play with tugs for building space stations. I find it quite well. Sure it's not efficient, but it's a monoprop engine...

[FlyingPete]

It's useful for space station tugs, as the thrust and ISp are higher than for the RCS blocks. You can then keep the actual RCS thrusters to a sensible amount which helps with control. They're also handy for minimalist landing craft for low-gravity bodies. The inbuilt monopropellant capacity in the command pods sometimes increases the TWR enough to make them more efficient than the smaller LFO engines.

Stick a couple on a command module too, and when you run out of fuel, they can form a 'backup propulsion system' that can sometimes be just enough to get the lone capsule on a reentry trajectory.

 

I seem to recall the O-10 engine originally being considerably larger for use as an OMS.

[Wjolcz]

I find it to be an alright engine, though I wouldn't mind if it got a new model.

[Brofessional]

I use it all the time for tugs when assembling stations/motherships.

True it's not the most efficient, but it simplifies things by allowing my tugs to share a single RCS tank instead of bringing RCS+LFO tanks.

[Alshain]

On 5/10/2016 at 3:28 AM, Stoney3K said:

The craft file also reveals that it was "intended" as a Shuttle OMS, but I find it to be too small and underpowered to be useful for an Mk3-sized shuttle.

The "real" Shuttle OMS is sized similarly to the Thud. I would have to check the actual thrust and Isp values for the OMS, though.

But it works fine as a Mk2 shuttle OMS.

[MaxL_1023]

It is not that bad for orbital maneuvering for Mk 3 crafts either - usually those maneuvers are under 50 m/s of delta-v. A TWR of more than 0.25 or so is really not needed in real situations unless you are making Geostationary,  TLI or Escape burns. The shuttle itself only had a few hundred m/s available after reaching orbit - more than enough to deorbit or change PE/AP by hundreds of KM. It is only plane changes that are expensive.