Using tiny engines to get a big payoff

[JadedStoner]

So I fiddling around in game today and remembered Scott Manley saying something about the little Rocomax radial engines have a huge TWR, so I wondered if I could use em to get a probe into orbit. As it turns out, it wasn't so hard and I ended up with a little more than 2k deltaV in a 100km LKO.

Mods being used are KW Rocketry, MechJeb2 and Kethane (the smaller detector looks sweet)

[ComradeGoat]

They do, but their efficiency is even worse than the Mainsail, so you only really get any useful efficiency gain from them on really tiny stuff. If you are heavy enough to use lots, an LV-909 is likely to be better all round, I would think.

[magnemoe]

They do, but their efficiency is even worse than the Mainsail, so you only really get any useful efficiency gain from them on really tiny stuff. If you are heavy enough to use lots, an LV-909 is likely to be better all round, I would think.

Using an 180 liter tank and an typical probe payload, iso mapsat, small kertane detector and science parts you get the around 4200 m/s dV from two 24-77 and 4400m/s from the 909. the LV-N gives 4300.

If you go down to an 90 liter tank, the 24-77 win with 3400m/s while the 909 gives 3150 m/s.

Going up to 270 liter and the LV-N start to win with 5700 against 5400.

One benefit of the 24-77 is that it's nice on landers and skycranes, one flat 2.5 meter tanks and 2-6 engines and you are set.

[rkman]

the little Rocomax radial engines have a huge TWR

That's engine TWR, but what matters in terms of over all efficiency and delta-V is vessel TWR, where engine TWR is only one of several factors.