http://gallusrostromegalus.tumblr.com/post/158462684663/i-had-a-great-idea#notes - "What if aliens didn't require the constant touching that humans do?" Because as a species, we do require a lot of skin-to-skin touching! Especially as babies! It is a known issue for preemies, that they need physical contact and that the nurses sometimes have to make a call between stripping off the gloves and touching or refraining from removing the gloves, because it's so crucial for physical health. And in the SA medical stories thread, some nurses will admit "yeah, sometimes I strip off the gloves and make skin contact with patients if they're not sick with something contagious and awful, it really helps them a lot".
the worst part is when everything cracks perfectly but the last finger and you have the immediate urge to smack your hand with a hammer
aliens from heavier worlds could still get to space! the thing with needing a vehicle that's 97% fuel is that that only applies if the vehicle is supplying all the power. a third of a rocket's fuel is used to get it to the first 19% of its final speed, so by using something like a rocket sled, heavyworlders could still get to space.
There are a lot of factors, TBH, not just gravity but also the diameter of the world (this is really the biggest factor in orbital velocity), the atmosphere (if it's particularly thin, then you don't need to worry about drag as much, if it's particularly thick, you can reach higher speeds/altitudes with jet engines) etc. Also, heavyworld aliens could always resort to nuclear propulsion...
I'm now imagining, like. An Orion-type engine. But used for a takeoff. For when you've thoroughly fucked over your planet and need to leave it behind, I guess.
If you dig a big enough pit to launch from, it could work. I mean, it's still kind of stupid, but it could work. Or something like a hybrid jet/rocket engine, where you can run either atmosphere or internal remass past the reactor. Or even just a craft equipped with both jets and NTR. Or a just a high thrust NTR. The problem, basically, is that nuclear thermal rockets are generally low in thrust, especially when there's an atmosphere in the way. So you use the jet to reach a high enough altitude and speed that you can use the NTR to reach orbital velocity efficiently... Although, if the aliens are as danger-averse as they often seem to be in these things, they're unlikely to try it.
That might be more of a human level of recklessness in those settings, but one could imagine aliens making extensive use of the "Big Dumb Booster" concept, like the Sea Dragon. (I will never not be salty that, somewhere in an Aerojet Rocketdyne warehouse, there are detailed plans for this rocket and instructions to fucking mass-produce it, which will likely never be seen again because budget cuts.)
I'm honestly kinda thinking that in a setting where Humans Are Orks, it would be perfectly possible for the EM drive to be something that shouldn't work but does because humans think it works.
Even if it works as advertised, the EM drive produces too little acceleration to be useful in getting off the ground. Once you're in space? Hell yeah, it's awesome. But the thing has a 'thrust' comparable to ion drives, not exactly high performance.