I have a cast of (human) characters that crash land their spaceship on a planet that is still in "the dark ages," and the people there (also human) are amazed by the strange newcomers and their technology. The problem is there is absolutely no way they would speak the same language. Except that I can think of absolutely no way to make the story and still respect that element of reality.

There are processes already developed for learning new languages, too. Unless these are the first aliens your people have ever encountered, I'm sure they have some sort of software along to aid them cracking a new language, even weird ones like ones based on clicks, or tail postures, or ultra-high frequencies that the human ear can't hear (or vice versa).

Just let it work itself out for your characters. It can even be fun for the reader watching them try to communicate. You could show that going on then skip a few months ahead to where they have a working understanding of the aliens' language. A few misconceptions thrown in can also make the storyline take some unexpected turns.

But, to be honest, I don't see why they'd have such a dilemma from the start. Think of how the Dutch first communicated with the Japanese when they made contact. The two languages are vastly different, they don't even use the same alphabet much less the same sentence structure, and there is really nothing to relate to vocabulary wise.

In retrospect, I like to think we regret that.

I think the stronger group will force itself on the weaker one, language and all--unless it has strong principles like those to which Star Trek's Enterprise crew aspire.

A scoiety could be in the dark ages yet stronger than advanced aliens, depending on how good the locals are with swords, and the aliens' skill with, and willingness to use, advanced weapons.

So if the group who crash land their spaceship feel strong, they make the locals learn English. If they are weak, they learn the local lingo--politely, without making waves.

You could have the (alien) characters speak a pidgin form of English, garbled and distorted and maybe mispronounced and misspelled, in the early scenes, while the (human) characters try to communicate with them...then let it go as the story progresses and the (human) characters get a better grip on the (alien) lingo. [I'm thinking Barry B. Longyear's "Enemy Mine" here as an example]

I'd be reluctant to use some kind of software / computer / universal translator thingy...besides being all done to death in hundreds of stories (and "Star Trek"), the ones that exist do an exceptionally poor job of the job. [Now I'm thinking of all those Japanese instruction manuals translated (by computer) into English.]

You might try differentiating the human-alien dialog in some way, like speaking in third person or being exceptionally formal or archaic, while any human-human dialog descends into more colloquial modes of speech. (This thought's my own, though I'm sure somebody somewhere must have done it.)

If you don't want to make an issue of it and don't want any kind of automated translated (vat grown Language Acquisition Device, etc) then maybe you make your aliens telepaths? Otherwise the astronauts might be stuck learning the local language the hard way.

I just recently read the Rama series by Arthur C. Clarke and the last of the four books has an extensive part (co-authored by Gentry Lee now that I'm thinking of it) where the protagonists/point of view characters end up embedded with an alien culture and have to learn how to communicate with them. It's hard for the humans to understand the aliens, who basically speak in color. The aliens, conveniently, can read lips. Gets around that side of it...and made for some really interesting stuff. You might want to pick up the book - I think it's called Rama Revealed (though it's best read as the fourth in the series. However, to be honest, they're dense books written in a pretty heavily descriptive style with omni or 3rd person limited shallow immersion - it's a little odd to read at first and took longer for me to read and absorb, but I did really enjoy them. Your mileage may vary.)

It's all about willing suspension of disbelief. If the premise is interesting, we'll read on despite it being incredible. (I love the Firefly TV series despite the characters firing guns inside space ships!)

If it's an issue you feel must be addressed, then I agree that babel fish devices are cliched. If this is the first alien civilsation they've ever met, and this is a first contact story, it would be an interesting issue to address.

But if it's not the story's central issue, you'll need a short cut. Maybe they could have one or two linguistic psychologists aboard with a theory of developing mutual understanding and language quickly, and their theory works.

My understanding is that it's all about recognising common concepts and giving them names, so maybe they use dozens of flash cards with pictures of common items and actions. Or maybe they observe the natives, and take photos of common items and actions--with permission and after assuring them the cameras don't take away their souls ;-) Then, they sit around with the natives sharing food and giving names to items and actions, maybe English names, maybe local names, whichever works best--but mostly English names so that we readers can understand what's happening.

People who teach English as a foreign language do it this way, through pictures, and without translating into local language, so perhaps borrow some of their ideas. I believe that by using such techniques you can get from zero understanding to enough for survival quite quickly--understanding local literature would take a lot longer but would probably not be necessary for the purposes of the story.

Perhaps, too, they could concentrate on learning enough common language to deal with their mutual problem. That's what they'd do for real, right? You don't want to spend too much story time on this problem, and neither do your characters, so let them take the short cuts necessary--like, only learning enough to do the job.

Hope this helps,
Pat