My sympathies, but all is not lost. Like other people who have worked in FT or similar trades such as yours I've had my share of manoeuvring heads-in, and as you've noticed, it's not desperately pleasant. (It could be worse, I had a boss who'd spent 160hrs in the observers seat of a Sea-Vixen when he worked at de-Havilland's flight test department. That is worse, the thing is buried in the bowels of the jet, with just an 8" square skylight!).
It can be coped with, and you should eventually aclimatise to it. But, in the meantime:-
- Keep cool, don't overdress, if you are slightly chilly, you'll suffer much less than if you are comfortably warm. (Of course, survival issues may get in the way here, depending upon the nature of operations).
- As far as your duties permit, look outside the cockpit, at identifiable objects.
- Don't let yourself just sit there, keep doing things. If there's no job to do invent one (just don't bother the pilot with it!).
- Try to keep yourself in a flow of fresh air so far as possible, any smell of fumes can really knock you down.
- And finally, anti-seasickness pills help a-lot whilst you get aclimatised. They got me through two sorties a day of flying back-seat for spinning trials some years ago with no ill effects, and if you talk to the pharmacist about your particular needs, you can get ones that don't impair your performance or create any other risk.
G