Even if I try desperately, it might still be futile.
I heard that my grandfather went to the war front prepared to die.
"Captain, I really need to return to Mars. I left my iPhone there," he said desperately.
Your future consists of certain death. How would you feel in this situation? Probably very frantic and desperate.
Another translation for this word is simply certain death, though I'd rather you learn one of the first two before this one if you can.
The readings are the on'yomi readings, though 必 (ひつ) gets shortened to ひっ. In your desperate situation just imagine that you're trying to get out of it, and to do so you move the つ only to find a smaller っ blocking your way. It is certain death.