All night long the Martians were hammering and stirring, sleepless, indefatigable, at work upon the machines they were making ready, and ever and again a puff of greenish-white smoke whirled up to the starlit sky.
showing sustained enthusiastic action with unflagging vitality; "an indefatigable advocate of equal rights"; "a tireless worker"; "unflagging pursuit of excellence"
Incapable of being fatigued; not readily exhausted; unremitting in labor or effort; untiring; unwearying; not yielding to fatigue; as, indefatigable exertions, perseverance, application
You use indefatigable to describe someone who never gets tired of doing something. His indefatigable spirit helped him to cope with his illness = untiring, tireless + indefatigably in·de·fati·gab·ly She worked indefatigably and enthusiastically to interest the young in music. determined and never giving up (Early indéfatigable, from indefatigabilis, from fatigare; FATIGUE)