The Dead-Star Rover

Only savage engines roamed that arid world, charging one another with snarling guns beneath those grinding treads. And two puny machine-less humans like Torcred and Ladna should die quickly. That they suddenly could become the most dangerous things alive must surely be some dead god's joke.
The terrapin was traveling eighty miles an hour—far too fast for such uneven country. Over maddeningly repetitive dunes it scudded, rising with a swoop to each windward slope and hurtling clear of the ground beyond each wave-like crest, to plunge through the trough in a hurricane of flying sand.
The wiry little man who crouched tensely, hugged by a padded safety belt, in the pitching, vibrant interior of the midget combat car, was impatient, furiously so. Thanks to an unusually stubborn case of engine trouble, he was a full two hours behind the rest of his troop; by now they must have sighted the new camping place on the shore of the Salt Sea. And the blazing sun was already sinking toward the dusty horizon haze. Torcred the Terrapin came of a people unused to fear—but his shrewd intelligence, calculating the risks he must run before he rejoined the others, found the daylight dangers enough and to spare, and nothing attractive in the thought of an encounter with any of the things that prowled the desolate plain after the sun went down.
So the terrapin fled at reckless speed westward over the dipping dunes, and Torcred's deepset irongray eyes, squinting against the glare that even the polarized glass in the narrow vision slits could only cut down, were anxious. Under his breath he chided his own nervousness; probably after all nothing would happen....
Midway in the thought it did happen, and with almost catastrophic suddenness. The black silhouette of a flying thing materialized out of the sun's glare, diving straight at him. It flattened out and was gone overhead, while the roar of its passing echoed behind it. And the terrapin had rocked to the impact of bullets all the more fiercely driven by the aero's terrific velocity; its armor rang and steel splinters hummed like wasps inside it.