What obstacles did john Glenn face?

What is the origin of large craters on earth? What is better to find a tornado with. radar or aneroid barometer? How do scientist learn from their observations? How do astronauts stay on the Moon's surface? Which main sequence stars are most massive? What was the Fujita scale based on and why? Which planet is closed to the sun? Where would people see if they traveled to earth? Why do you still list indigo as a color in the rainbow? What equipment does a rocket carry? What order are the planets? Why would on object that weighs 294 newtons on earth weigh only 50 newtons on the moon? What year did the space shuttle fly? Why any watch shows 10.10 am time? Why Do astronauts cannot hear each other on the moon? How many planets does Earth have? What is the atmosphere of Jupiter made of? What was the highlight of Apollo 1? Why did Apollo 13 have landing problems? How many earths in the sun?