Robots explore delicate worlds partly because people cannot be sterilised
A robotic probe can be scrubbed clean before launch so it does not seed another world with Earth microbes. A human cannot, since each of us carries countless microorganisms that no suit reliably contains. That, along with cost, risk, crushing heat on Venus, fierce radiation near Jupiter and sheer distance, is why machines do most exploring.
Robotic craft also skip the heavy life support people need. Apollo's Moon landings required the Saturn V, costing more than a billion dollars a launch in today's money, while probes can ride smaller, cheaper rockets. Between them, probes have now visited every planet and Pluto, and the Parker Solar Probe dips into the Sun's chromosphere at its closest approach. Five are on their way out of the Solar System entirely: the two Voyagers, the two Pioneers and New Horizons.
Crewed flight is a much smaller club. As of 2026 only the Soviet Union and Russia, the United States and China have flown people. Yuri Gagarin's Vostok 1 made the first orbit in 1961, and Alan Shepard's Freedom 7 followed that year with a suborbital hop of just over 187 kilometres. China's Shenzhou first carried a crew in 2003. Almost every returning crewed orbital craft has been a capsule; the only winged exceptions were the Space Shuttle and the Soviet Buran, which flew once, uncrewed.
Before orbit came altitude. A V-2 climbed to 189 kilometres in June 1944, well past the 100-kilometre Karman line used to define spaceflight, while Sputnik 1 later circled the planet every 96.2 minutes at about 29,000 kilometres an hour. Most orbital spacecraft are never recovered, though agencies increasingly favour reusable designs such as SpaceX's Dragon.
The workhorses rarely make headlines. Automated cargo ships have hauled food, propellant and supplies to stations since 1978, and as of 2026 Progress, Dragon 2 and Cygnus keep the International Space Station stocked. Space telescopes, starting with OAO-2 in 1968, escape the blurring and light pollution that hamper ground observatories.
Source: Spacecraft
