Following the Apollo 11 mission, four other American missions successfully put astronauts on
the Moon. The last manned mission to the moon was Apollo 17, which landed on December
11, 1972. To date, no other country has put a person on the Moon.
In July 1975, the Soviet Union and the United States carried out a joint mission called
the Apollo-Soyuz Test Project. During the mission, an American Apollo spacecraft docked
with a Soviet Soyuz spacecraft, as shown inFigure23.24. Many considered this to be the
symbolic end of the Space Race.
Figure 23.24: The docking of an Apollo spacecraft with a Soyuz spacecraft in 1975 was a
symbolic end to the Space Race. ( 8 )
Exploring Other Planets
Both the United States and the Soviet Union also sent probes to other planets during the
Space Race. Aspace probeis a spacecraft that is sent without a crew to collect data by
flying near or landing on an object in space, such as a planet, moon, asteroid, or comet. In
the Venera missions, the USSR sent several probes to Venus, including some that landed on
the surface. The U.S. sent probes to Mercury, Venus, and Mars in the Mariner missions, and
landed two probes on Mars in the Viking missions.
In the Pioneer and Voyager missions, the U.S. also sent probes to the outer solar system,
including flybys of Jupiter, Saturn, Uranus, and Neptune. The Pioneer and Voyager probes
are still traveling, and are now beyond the edges of our solar system. We have lost contact
with the two Pioneer probes, but expect to have contact with the two Voyager probes until
at least 2020.
Lesson Summary
- Rockets have been used for warfare and ceremonies for many centuries.
- Newton’s third law explains how a rocket works. The action force of the engine on the
gases is accompanied by a reaction force of the gases on the rocket.