Direct ascent is a method of landing a

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

on the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

or another

planetary surface A planetary surface is where the solid or liquid material of certain types of astronomical objects contacts the atmosphere or outer space. Planetary surfaces are found on solid objects of planetary mass, including terrestrial planets (including ...

directly, without first assembling the vehicle in Earth orbit, or carrying a separate landing vehicle into orbit around the target body. It was proposed as the first method to achieve a crewed lunar landing in the United States

Apollo program The Apollo program, also known as Project Apollo, was the United States human spaceflight program led by NASA, which Moon landing, landed the first humans on the Moon in 1969. Apollo followed Project Mercury that put the first Americans in sp ...

, but was rejected because it would have required developing a prohibitively large

launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...

Apollo program

The

was initially planned based on the assumption that direct ascent would be used. This would have required developing an enormous

, either the Saturn C-8 or Nova rocket, to launch the three-man

Apollo spacecraft The Apollo spacecraft was composed of three parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth. The expendable (single-use) spacecraft ...

, with an attached landing module, directly to the Moon, where it would land tail-first and then launch off the Moon for the return to Earth. The other two options that

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

considered required a somewhat smaller launch vehicle, either the Saturn C-4 or C-5. These were Earth Orbit Rendezvous, which would have involved at least two launches to assemble the direct-landing and return vehicle in orbit; and

Lunar Orbit Rendezvous Lunar orbit rendezvous (LOR) is a process for landing humans on the Moon and returning them to Earth. It was utilized for the Apollo program missions in the 1960s and 1970s. In a LOR mission, a main spacecraft and a lunar lander travel to lunar or ...

(LOR), which carried a smaller two-man

lunar lander A lunar lander or Moon lander is a Lander (spacecraft), spacecraft designed to Moon landing, land on the surface of the Moon. As of 2024, the Apollo Lunar Module is the only lunar lander to have ever been used in human spaceflight, completing s ...

spacecraft for flight between lunar orbit and the surface. LOR was the strategy used successfully in Apollo. The

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

also considered several direct ascent strategies, though in the end they settled on an approach similar to NASA's: two men in a

Soyuz spacecraft Soyuz () is a series of spacecraft which has been in service since the 1960s, having made more than 140 flights. It was designed for the Soviet space program by the Korolev Design Bureau (now Energia). The Soyuz succeeded the Voskhod spacecraf ...

with a one-man LK lander. The Soviets attempted to launch the N1 rocket on 21 February and 3 July 1969, both of which failed, before NASA's

Apollo 11 Apollo 11 was a spaceflight conducted from July 16 to 24, 1969, by the United States and launched by NASA. It marked the first time that humans Moon landing, landed on the Moon. Commander Neil Armstrong and Lunar Module pilot Buzz Aldrin l ...

lifted off and made the first crewed

lunar landing A Moon landing or lunar landing is the arrival of a spacecraft on the surface of the Moon, including both crewed and robotic missions. The first human-made object to touch the Moon was Luna 2 in 1959. In 1969 Apollo 11 was the first cr ...

on 20 July 1969. The Soviets would make two more attempts to launch the N1, in 1972 and 1974, but neither was successful. The Soviet engineering firm

OKB-52 NPO Mashinostroyeniya () is a rocket design bureau based in Reutov, Russia. During the Cold War it was responsible for several major weapons systems, including the UR-100N Intercontinental ballistic missile and the military Almaz space station ...

continued to develop the UR-700 modular booster for the direct ascent LK-700 ship.

Science fiction Science fiction (often shortened to sci-fi or abbreviated SF) is a genre of speculative fiction that deals with imaginative and futuristic concepts. These concepts may include information technology and robotics, biological manipulations, space ...

movies such as '' Rocketship X-M'' and '' Destination Moon'' have frequently depicted direct ascent missions, although the first was a two-stage vehicle which accidentally, and successfully landed on Mars, but failed to successfully return to Earth (crashed in Nova Scotia), and the second was a single-stage vehicle which successfully landed on the Moon, and speculatively returned to Earth (return not shown).

References

{{DEFAULTSORT:Direct Ascent Spaceflight concepts Apollo program

Apollo program

See also

References