NASA - National Aeronautics and Space Administration

Rocket Basics
A rocket is a vehicle that contains everything needed to place a payload into space. A payload can be people, a satellite or other equipment. A rocket in its simplest form is a tube holding a gas that is packed under pressure. A small opening at one end of the tube allows the gas to escape. When the gas escapes, it gives a thrust, or push, that propels the rocket in the opposite direction. Modern rockets use a propellant. Propellant is a mixture of fuel and a chemical called an "oxidizer" that gives off oxygen. The fuel and oxidizer burn together and produce rocket thrust.

People have been sending rockets into space for more than 50 years, starting with the launch of the Soviet Union's Sputnik I in 1957. The technology of basic rocketry is nearly 2,000 years old. The first device known to use rocket propulsion was built between 428 and 347 B.C.

The concepts are still the same, but rockets have evolved considerably. Innovative technologies, new materials and improved engineering practices, along with lessons learned from past experience, influence the evolution of rockets.

Apollo Program
The Apollo Program had the ambitious goal of sending humans to land on the moon, then returning them safely to Earth. To achieve this goal, NASA used technology from previous rockets and developed new technology. On July 20, 1969, Apollo 11 was the first spacecraft to meet the goal. Apollo 11 was a spacecraft that flew on top of a Saturn V (5) rocket. Apollo 11 consisted of three parts -- the Service Module, the Command Module and the Lunar Module. The Saturn V was a three-stage rocket made of more than three million parts. A staged rocket fires several engines or sets of engines. The first stage lifts the rocket off the pad. That stage then falls away as the second-stage engines ignite to carry the remaining rocket to an even higher altitude.

Space Shuttle Program
Even before Apollo 11 carried humans to the moon, NASA was already planning the space shuttle as a way to allow humans to remain in space. The space shuttle is the only spacecraft capable of delivering and returning large payloads and scientific experiments to and from space. The space shuttle usually orbits around Earth about 200 miles up. It can go higher than that, but it cannot leave Earth orbit, which is necessary to travel to the moon. The shuttle is the world's first reusable spacecraft and consists of three main components: the two white solid rocket boosters, the orange external tank and the orbiter. The solid rocket boosters are reusable. They are ejected from the shuttle system about two minutes after liftoff. They use a parachute to land in the ocean. A ship retrieves them, and they are prepared to use for another launch. The external tank is ejected from the orbiter about eight minutes after launch. As it falls back to Earth, it burns up in the atmosphere. Each of the space shuttle orbiters -- Atlantis, Discovery and Endeavour -- was designed for a life of at least 100 missions.

Constellation Program
Currently, NASA has scheduled the last space shuttle launch for 2010. Following the last scheduled mission, the shuttle will be retired. NASA is working on new spacecraft for America's next generation of rockets, called the Constellation Program. With launches no sooner than 2015, Constellation spacecraft will be able to make trips to the International Space Station and will one day go to the moon. Constellation components are:

• Ares I (1) rocket
• Ares V (5) rocket
• Orion crew exploration vehicle
• Altair lunar lander

Ares I and Orion will take crews to the space station. Just as the Apollo spacecraft rode atop the Saturn V rocket, Orion will ride atop the Ares I, which is also called the crew launch vehicle. Unlike the Saturn V rocket used during the Apollo era, the Constellation Program will use two rockets for a mission to the moon. When astronauts are to travel beyond Earth's orbit, Altair and the necessary cargo will ride on the huge Ares V. After both rockets have been launched, the astronauts in the Orion crew capsule will dock with the part of the Ares V called the Earth departure stage and the Altair for the trip to the moon. Ares I will be like a car or SUV that carries the crew to space. Ares V, also known as the heavy-lift vehicle, will be like an 18-wheeler that carries the lunar lander and other equipment.

Comparison of Space Vehicles

	Saturn V	Space Shuttle	Ares I	Ares V
Height	363 ft. (111 m) As tall as a 36-story building	149.6 ft. (45.6 m) As tall as a 15-story building	325 ft. (99 m) As tall as a 32-story building	381 ft. (116 m) As tall as a 38-story building
Weight	6.69 million lb (3 million kg)	4.4 million lb (2 million kg)	2 million lb (907,000 kg)	8.2 million lb (3.7 million kg)
Payload	260,150 lb (118,100 kg)	53,700 lb (24,360 kg)	56,200 lb (25,000 kg)	413,807 lb (187,699 kg)
Number of Astronauts	Up to 3 astronauts	Up to 7 astronauts	4 to 6 astronauts	Not applicable
Location of Astronauts	In capsule on top of third stage	In orbiter attached to side of launch vehicle	In crew vehicle on top of second stage	Not applicable

Current design plans for Constellation vehicles could change.


New Missions, New Rockets
When the shuttle retires after almost 30 years, NASA will need a new spacecraft that can accomplish many goals. The next generation of spacecraft in the Constellation Program will meet the challenge. Constellation will have three missions:

• Service the space station -- take crew to the station, stay up to 180 days and return crew to Earth
• Seven-day mission to the moon
• Six-month lunar outpost

Constellation will do some of what the space shuttle has done plus what Apollo has done, and more.

The space shuttle cannot go to the moon. The shuttle does not carry enough propellant to go beyond Earth’s orbit. Also, the space shuttle is designed to land like an airplane. The moon does not have an atmosphere to allow the shuttle to land as it is designed. The shuttle is designed for re-entry from an Earth orbital speed of 17,500 mph -- not the 25,000 mph speed of a moon mission. Entering Earth's atmosphere at this high speed would destroy the shuttle.

For trips to the moon, the new missions require more than the Apollo missions could accomplish. Apollo was limited to landing near the moon's equator. The new spacecraft will carry enough propellant so that the Altair lunar lander will be able to land anywhere on the moon's surface. The new Orion spacecraft also will allow four people to go to the lunar surface instead of two as in the Apollo missions. The Orion spacecraft can operate without a crew in lunar orbit, unlike Apollo, which required one astronaut to remain in orbit while the other two explored the moon’s surface. And crews will be able to stay on the moon longer. The Apollo 17 crew currently holds the record for staying on the moon for almost 75 hours. At first, the Orion crew will be able to stay for four to seven days. But once a lunar outpost is established, crews could remain on the lunar surface for as long as six months.

Heritage Hardware
Parts of the Constellation Program use heritage, or legacy, hardware. This is the name given to the parts of the new spacecraft that are derived from an existing spacecraft. The Ares rockets will use technology designs from both the Apollo and Space Shuttle programs. Ares V will also use upgraded RS-68 engines from the Delta IV (4) rockets used for NASA satellite launches. Designing new rockets takes less time if engineers borrow and upgrade spacecraft parts and technologies that are already proven to work on other rockets. Engineers know that these technologies are reliable and safe.

From the Apollo-Saturn missions, the Constellation Program will use:

• The J-2/J-2S engine, now J-2x
• The Orion capsule shape from Apollo

Heritage hardware from the space shuttle includes:

• Solid rocket boosters
• The liquid oxygen/liquid hydrogen core from the external fuel tank
• An aluminum lithium tank alloy
• First-stage avionics system

Other Lessons Learned
Besides using heritage hardware, NASA also has learned better ways to build the new spacecraft. NASA has learned better ways to keep astronauts safe by studying the Apollo and Space Shuttle programs.

The computers NASA uses now for missions are much smaller and more powerful than the computers used for Apollo missions. Your cell phone has more computing power than the computers used during the Apollo era.

The Constellation Program will take the best of what NASA has learned in more than 50 years of exploration to build safe spacecraft that will be able to lift more mass and go farther than any other human mission.

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More About Apollo, Space Shuttle and Constellation
> Apollo
> Space Shuttle Basics
> What Is the Space Shuttle?
> The Amazing Space Shuttle
> Steps to Countdown Storybook
> Constellation and Space Shuttle Fact Sheets
> Constellation Program Main Page
> What Is Ares?
> What Is Orion?
> What Is Altair?
> Ares Launch Vehicles Main Page
> Orion Crew Vehicle Main Page
> Constellation: Earth, Moon, Mars Interactive

Ares Lithographs
>  NASA's Ares Projects (PDF, 3.2 MB)
>  Ares V Cargo Launch Vehicle (PDF, 1.3 MB)
>  Building for the Future (PDF, 1.9 MB)
>  Rockets and Racecars (PDF, 3 MB)