Launch Vehicles:

To date, the only way to achieve the propulsive energy to successfully launch spacecraft from Earth has been by combustion of chemical propellants, although mass drivers may be useful in the future for launching material from the Moon or other small bodies.

There are two groups of rocket propellants, liquids and solids. Many spacecraft launches involve the use of both types of rockets, for example the solid rocket boosters attached to liquid-propelled rockets. Hybrid rockets, which use a combination of solid and liquid, are also being developed. Solid rockets are generally simpler than liquid, but they cannot be shut down once ignited. Liquid and hybrid engines may be shut down after ignition and conceivably could be re-ignited.

Expendable launch vehicles, ELV, are used once. The U.S. Space Transportation System, STS, or Shuttle, is a reuseable system. Most of its components are refurbished and reused multiple times.

A sampling of launch vehicles of interest to interplanetary mission follows. One measure of comparison among launch vehicles is the amount of mass it can lift to Geosynchronous Transfer Orbit, GTO.


Atlas II is a member of the Atlas family of launch vehicles which evolved from the successful Atlas intercontinental ballistic missile (ICBM) program. It is designed to launch payloads into low earth orbit, geosynchronous transfer orbit or geosynchronous orbit. Atlas IIA is a two-and-a-half stage vehicle, primarily used to support the Defense Satellite Communications System III program. The Atlas IIA is capable of lifting approximately 14,500 pounds (6,577 kilograms) into low earth orbit and 6,100 pounds (2,767 kilograms) to a geosynchronous orbit (22,000 miles-plus).

The Atlas II provides higher performance than the earlier Atlas I by using engines with greater thrust and longer fuel tanks for both stages. All three engines provide 494,500 pounds of total thrust capability. This series uses an improved Centaur upper stage - the world's first high-energy propellant stage - to increase its payload capability. Centaur propulsion is provided by a Pratt and Whitney liquid rocket engine set consisting of two engines that provide 41,000 pounds of thrust.

Atlas IIs are launched from Cape Canaveral Air Force Station, Fla., by the 45th Space Wing, and by the 30th Space Wing at Vandenberg Air Force Base, Calif. In May 1988, the Air Force chose General Dynamics (now Lockheed-Martin) to develop the Atlas II vehicle. The Atlas was originally fielded as an ICBM in the early 1960s. The Air Force replaced the Atlas ICBMs with Minuteman missiles and converted them into space launch vehicles in the late 1960s. NASA used the Atlas as a space launch vehicle as early as 1958. Atlas served as the launch vehicle for Project SCORE, the world's first communications satellite that broadcast President Eisenhower's pre-recorded Christmas message around the world. An Atlas booster carried U.S. astronaut John Glenn into orbit under Project Mercury, the first U.S. manned space program. Atlas space launch vehicles were used in all three unmanned lunar exploration programs. Atlas Centaur vehicles also launched Mariner and Pioneer planetary probes.

The Atlas launch vehicle is composed of three basic families: the Atlas II (IIA and IIAS), the Atlas III (IIIA and IIIB) and the Atlas V (400 and 500 series). The Atlas II family is capable of lifting payloads ranging in mass from 6,200 lb (2,812 kg) to 8,200 lb (3,719 kg) to geosynchronous transfer orbit (GTO). The Atlas III family is capable of lifting payloads up to 9,920 lb (4,500 kg) to GTO. The Atlas V family is capable of lifting payloads up to 19,100 lb (8,650 kg) to GTO.

The currently operational Atlas II family is operating with a 100% mission success rating, delivering 47 satellites to their proper orbits in the past seven years. Atlas IIAS has achieved 17 for 17 successful missions.


The Delta II is an expendable launch, medium-lift vehicle used to launch Navstar Global Positioning System (GPS) satellites into orbit, providing navigational data to military users. Additionally, the Delta II launches civil and commercial payloads into low-earth, polar, geo-transfer and geosynchronous orbits.

The Delta II stands a total height of 125.9 feet (37.8 meters). The payload fairing -- the shroud covering the third stage and the satellite -- is 9.5 ft wide to accommodate the GPS satellite. A 10-foot (3.3 meters) wide fairing also is available for larger payloads. Six of the nine solid-rocket motors that ring the first stage separate after one minute of flight, and the remaining three ignite, then separate, after burn-out one minute later.

The Delta launch vehicle family began in 1959 when NASA's Goddard Space Flight Center awarded a contract to Douglas Aircraft Company (now Boeing) to produce and integrate 12 space-launch vehicles. The Delta used components from the U.S. Air Force's Thor intermediate-range ballistic missile as its first stage and the U.S. Navy's Vanguard launch-vehicle program as its second. The first Delta was launched from Cape Canaveral Air Force Station on May 13, 1960 and had the ability to deliver a 100-pound spacecraft into geostationary transfer orbit.

In January 1987 the Air Force awarded a contract to McDonnell Douglas, now Boeing, now United Launch Alliance, for construction of 18 Delta IIs to launch Navstar GPS satellites, originally programmed for launch on the space shuttle. Since then, the order expanded to accommodate 28 GPS satellite-dedicated launch vehicles.

The first Delta II was successfully launched on Feb. 14, 1989, at Cape Canaveral. There are two primary versions of the Delta II (6925 and 7925). The Delta 6925, the first version, carried the initial nine GPS satellites into orbit. The Delta program has more than 245 successful domestic and foreign military and commercial launches. The Delta accomplished many firsts over the years. These include the first international satellite, Telstar I, in 1962; the first geosynchronous-orbit satellite, Syncorn II, in 1963; and the first commercial communications satellite, COMSAT I, in 1965. The Delta II is launched primarily from Cape Canaveral AFS, Fla., but is also launched from Vandenberg Air Force Base, Calif. Members of Air Force Space Command's 45th Space Wing, with headquarters at Patrick AFB, Fla., and 30th Space Wing at Vandenberg are responsible for the Delta II's military launch missions.

A larger medium-lift Delta-III has begun service, and a medium- to heavy-lift Delta IV family, whose liquid-propellant main engine burns liquid hydrogen and LOX, will enter service in the near future. In fact, Space Launch Complex 37 at the Kennedy Space Center (KSC), where Viking and Voyager began their journeys, has become the site for the new Delta-IV launch facility.

Delta Launch

Delta Explosion


The Titan IV is the largest unmanned space booster used by the Air Force. The vehicle is designed to carry payloads equivalent to the size and weight of those carried on the space shuttle. The Titan IV consists of two solid propellant motors, a liquid propellant two-stage core, and a 16.7-foot diameter payload faring. The system includes a cryogenic wide-body Centaur upper stage, and also may be flown with an Inertial Upper Stage, or no upper stage. Overall length of the system is 204 feet when flown with an 86-foot payload faring.

Titan IV consists of two solid-propellant stage "O" motors, a liquid propellant 2-stage core and a 16.7-ft diameter payload fairing. Upgraded 3-segment solid rocket motors increase the vehicle's payload capability by approximately 25%. The Titan IV configurations include a cryogenic Centaur upper stage, a solid-propellant Inertial Upper Stage (IUS), or no upper stage. Titan IV rockets are launched from Vandenberg Air Force Base, California, or Cape Canaveral Air Force Station, Florida. Titan IV launches from Launch Complex 40 at Cape Canaveral Air Force Station, Florida, and from Space Launch Complex 4E at Vandenberg Air Force Base, California. Titan IV core vehicle stages are built at Lockheed Martin's Titan manufacturing facility.

The first Titan IV B was successfully flown from Cape Canaveral Air Force Station on February 23, 1997. This configuration improves reliability and operability and increases lift capability by 25%. Advancements also include improved electronics and guidance. The Titan IV B has standardized vehicle interfaces that increase the efficiency of vehicle processing. Additionally, the more efficient programmable aerospace ground equipment (PAGE) is used to monitor and control vehicle countdown and launch.

The Titan IV Centaur is capable of placing 10,000-pound payloads into geosynchronous orbit, 22,300 miles above the Earth. The Titan IV system is also capable of placing 39,100 pounds into a low Earth orbit at 28.6 degrees inclination or 31,000 pounds into a low Earth polar orbit.

Titan Launch

Titan Explosion

The Solid Rocket Motor Upgrade, currently under development for Titan IV, will incorporate modern technology to provide increased performance and enhanced reliability. With SRMU, the Titan IV Centaur will be capable of placing 12,700-pound payloads into geosynchronous orbit and 47,800 pounds into a low earth orbit. SRMU production started in November 1993. The Air Force has contracted with Lockheed Martin to produce 41 Titan IVs by the end of fiscal year 1999. The contract, valued at more than $12 billion, was originally awarded to the former Martin Marietta Launch Systems Company in February of 1985. Titan IVs are launched from Launch Complex 40 and 41 at Cape Canaveral Air Station, Fla., and from Space Launch Complex 4E at Vandenberg AFB, Calif. The first Titan IV was launched June 14, 1989.

As of 2006, the Titan has been retired due to the expensive of its operation (high cost of hydrazine and nitrogen tetroxide, as well as the special handling techniques due to teir toxicity).


The Russian Soyuz launch vehicle evolved out of the original Class A ("Sputnik") ICBM designed by Sergei Korolev and his OKB-1 design bureau (now RSC Energia). From the early 1960's until today, the Soyuz launch vehicle has been the backbone of Russia's manned and un-manned space launch fleet. Today, the Soyuz launch vehicle is marketed internationally by a joint Russian / French consortium called STARSEM. As of August 2001, there have been ten Soyuz missions under the STARSEM banner.

The addition of the restartable Ikar upper stage to the three-stage Soyuz in 1999 allowed Starsem to launch 24 satellites of the Globalstar constellation in 6 launches. Following this success, Starsem introduced the flexible, restartable Fregat upper stage with significantly more propellant capacity than the Ikar, thus opening up a full range of missions (LEO, SSO, MEO, GTO, GEO, and escape).

In 2002, Starsem will introduce the Soyuz/ST, which adds increased payload volume (4.110-m fairing) and flexibility (digital control system) to this launch system and meets both the performance and payload accommodation needs of the customer. The Soyuz configuration introduced in 1966 has been the workhorse of the Soviet/Russian space program, achieving a high launch success rate in over 800 flights. As the only manned launch vehicle in Russia and the former Soviet Union, the Soyuz benefits from exacting standards in both reliability and robustness.

Soyuz/ESA Launch

The Samara Space Center continues to mass-produce the Soyuz in Samara, Russia, and has facilities dimensioned for the production of up to 4 launch vehicles per month. In fact, peak production of the Soyuz in the early 1980's reached 60 vehicles per year. As a result of continued demand from the Russian government, International Space Station activity, and Starsem's commercial orders, the Soyuz is in uninterrupted production at an average rate of 10 to 15 launch vehicles per year with a capability to rapidly scale up to accommodate user's needs.


The Pegasus is an air-launched (via a modified Lockheed L-101 I aircraft), three stage, all solid propellant, three axis stabilized vehicle. Manufactured by the Orbital Sciences Corporation, it is the small-class vehicle that DOD will used following the last Scout launch in 1994. The Pegasus-XL vehicle, a "stretched" version of the original Pegasus vehicle, can place a 400 to 1,000 pound payload into low-Earth orbit.

During a typical flight, the launch aircraft is maneuvered to a predetermined site safely out of range of any populated area. The aircraft climbs to an altitude of 38,000 feet and the Pegasus-XL is released from the belly of the L-101 1. The Pegasus-XL begins an unpowered descent at a rate of approximately 60 feet-per-second while the first-stage arms and prepares for ignition. Forward velocity of Pegasus during the descent is the same as the launch aircraft or Mach 0.8, which is approximately 524 miles per hour.

After 5 seconds in free fall, stage-one's solid rocket motor, manufactured by Hercules Aerospace, fires and burns for approximately 71 seconds. The Pegasus 22 foot, delta-shaped wing begins to produce lift as the Pegasus accelerates, and the launch vehicle begins a 2.5 g-force pull-up. As Pegasus climbs, the booster experiences maximum dynamic pressure (Max-q) of approximately 1,200 pounds per square foot approximately 30 seconds after first-stage ignition. (For comparison, on a typical space shuttle launch, Max-q is equal to approximately 600-700 pounds per square foot.)

The second stage Hercules solid fuel motor ignites about 1 minute 35 seconds into the flight at an altitude of 37 miles and at approximately 2 minutes, the payload fairing is ejected. The second stage flies to an altitude of approximately 129 miles with a velocity of over 12,000 miles per hour. At the appropriate altitude to achieve the designated orbit, the third stage Hercules motor ignites and burns for 1 minute and 6 seconds to place its payload into orbit.

Zenit/Sea Launch:

The Zenit launch vehicle was first introduced in 1985 but was not announced to the world until 1989. The Zenit is a highly automated two stage LOX / RP (kerosene) vehicle originally designed to place large (10 metric tonne) spy satellites into LEO polar orbits. The Zenit's highly automated launch system and large payload capability, as well as its ability to launch in all types of weather, made it the ideal launch vehicle for the Sea Launch International Consortium.

Currently, there are two Zenit configurations, the two stage Zenit 2 and the three stage Zenit 3SL. The Zenit 3SL uses an NPO Energomash Block DM third stage to transfer satellites into high altitude orbits. Currently, two and three stage Zenit launches are conducted out of Baikonur. The Sea Launch Co. operates the Zenit 3SL from a floating platform in the South Pacific to service the GTO market.

The Assembly & Command Ship serves as a rocket assembly factory, while providing the mission control facilities and crew and customer accommodations for 240 people during sea-based launches. The ship was built at the Govan Shipyard in Glasgow, Scotland, and Kvaerner Maritime a.s. is the Sea Launch partner.

In the fall of 1997, the ship sailed for Russia where special equipment for handling rocket segments and for command and control was installed and tested. It arrived in Long Beach on July 13, 1998. The vessel is 660 feet long, 106 feet wide and has a cruising range of 18,000 nautical miles.

The launch platform from which the Sea Launch rockets will be launched was once a North Sea oil drilling platform. Odyssey was refurbished at the Rosenberg Shipyard in Stavanger, Norway, and Kvaerner Maritime a.s. is the Sea Launch partner. Sea Launch says the vessel is the largest semi-submersible, self-propelled craft of its kind in the world.

The platform provides living accommodations for 68 crew and spacecraft team. Odyssey features a large, environmentally controlled hangar for storage of the rocket during transit, and with mobile transporter/erector equipment that is used to roll out and erect the rocket prior to fueling and liftoff. Special facilities onboard also provide storage of the kerosene and liquid oxygen rocket propellants. Odyssey is 436 feet long and 220 feet wide.


The Proton K launch vehicle is used as a three-stage vehicle primarily to launch large space station type payloads into low earth orbit and in its four-stage configurations to launch spacecraft into high-energy (geosynchronous transfer, geosynchronous and interplanetary) trajectories.

The Proton K is capable of placing approximately 19,760 kg (46,999 lbm) into low earth orbit (LEO) at 51.6 degrees and between 4,700 kg (10,362 lb) and 4,930 kg (10,868 lb) to GTO. 1,880 kg (4,630 lbm) can be placed directly into GSO.

In a typical Proton launch, the vehicles six first-stage engines ignite 1.6 seconds before liftoff. Stage two ignition occurs approximately two minutes into flight, four seconds prior to jettison of the first stage. Stage three vernier engine ignition occurs at 330 seconds, with separation of the second and third stages taking place 3.5 seconds later. The stage three main engine ignition occurs 2.5 seconds after separation. The payload fairing is jettisoned late in the ascent, at 351 seconds. The stage three shut-down occurs at approximately 570 seconds, with the stage three and four separation occurring approximately 15 seconds later.

For typical Proton missions, the first three stages inject the elements above the third stage into a 200-kilometer (108-nautical mile) circular orbit. The Block DM fourth stage then performs all mission unique maneuvers, starting from the parking orbit. The first burn of the Block DM engine occurs approximately 55 minutes after lift-off as the vehicle crosses the first ascending node, and lasts six and one half minutes. The second Block DM burn, which places the spacecraft into its final orbit, occurs approximately 5.5 hours later at geosynchronous altitude, and lasts two and one half minutes.

Space X:

Space Exploration Technologies Corporation (SpaceX) is an American aerospace manufacturer and space transport services company with its headquarters in Hawthorne, California, USA. It was founded in 2002 by former PayPal entrepreneur and Tesla Motors CEO Elon Musk with the goal of creating the technologies to reduce space transportation costs and enable the colonization of Mars. It has developed the Falcon 1 and Falcon 9 launch vehicles, both of which were designed from conception to eventually become reusable, and the Dragon spacecraft which is flown into orbit by the Falcon 9 launch vehicle to supply the International Space Station (ISS) with cargo. A manned version of Dragon is in development.

Falcon 9 is a family of two-stage-to-orbit launch vehicles, named for its use of nine engines, designed and manufactured by SpaceX. The Falcon 9 versions are the Falcon 9 v1.0 (retired), Falcon 9 v1.1 (retired), and the current Falcon 9 full thrust, a partially-reusable launch system. Both stages are powered by rocket engines that burn liquid oxygen (LOX) and rocket-grade kerosene (RP-1) propellants. The first stage is designed to be reusable, while the second stage is not. The three Falcon 9 versions are in the medium-lift range of launch systems. The current Falcon 9 ("full thrust upgrade") can lift payloads of at least 13,150 kilograms (28,990 lb) to low Earth orbit, and at least 5,300 kilograms (11,700 lb) to geostationary transfer orbit. Full payload capacity is kept private, and may vary depending on whether the first stage follows a reusable or expendable flight profile.

Launch Sites:

If a spacecraft is launched from a site near Earth's equator, it can take optimum advantage of the Earth's substantial rotational speed. Sitting on the launch pad near the equator, it is already moving at a speed of over 1650 km per hour relative to Earth's center. This can be applied to the speed required to orbit the Earth (approximately 28,000 km per hour). Compared to a launch far from the equator, the equator-launched vehicle would need less propellant, or a given vehicle can launch a more massive spacecraft.

A spacecraft intended for a high-inclination Earth orbit has no such free ride, though. The launch vehicle must provide a much larger part, or all, of the energy for the spacecraft's orbital speed, depending on the inclination.

For interplanetary launches, the vehicle will have to take advantage of Earth's orbital motion as well, to accommodate the limited energy available from today's launch vehicles. The launch vehicle is accelerating generally in the direction of the Earth's orbital motion (in addition to using Earth's rotational speed), which has an average velocity of approximately 100,000 km per hour along its orbital path.

In the case of a spacecraft embarking on a Hohmann interplanetary transfer orbit, recall the Earth's orbital speed represents the speed at aphelion or perihelion of the transfer orbit, and the spacecraft's velocity merely needs to be increased or decreased in the tangential direction to achieve the desired transfer orbit.

The launch site must also have a clear pathway downrange so the launch vehicle will not fly over populated areas, in case of accidents. The STS has the additional constraint of requiring a landing strip with acceptable wind, weather, and lighting conditions near the launch site as well as at landing sites across the Atlantic Ocean, in case an emergency landing must be attempted.

Launches from the east coast of the United States (the Kennedy Space Center at Cape Canaveral, Florida) are suitable only for low inclination orbits because major population centers underlie the trajectory required for high-inclination launches. High-inclination launches are accomplished from Vandenberg Air Force Base on the west coast, in California, where the trajectory for high-inclination orbits avoids population centers. An equatorial site is not preferred for high-inclination orbital launches. They can depart from any latitude.

Complex ground facilities are required for heavy launch vehicles, but smaller vehicles such as the Taurus can use transportable facilities. The Pegasus requires none once its parent airplane is in flight.

Launch Windows:

A launch window is the span of time during which a launch may take place while satisfying the constraints imposed by safety and mission objectives. For an interplanetary launch, the window is constrained typically within a number of weeks by the location of Earth in its orbit around the sun, in order to permit the vehicle to use Earth's orbital motion for its trajectory, while timing it to arrive at its destination when the target planet is in position. The launch window may also be constrained to a number of hours each day, in order to take advantage of Earth's rotational motion. One example is a vehicle launching from a site near the Earth's terminator which is going into night as the Earth's rotation takes it around away from the sun. If the vehicle were to launch in the early morning hours on the other side of the Earth, it would be launching in a direction opposite Earth's orbital motion.


  • What are the advantages to a wide array of different launch vehicles?
  • What was the Pegasus launch system?
  • What is the SeaLaunch system?