Home > Sub-orbital spaceflight

The sub-orbital spaceflight should not be confused with a partial orbital spaceflight: a low Earth orbit, with deorbiting after less than one full orbit, as in the Fractional Orbital Bombardment System.

1 Overview

During freefall the trajectory is part of an elliptic orbit as given by the orbital equation. The perigee distance is less than the radius of the Earth, hence the ellipse intersects the Earth. The major axis is vertical, the semi-major axisIn geometry, the semi-major axis (also semimajor axis a applies to ellipses and hyperbolas. Ellipse The semi-major axis of an ellipse is one half of the major axis running from the center, through a focus, and to the edge of the ellipse. The major axis is is more than one half of the radius of the Earth, and almost always less than the radius.

If the objective is just to reach space, sub-orbital flights are appealing because this is very much easier (it simply means going higher than the edge of space) than to achieve orbit (which requires a velocityVelocity (symbol: v is a vector measurement of the rate and direction of motion. The scalar absolute value ( magnitude) of velocity is speed. Velocity can also be defined as rate of change of displacement or just as the rate of displacement, depending on of about 8 km/s (18,000 mph)). A dedicated sub-orbital spacecraft can therefore be built and operated much more cheaply than an orbital spacecraft. Less powerful sub-orbital craft may not reach speeds much higher than around 1.1 km/s to 1.3 km/s (2,500-3,000 mph).

However, for intercontinental ballistic space flights, like that of an ICBM, or a possible future commercial spacecraft, a typical speed is / might be 7 km/s.

For more information on the difference between sub-orbital and orbital spaceflightAn orbital spaceflight (or orbital flight) in the general sense is a spaceflight where the spacecraft reaches the height of, and through having an appropriate velocity enters into, orbit around an astronomical body. Most commonly the term is applied specis, refer to the article Difference between sub-orbital and orbital spaceflightsThere sometimes appears to be confusion among the general public about the difference between sub-orbital and orbital spaceflights . This article is an attempt to clarify this issue. It also elaborates on the technical implications of the differences betw.

2 Flight profiles

While there are a great many possible sub-orbital flight profiles, it is expected that some will be more common than others.

2.1 Tourist flights

Sub-orbital tourist flights will initially focus on attaining the altitude required to qualify as reaching space. The flight path will probably be either vertical or very steep, with the spacecraft landing back at its take-off site.

The spacecraft will probably shut off its engines well before reaching maximum altutude, and then coast up to its highest point. From the point when the engines are shut off to the point where the craft begins to slow its descent for landing the passengers will experience weightlessnessWeightlessness is the experience (by people and objects) during freefall, of apparently having no weight. This condition is also known as microgravity (see below). Weightlessness is not due to an increased distance to the earth; the acceleration due to gr.

In 2004, a number of companies worked on vehicles in this class as entrants to the Ansari X Prize competition. SpaceShipOne was officially declared by Rick Searfoss to have won the competition on October_4, 2004 after completing two flights within a two week period.