Journey Through Orbital Mechanics Quiz

Answer: The minimum inclination of his orbit is 28.5°

The inclination of an orbit is the angle of the rocket's path from the Equator. The location of a launch pad has a big effect on the trajectory. Without performing any complicated fuel costly maneuvers, the orbit must pass over the latitude of the launch site once per orbit. Therefore, the minimum inclination is the launch site latitude.

Answer: False

The term zero gravity is a misnomer. Gravity is the only force pulling on an orbiting object. Being in orbit is basically free-falling. Rocky is falling due to gravity, but his horizontal velocity is such that he never lands.

Answer: Ellipse

Kepler's First Law states "The orbit of a planet is an ellipse with one star at its focus." In orbital mechanics, a circle, a parabola, and a hyperbola are all forms of elliptical orbits, with varying eccentricity. A hyperbolic orbit is a high energy orbit, and allows rockets to travel past the gravitational influence of the body.

When the Apollo astronauts were travelling to the Moon, they were in a hyperbolic orbit. A parabolic orbit means the orbiting object has the minimum amount of energy to escape, or escape velocity.

A circular orbit is an ellipse with zero eccentricity.

Answer: Rocky travels faster the closer he is to Earth

While in a single orbit, the closer you are to the object you are orbiting, the faster you go.

Answer: Hohmann Transfer

A Hohmann Transfer is the simplest maneuver to reach a higher altitude and uses the least amount of fuel, but takes a long time to complete.

Answer: All of these are true

Geostationary Orbit is where a lot of communications satellites reside. Since they orbit the Earth every 24 hours, they appear to hover over one spot on the Equator, giving maximum coverage over a desired area. The altitude can be derived from Kepler's 3rd Law.

Answer: They take the same amount of time

According to Kepler's Third Law, the period of an orbit, or the amount of time it takes to travel one complete orbit, does not depend on mass. The square of the period is directly proportional to the cube of the semi-major axis.

Answer: The first time, launching at 9 km/s

A higher delta V places an object in a higher altitude, but according to Kepler's Third Law, the higher the altitude, the longer it takes to complete an orbit. It's counterintuitive, but launching with a lower initial speed allows an object to travel around Earth in less time. In order to escape Earth's gravitational pull, the minimum escape velocity is 11.3 km/s.

Answer: Hyperbolic

According to Kepler's First Law of Planetary Motion, a planet's orbit is an ellipse with the Sun at one focus. A lunar gravitational slingshot is simply a hyperbolic orbit, with the Moon at one focus. Though they have very different shapes, a hyperbola can be defined as an ellipse with an eccentricity greater than 1. For an orbital eccentricity less than 1, a spacecraft would never be able to escape the gravitational field of its orbiting body.

Answer: 5, Lagrangian Points

The five Lagrangian Points are of special interest to the scientific community, since the Sun and the Earth always appear in the same relative locations due to the interaction between gravity from both the Sun and Earth. L1 is a point in space aligned between the Sun and the Earth.

It has a smaller orbital radius than the Earth, but because of Earth's gravitational influence they have the same period. Currently, the Solar and Heliospheric Observatory, or SOHO, is orbiting at L1. L2 is on the same line, but is beyond Earth.

In this case, Earth's gravity causes a shorter orbital period. L3 is in the same orbit as Earth, just 180° apart. This has been the subject of science fiction, since if a planet existed there, we would never be able to detect it since it would be forever blocked by the Sun. L4 and L5 are at opposite 60° angles between the Sun and Earth, also on the same orbit as Earth.