Mission to Mars

The inbound trip

[ The outbound trip ]

In planning a realistic mission to Mars one must consider the amount of fuel required, the size of the rocket required, the length of time required for the entire journey and the physical needs of the crew.

Consideration of these factors, and the current technology available to accomplish this mission, dictate that only a free-flight (ballistic) trajectory to Mars is possible. This requires a very precise alignment of Mars and the Earth at launch time (called the "launch window") so that as the spacecraft "coasts" through space it converges on the planet Mars.

A practical mission is outlined in the diagrams below.

On all diagrams of the solar system all the planets orbit the Sun in a counter-clockwise direction (as seen looking down on the Earth's North Pole).
The images are not drawn to scale.
The relative positions, travel times, and trajectories of the Earth, Mars, and the imagined spacecraft, are approximately correct for a real Mars mission.
Multiple images on each diagram indicate the apparent motion of Mars and the Earth during the mission.
Red arrows indicate the flight path of the spacecraft.

Sun symbol

Earth symbol

Mars symbol

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550 Days on Mars
Working and Living in a Closed Environment.

The green (curved) arrow shows the motion of the Earth around the Sun during the crew's stay on Mars.

The orange (curved) arrow shows the motion of Mars around the Sun during the crew's stay on Mars.

The Crew has been on Mars working, exploring, relaxing, and awaiting the launch window which will allow them to return to earth.
During this time they have been living in a sealed habitat, growing their food and manufacturing the air and water they need to survive.
After 550 days on Mars, the planets are aligned to permit a (relatively) fast return to Earth. The flight path home ( and hence the launch date) has been pre-determined by the type of rocket and the amount of rocket fuel available for the return mission.

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Day 730
Blast off for home.
Once safely off Mars' surface the only way to get home from Mars is to reduce your orbital speed around the Sun. Therefore the rocket is fired "backwards" with respect to Mars' orbital motion. This reduces the spacecraft's velocity and it begins to "fall" inward towards the Sun.
Mars slowly seems to pull away from the returning spacecraft even though the spacecraft is moving in the same direction as Mars. Launching "backwards" (called a retrograde launch) only slows down the spacecraft a little, it still moves in the same direction as Mars.

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Day 775
"Falling" Sunward.
Very gradually the distance between Mars and the spacecraft increases, as the path of the returning ship turns inward towards the Sun.
Just as a roller coaster car accelerates as it drops downwards and picks up speed, so does the returning spacecraft as it "falls" downwards towards the Sun.

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Day 820
Picking up speed.
Once again Mars appears to be getting closer but this time it appears off to one side of the spacecraft.
The speed of the ship is increasing rapidly as it hurtles inwards and crosses the Earth's orbital path. This is the fastest the crew has travelled in the entire journey, but it will get even faster as they approach their "lowest" point close to the orbit of Venus.

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Day 865
Maximum Speed.
The gravitational pull of the Sun speeds up the spacecraft and also causes its path to curve around the Sun. It will begin heading back out towards the Earth's orbit.
From now on the spacecraft is moving "uphill" against the Sun's gravity. Even though it is now slowing down, it is still moving very fast and will "catch" the Earth in few short weeks.

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Day 910
Welcome Home Crew!
During the last few weeks the crew has been stowing their Mars samples, organizing their on-board equipment and checking last minute navigational details to ensure a safe landing.
The crew has been gone 910 days (about two and one half years).

[Home]

Prepared by the YES I Can! Science Team,
Faculty of Pure and Applied Science, York University

Transparency Master	Day 730 Blast off for home. Once safely off Mars' surface the only way to get home from Mars is to reduce your orbital speed around the Sun. Therefore the rocket is fired "backwards" with respect to Mars' orbital motion. This reduces the spacecraft's velocity and it begins to "fall" inward towards the Sun. Mars slowly seems to pull away from the returning spacecraft even though the spacecraft is moving in the same direction as Mars. Launching "backwards" (called a retrograde launch) only slows down the spacecraft a little, it still moves in the same direction as Mars.
Transparency Master	Day 775 "Falling" Sunward. Very gradually the distance between Mars and the spacecraft increases, as the path of the returning ship turns inward towards the Sun. Just as a roller coaster car accelerates as it drops downwards and picks up speed, so does the returning spacecraft as it "falls" downwards towards the Sun.
Transparency Master	Day 820 Picking up speed. Once again Mars appears to be getting closer but this time it appears off to one side of the spacecraft. The speed of the ship is increasing rapidly as it hurtles inwards and crosses the Earth's orbital path. This is the fastest the crew has travelled in the entire journey, but it will get even faster as they approach their "lowest" point close to the orbit of Venus.
Transparency Master	Day 865 Maximum Speed. The gravitational pull of the Sun speeds up the spacecraft and also causes its path to curve around the Sun. It will begin heading back out towards the Earth's orbit. From now on the spacecraft is moving "uphill" against the Sun's gravity. Even though it is now slowing down, it is still moving very fast and will "catch" the Earth in few short weeks.
Transparency Master	Day 910 Welcome Home Crew! During the last few weeks the crew has been stowing their Mars samples, organizing their on-board equipment and checking last minute navigational details to ensure a safe landing. The crew has been gone 910 days (about two and one half years).