Lab+Protocol+2


 * Tensile Strength**

Introduction:

A Space elevator is an elevating device that consists of a cable and a couterweight that is in space. For a space elevator to operate, the cable must have a fairly constant length, meaning that the counterweight the cable is attached to should stay over one location relative to the earth (see diagram). Thus the space elevator has the same rotational period as the earth. For this to occur, the counterweight must be a specific height over the equator so that the rotational plane of the space elevator is parallel to that of the earth and the magnitudes of the centripetal force and gravitational pull of the centre of mass of the device are equal. On Mars, the circular region around the equator where the centre of mass of a space elevator must be located is known as the Areostationary orbit. The Areostationary orbit is approximately 17000 km above the equator.

A space elevator can be used to transport humans, supplies and resources from an orbiting spacecraft or spacetation to the surface of a celestial body. It can also be used to conduct experiment in different atmospheric levels of a planetary body. Space elevators are currently not feasable on Earth. The acceleration due to gravity on Earth is much higher than on Mars while the rotational periods are almost equal. This means that tensional forces on the space elevator cable would be significantly higher on earth than on mars. While no known material can withstand these tensional forces on earth, a space elevator on Mars is not only feasable, but has been proposed and can be built using current materials and technology.

To determine a suitable cable that can whithold the space elevator is an important aspect. The tension that would result in the rope and the rope's strength must be heavily evaluated before used on a device such as a space elevator. The cable should be both light so it may reduce tension but also strong so it may withstand tension. Therefore the best cable would have the biggest strength per the smallest unit of mass.

The tensile strength of materials can be tested using a Tensile Strength Tester Machine (TSTM) or a Uniaxial Tensile Test. This machine will record the maximum force required before necking occurs in the material. Necking is the strain a material can withstand when it begins to deform.

Research Questions Which material would be best used as a cable to withhold the space elevator?

Hypothesis

Methods

Assessment Force until breaking (N) Radius of cable (m) Area of cross section (m^2) Yield Strength Mass/unit Volume (Pa) Stainless Steel Nylon Kevlar Aluminum Copper Polyethylene Polyester Rubber Nickel Silk Paper Graphite Carbon fibre Your own 1 Your own 2 Your own 3 Cotton

Assessment

Resource List