NASA has started using things called CubeSats to explore space. These extremely small crafts are cheap and light, offering new opportunities for space exploration. CubeSats also help NASA explore the physics of space.
One advantage of CubeSats is that NASA can launch many of them. It is much more expensive to launch traditional spacecrafts, which are very expensive to make and use a lot of costly fuel. CubeSats, however, can be just a few centimeters big and can launch much more cheaply. This has opened up new opportunities for learning in space. A CubeSat can have a volume on 10cm3 and mass of 1.3kg.
Newton’s laws of motion have a huge impact on how CubeSats and other spacecraft operate when they leave the Earth. In space, the CubeSats don’t have much force working against them. So as soon as they start moving along a straight line, they will tend to just continue moving along that straight line indefinitely. In space, the force of friction is missing and can not slow down the CubeSats when they are moving in a certain direction. This applies if the CubeSats move in three dimensions as well as along a straight line. In space, the crafts can move in any direction and will continue moving in that direction because of Newton’s first law.
Newton’s second law says that if you exert the same force on two objects of different mass you will get different accelerations. The mass of the CubeSats is very small, 1.3kg. If force is max times acceleration (F = m a), then the momentum of the CubeSats should change based on their mass. Newton’s third law has more to do with what is happening in space, though, as it says that every action will have an equal and opposite reaction. In space, this means that crafts will move the opposite direction of their exhaust fuel. If fuel (A) exerts a force in one direction, the craft (B) will move in the opposite direction through space.
All of Newton’s laws effect motion in space. One factor of motion is velocity. In the context of physics, velocity is not just speed; it is a vector meaning both the speed something is moving at and the direction it is moving in. So the velocity of a CubeSat would depend on the force of the fuel it used to propel it and the direction in which it was propelled. One of the issues facing CubeSats is this system for propulsion. CubeSats have difficulty with accuracy when trying to photograph or record things in space. This comes from not having a precise way of moving around in three dimensions in space. One potential solution is to convert electrical energy into kinetic energy. This would work with Newton’s laws to create an opposing force that comes from charged particles pushing one while while momentum takes the CubeSat the other way.
The challenges of moving in space include more than propulsion. There are also issues when rigid bodies like CubeSats try to rotate. Usually, f = m a, but when rotation comes into play, there is torque to consider. The question is how much rotational inertia an object in space will have. Rotational inertia is how much the object will resist torque. In space, this is not much. As mentioned before, there is no friction to slow an object down, so if it is propelled in a direction, or a rotation, the object will resist that motion very little. This connects to angular velocity, which is how much the object will rotate over time, in other words, how fast it is turning. Angular acceleration is how much the angular velocity changes over time. This is particularly important when CubeSats get larger. The CubeSats are capable of docking together, but in order for two separate crafts to come together they must rotate the same way at the same velocity as they approach and connect and while they are connected. In other words, the CubeSats are seeking equilibrium when they dock, or a state wherein the net force in all directions is zero. The crafts do not want to be torquing or rotating. In space, they will still be moving, but if they are both moving in a straight line, the crafts can come together.
This can be difficult in space. There are many forces at work and some of those can cause deformities. After CubeSats go into space, scientists measure their elasticity, how much stress and strain the crafts have endured. It is important to know how much they have changed after experiencing the stress and extreme forces required to get out of Earth’s gravity and reach space. There are also questions about how the crafts’ propulsion fluids have done on the trip. As mentioned before, propulsion is crucial for positioning the CubeSats and getting accurate data from space. Fluid mechanics come into play in determining how the propulsion fluid will handle going to space and how it will operate in space. CubeSats can devote half of their space to the propulsion system. One type of propulsion system uses cold gas, which is basically a refrigerant similar to fire extinguisher fluid.
CubeSats also have to deal with what happens when they come back down. They can not stay in space forever and there are concerns about CubeSats, because they are easy and cheap to produce, filling up space with junk. However, CubeSats are meant to come back to Earth at some point and burn up in the atmosphere. They do this through gravity and an understanding of periodic motion. Gravity pulls downwards, creating potential energy. Potential energy is a gravitational constant. It is much stronger on Earth, but if the CubeSats orbit close enough or are propelled into the Earth’s gravitational hold, then gravity will pull them down. Scientists have to calculate the periodic, repeated motion of the Earth in its orbit to make sure CubeSats come down in the right place and at the right time.
Potential energy also could come into play during missions. Some applications of CubeSats have to do with Mars. Some CubeSats can watch other crafts land on Mars and monitor the potential energy working on the landing craft, when its parachute deployed and how much force it endured when landing on the planet. CubeSats can orbit Mars right above the landing craft to collect data as the other craft lands.
The potential uses for CubeSats are vast. They can orbit planets and the moon. They are low cost and can be deployed in greater numbers than traditional crafts in order to collect data throughout space. They can also help measure and explore the forces at play in space, including gravity, motion and force.