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Robotic Spacecraft

My partner is Peter Nguyen

Robotic Vs. Unmanned Spacecraft (Put this subsection under design)

Robotic spacecrafts are specifically designed system for a specific hostile environment. Due to their specification for a particular environment, it varies greatly in complexity and capabilities. While an unmanned spacecraft is a spacecraft without personnel or crew and is operated by automatic (proceeds with an action without human intervention) or remote control (with human intervention). The term unmanned spacecraft does not apply that the spacecraft is robotic.

Spacecraft Propulsion

Spacecraft propulsion is a method that allows a spacecraft to travel through space by generating thrust to push it forward. However, there isn’t one universally used propulsion system: monopropellant, bipropellant, ion propulsion, and etc. Each propulsion system generates thrust in slightly different ways with each system having its own advantages and disadvantages. But, most spacecraft propulsion today is based on rocket engines. The general idea behind rocket engines is that when an oxidizer meets the fuel source, there is explosive release of energy and heat at high speeds, which propels the spacecraft forward. This happens due to one basic principle known as Newton’s Third Law. According to Newton, “to every action there is an equal and opposite reaction.” As the energy and heat is being released from the back of the spacecraft, gas particles are being pushed around to allow the spacecraft to propel forward. The main reason behind the usage of rocket engine today is because rockets are the most powerful form of propulsion there is.

Monopropellant Propulsion

For a propulsion system to work, there is usually always an oxidizer line and a fuel line. This way, the spacecraft propulsion is controlled. But in a monopropellant propulsion, there is no need for an oxidizer line and only requires the fuel line . This works due to the oxidizer being chemically bonded into the fuel molecule itself. But for the propulsion system to be controlled, the combustion of the fuel can only occur due to a presence of a catalyst. This is quite advantageous due to making the rocket engine lighter and cheaper, easy to control, and more reliable. But, the downfall is that the chemical is very dangerous to manufacture, store, and transport.

Bipropellant Propulsion

A bipropellant propulsion system is a rocket engine that uses a liquid propellent. This means both the oxidizer and fuel line are in liquid states. This system is unique because it requires no ignition system, the two liquids would spontaneously combust as soon as they come into contact with each other and produces the propulsion to push the ship forward. The main benefit for having this technology is because that these kinds of liquids have relatively high density, which allows the volume of the propellent tank to be small, therefore increasing space efficacy. The downside is the same as that of monopropellant propulsion system: very dangerous to manufacture, store, and transport.

Ion Propulsion

An ion propulsion system is a type of engine that generates thrust by the means of electron bombardment or the acceleration of ions . By shooting high-energy electrons to a propellant atom (neutrally charge), it removes electrons from the propellant atom and this results the propellant atom becoming a positively charged atom. The positively charged ions are guided   to pass through positively charged grids that contains thousands of precise aligned holes are running at high voltages. Then, the aligned positively charged ions accelerates through a negative charged accelerator grid that further increases the speed of the ions up to 90,000 mph. The momentum of these positively charged ions provides the thrust to propel the spacecraft forward. The advantage of having this kind of propulsion is that it is incredibly efficient in maintaining constant velocity, which is needed for deep-space travel. However, the amount of thrust produced is extremely low and that it needs a lot of electrical power to operate.

SpaceX’s Dragon

An example of a fully robotic spacecraft in the modern world would be SpaceX’s Dragon . The SpaceX Dragon is a robotic spacecraft designed to send not only cargo to Earth’s orbit, but also humans as well. The SpaceX Dragon’s total height is 7.2m (23.6ft) with a diameter of 3.7m (12ft). The total launch payload mass is 6,000kg (13,228 lbs) and a total return mass of 3,000kg (6,614 lbs), along with a total launch payload volume of 25m^3 (883 ft^3) and a total return payload volume of 11m^3 (388 ft^3). The total duration of the Dragon in Earth’s orbit is two years.

In 2012 the SpaceX Dragon made history by becoming the first commercial robotic spacecraft to deliver cargo to the International Space Station and to safely return cargo to Earth in the same trip. This feat that the Dragon made was only achieved previously by governments. Currently the Dragon is meant to transfer cargo because of its capability of returning significant amounts of cargo to Earth despite it originally being designed to carry humans.

Landing on Hazardous Terrain

In planetary exploration missions involving robotic spacecraft, there are three key parts in the processes of landing on the surface of the planet to ensure a safe and successful landing. This process includes a entry into the planetary gravity field and atmosphere, a descent through that atmosphere towards a intended/targeted region of scientific value, and a safe landing that guarantees the integrity of the instrumentation on the craft is preserved. While the robotic spacecraft is going through those parts, it must also be capable of estimating its position compared to the surface in order to ensure reliable control of itself and its ability to maneuver well. The robotic spacecraft must also efficiently perform hazard assessment and trajectory adjustments in real time to avoid hazards. To achieve this, the robotic spacecraft requires accurate knowledge of where the spacecraft is located relative to the surface (localization), what may pose as hazards from the terrain (hazard assessment), and where the spacecraft should presently be headed (hazard avoidance). Without the capability for operations for localization, hazard assessment, and avoidance, the robotic  spacecraft becomes unsafe and can easily enter dangerous situations such as surface collisions, undesirable fuel consumption levels, and/or unsafe maneuvers.

Integrated Sensing for Entry, Descent, and Landing of a Robotic Spacecraft

The way Integrated Sensing works is that it incorporates an image transformation algorithm to interpret the immediate imagery land data, perform a real-time detection and avoidance of terrain hazards that may impede safe landing, and increase the accuracy of landing at a desired site of interest using landmark localization techniques. Integrated Sensing completes these tasks by relying on pre-recorded information and cameras to understand its location and determine its position and whether it is correct or needs to make any corrections (localization). The cameras are also used to detect any possible hazards whether it is increased fuel consumption or it is a physical hazard such as a poor landing spot in a crater or cliff side that would make landing very not ideal (hazard assessment).