Uncrewed spacecraft

Uncrewed Spacecraft: The Future of Exploration

Imagine a world where humans venture into space without the need to bring along all the necessities that come with life support systems—uncrewed spacecraft are the key to this future. These vehicles, often referred to as robotic spacecraft, are designed to explore regions too dangerous or inhospitable for human habitation.

But what exactly is an uncrewed spacecraft? It’s a vehicle without people on board and can operate with varying levels of autonomy from human input. They’re used because they offer lower cost and risk factors compared to crewed missions, making them ideal for exploring hostile environments like Venus or the vicinity of Jupiter.

Now, let’s dive into why uncrewed spacecraft are so crucial. One major advantage is their ability to be sterilized, a process that ensures they don’t carry Earth micro-organisms that could contaminate other planets. In contrast, humans cannot be sterilized in the same way, making them potential carriers of contamination.

History of Uncrewed Spacecraft

The First Steps into Space

Our journey with uncrewed spacecraft began on October 4, 1957, when the Soviet Union launched Sputnik 1. This was not just a technological marvel but also marked the beginning of the space age. Nearly all satellites, landers, and rovers are robotic spacecraft, making them indispensable tools for exploration.

While the first uncrewed space mission was Sputnik, the first robotic spacecraft was launched by the Soviet Union on July 22, 1951. This was followed by the launch of Sputnik 1 and Sputnik 2 in 1957, which were both significant milestones in space exploration.

The United States also made its mark with Explorer 1, launched on January 31, 1958. This satellite carried sensors that confirmed the existence of the Van Allen belts, a major scientific discovery at the time. The US continued to explore the moon and beyond, launching Vanguard 1 in March 1958, which remains in orbit as of 2016.

The first attempt to land on the Moon was Luna E-1 No. 1 by the Soviet Union in September 1958. It wasn’t until January 4, 1959, that Luna 1 successfully orbited around the Moon and then the Sun. The US followed suit with Mariner 2, which studied Venus and revealed its extremely hot temperature in 1962.

The first interstellar probe was Voyager 1, launched on September 5, 1977. It entered interstellar space on August 25, 2012, followed by its twin Voyager 2 on November 5, 2018. These probes have revolutionized our understanding of the solar system and beyond.

Other countries like France, Japan, China, the United Kingdom, India, Israel, Iran, North Korea, and South Korea have also successfully launched satellites using their own launch vehicles, marking significant advancements in space technology.

Designing Uncrewed Spacecraft

In spacecraft design, the US Air Force considers a vehicle to consist of the mission payload and the bus (or platform). The bus provides physical structure, thermal control, electrical power, attitude control, and telemetry, tracking, and commanding. This complex system ensures that the spacecraft can function autonomously in space.

The flight system is divided into subsystems including:

• Structure: Provides overall mechanical integrity of the spacecraft.
• Data Handling: Stores command sequences, maintains the spacecraft clock, collects and reports spacecraft telemetry data, and collects and reports mission data.
• Attitude Determination and Control: Maintains the correct spacecraft orientation in space despite external disturbances.
• Entry, Descent, and Landing: Integrates sensing for immediate imagery land data, detection of terrain hazards, and landmark localization techniques. This is crucial for landing on hazardous terrain where the robotic spacecraft must estimate its position compared to the surface, perform hazard assessment, and adjust its trajectory in real time.

Without these capabilities, the robotic spacecraft becomes unsafe and can easily enter dangerous situations such as surface collisions, undesirable fuel consumption levels, and/or unsafe maneuvers. This is why careful design and testing are essential for successful missions.

Landing on Hazardous Terrain

Landing on hazardous terrain involves an entry into planetary gravity fields and atmospheres, a descent through those atmospheres towards intended regions of scientific value, and a safe landing. The robotic spacecraft must estimate its position compared to the surface, perform hazard assessment, and adjust its trajectory in real time to avoid hazards.

This is no small feat; it requires advanced technology and precise calculations. For example, the Mars rovers use sophisticated algorithms to navigate rocky terrain and avoid obstacles. Without this capability, landing on hazardous terrain would be extremely risky and potentially disastrous for the mission.

Telecommunications Subsystem

The telecommunications subsystem is crucial for communication between the spacecraft and ground stations on Earth or other spacecraft. It includes radio antennas, transmitters and receivers used to send data back to Earth while uncrewed spacecraft can be robotic or non-robotic. This ensures that mission data and images are transmitted back to scientists and researchers.

Power Supply

The supply of electric power on spacecraft generally comes from photovoltaic (solar) cells or a radioisotope thermoelectric generator. Other components include batteries for storing power and distribution circuitry that connects components to the power sources. This ensures that the spacecraft has a reliable source of energy throughout its mission.

Protection Against Extreme Conditions

Spacecraft are often protected from temperature fluctuations with insulation, and may use mirrors and sunshades for additional protection from solar heating. They also need shielding from micrometeoroids and orbital debris to ensure their safety in the harsh environment of space.

Propulsion Systems

Spacecraft propulsion is a method that allows a spacecraft to travel through space by generating thrust to push it forward. Propulsion systems include monopropellant, bipropellant, and ion propulsion. Monopropellant propulsion uses a single fuel line with an oxidizer chemically bonded into the fuel molecule. Bipropellant propulsion uses two liquid propellants that spontaneously combust when in contact with each other. Ion propulsion generates thrust by electron bombardment or accelerating ions.

By shooting high-energy electrons at a propellant atom, it removes electrons and results in a positively charged ion being accelerated through grids to achieve 40 km/s speed, providing constant velocity for deep-space travel. Mechanical devices are controlled by motors or pyrotechnic devices. Robotic spacecraft use telemetry to send data back to Earth while uncrewed spacecraft can be robotic or non-robotic.

Space Probes and Telescopes

Space probes explore outer space with different instruments and gather materials from targets, using various orbits and trajectories such as Hohmann transfer or gravitational slingshots. Space telescopes avoid electromagnetic radiation distortion, light pollution, and observe different types of objects. They are divided into two types: satellite surveys and targeted observations.

Cargo Spacecraft

Cargo spacecraft transport supplies to space stations, including food, propellant, and equipment. Automated cargo spacecraft have serviced space stations since 1978. Currently, the ISS relies on Progress, Cargo Dragon, Cygnus, Tianzhou, American Dream Chaser, HTV-X, and European Automated Transfer Vehicle for resupply missions.

Uncrewed spacecraft are not just tools; they are the future of exploration. They have opened up new frontiers in space and continue to push the boundaries of what we can achieve. As technology advances, so too will our ability to explore the cosmos with greater precision and efficiency.