Making it into space. How have we explored space so far? What are we doing right now? What does the future of space travel look like?
Escape velocity
To make it into space, you first need to escape the gravity that keeps us on the ground.
During launch, spacecrafts take rocket-powered flights that reach extremely high speeds. They need to fly through the atmosphere and reach orbital velocity. Orbital velocity is the speed at which a spacecraft goes into orbit. If nothing else was pulling on it, the craft moving at a steady speed would move off in a straight line into space. But gravity will pull the craft back towards the mass of the Earth.
At orbital velocity, the motion outward and the pull back toward the Earth balance out, and the craft will go into orbit around the Earth.
Escape velocity is the speed at which the craft escapes the gravity of the Earth, if there is no extra energy being applied. If a rocket continues providing energy to its spacecraft, it is possible to escape Earth’s gravity without ever reaching escape velocity.
To do this, the rocket would need to continue to accelerate, providing extra bursts of energy for the spacecraft.
The only way we’ve reached the high speeds needed for launch so far is by burning huge quantities of chemical fuel. Usually, a combination of solid and liquid fuels is used.
Manned vs. unmanned
Sending people into space is very expensive, difficult, and tough for the astronauts involved. Increasingly, astronomers are turning to unmanned spacecraft. Robotic probes can be controlled remotely to gather data.
Unmanned space probes are generally cheaper to run. Without the need to keep humans safe, fed, and comfortable in space, it becomes much simpler to build a spacecraft. Moreover, robots can travel to places with conditions far too extreme for humans – for example, missions passing close enough to the sun that the radiation and heat would kill a human.
There are advantages to human space travel, too, though. The flexibility of human intelligence can’t be matched by robots quite yet. Humans can react to the unexpected – and quickly. When Skylab was launched in 1973, it sustained damage to a heat shield and solar panel. The human crew was able to repair this damage and keep the mission on track. Although robotic probes can be controlled from the ground, messages take time to reach them because of the distance. An instantaneous reaction is impossible.
By using both, astronomers can benefit from the strengths of manned and unmanned space missions.
The race to space: astronomical firsts
Space travel was changed forever by the politics of the Cold War and the space race between the United States and the Soviet Union.
In 1957, the first man-made object was launched into orbit by the Soviets – Sputnik. In response, the USA created the National Aeronautics and Space Administration (NASA) in 1958. In 1959, the soviets launched Luna 2 – the first space probe to hit the moon and in 1961, Yuri Gagarin became the first man to orbit the Earth.
The frenzied race continued, and the firsts continued to pile up. Between 1961 and 1964, NASA’s budget increased by 500%. The race incurred its casualties – 3 astronauts were tragically killed in 1967 when a launch simulation went wrong.
The space race reached its climax in 1969, when the Apollo 11 mission landed on the moon.
It’s unlikely we’ll see such an explosive surge forward in space travel again – from the first satellite to men on the moon in just over a decade. But with the space race, we took a giant leap into the universe.
Cassini
Cassini was a robotic space probe sent to investigate Saturn and its moons. The result of a collaboration between NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI), it spent nearly 20 years gathering data in space.
It also carried a passenger: the Huygens probe.
This probe was released and parachuted down to Titan, Saturn’s biggest moon, in 2005. This remains the furthest landing from Earth ever made.
The Cassini mission gave us valuable insights into Saturn and its moons. Enceladus, an icy moon of Saturn, has oceans of salty liquid water hiding under its surface. Jets from these oceans spray into space, and Cassini was able to directly sample one of these plumes. This sample revealed a cocktail of organic materials, water vapor, carbon dioxide, carbon monoxide, and volatile gases.
At the end of the mission, Cassini crashed into Saturn in a ‘grand finale’. During its final dive, it sent data back to Earth for as long as it could. It burned up in Saturn’s atmosphere shortly after it stopped transmitting data.
International Space Station
The International Space Station (ISS) is the result of truly global cooperation. 5 space agencies are involved: NASA, ESA, the Japan Aerospace Exploration Agency (JAXA), the Canadian Space Agency (CSA), and Russia’s space agency (Roscosmos).
At 356 feet (109 meters), the ISS is huge. It’s only 1 foot shorter than an American football pitch. It’s the biggest space station in low Earth orbit and has been continuously occupied for over 20 years, since 2000.
It’s used as a space research laboratory, where experiments can take place under microgravity and in the environment of space.
A huge range of fields are represented in the experiments carried out aboard the ISS – from materials science to space medicine. For example, the Alpha Magnetic Spectrometer-02 docked on the ISS looks for evidence that could help us identify dark matter and better understand the formation of the universe.
The ISS has faced some criticism from the scientific community, who question whether it’s worth the huge expenses involved. With increasing geo-political tensions on the ground, questions also hang over the future of this cooperative effort in space.
Mars rovers
Mars rovers are robotic vehicles designed to explore the planet’s surface. There have been 6 successful Mars rovers so far, all but one of which have been NASA missions.
The first successful Mars landing was Sojourner, launched in 1996 and designed to demonstrate that scientific equipment could be sent to Mars at a relatively low cost. It operated for 90 days.
Opportunity and Spirit were both launched in 2003. Evidence from both suggested that there used to be water on Mars – possibly enough to sustain life. Spirit operated for 6 years and Opportunity for 15 years, far longer than either was planned to last.
Curiosity, Perseverance, and Zhurong are all currently active on Mars. Curiosity was launched in 2011, and Perseverance was launched in 2020: both are investigating whether Mars could have supported life in the past.
Zhurong, launched in 2020 by the Chinese National Space Administration, is collecting more general environmental data, including information on the magnetic field of the planet.
Hayabusa
Hayabusa was a robotic spacecraft developed by JAXA and launched in 2003. It traveled to the 25143 Itokawa Near-Earth asteroid, where it retrieved samples of materials to return to Earth.
Hayabusa was the first spacecraft designed to land on an asteroid and take off again afterward. Originally, the plan was to briefly touch the asteroid, but it ended up lingering for around 30 minutes instead.
The mission delivered the first sample from an asteroid that we’d ever seen on Earth, in a capsule that landed in Australia. Before this, we had samples of meteorites – chunks of rock that have landed on Earth from space – but it’s hard to match up these meteorites with known asteroids, so this direct sample from a well-characterized asteroid was significant.
JAXA also used Hayabusa to test new technologies, including Ion engines for flying in space.
Commercial space travel
Government-funded organizations have largely driven the history of space travel. Space travel has become synonymous with organizations such as NASA. But private companies such as SpaceX are starting to make an impact. Already, SpaceX works with NASA to fly people to the ISS.
The space economy uses equipment in space for commercial gain. Space-for-earth activities dominate – using technology in space for goods and services on Earth. Familiar examples include satellite navigation and satellite TV. Telstar 1 was one of the pioneers of the space economy. Launched by NASA, it was the first privately sponsored satellite.
Funding came from AT&T and Bell Telephone Laboratories, and Telstar was used in the first live TV broadcast between the USA and Europe. By comparison to space-for-earth, the space-for-space economy is tiny.
But this economy – concerning goods and services made in space for use in space – is likely to grow. Companies like Made in Space, Inc. are leading the way in the space-for-space economy. After 3D printing a wrench on the ISS in 2014, they now hold a contract to create metal beams in space for NASA.
Space tourism
Before 2000, a journey into space was the preserve of astronauts. Increasingly, traveling to space is also available to the extremely rich.
Recreational space flights are known as space tourism. Several companies have invested in space tourism programs, including SpaceX, Blue Origin, and Virgin Galactic.
Virgin Galactic and Blue Origin both launched suborbital flights in 2021, with Blue Origin aiming to take longer orbital flights in the future. SpaceX plans to focus on longer flights and launched the first orbital flight crewed by tourists in 2021.
There are even plans for a hotel in space. Orbital Assembly Corporation is aiming to open the luxury Voyager Station by 2027.
The draw of experiencing microgravity or the ‘overview effect’ – the shift in perspective caused by seeing the Earth from space – means these companies have long waiting lists. But for the foreseeable future, a holiday on the moon will remain a dream for most people.
