NASA’s Parker Solar Probe has broken speed records over the last several years by continuously approaching closer and faster towards the Sun, picking up speed with each pass.
But, what exactly is spacecraft speed, and how are scientists measuring it? In order to answer this question, let’s first determine what we mean by “speed.” To do so, let’s discuss both average and instantaneous speeds.
How do we measure it?
Spacecraft speed can be measured by dividing its total distance traveled by total time taken – this yields its average speed while instantaneous speed allows us to better pinpoint its measurements at any given moment.
Spacecraft that are meant to escape Earth’s gravitational pull and travel towards other planets must move at high speeds in order to do so. Achieving 0.25c, which would be manmade objects’ fastest possible speed, is no easy feat; this requires vast quantities of rocket fuel as well as engineering designs capable of withstanding impact from cosmic debris at such speeds.
One method we can use to measure spacecraft acceleration is through frequency shift in their communication signal received on Earth. This gives scientists a precise value of its distance; combined with information about direction, this provides its speed. This method works even over long distances that cannot be measured with radar.
How do we change it?
Space travel presents unique challenges. Without air or water acting against it, spacecraft are able to quickly change speed and direction by extruding mass in one direction and experiencing an opposing reaction force (Newton’s Third Law). This is how rockets create thrust.
As gravity can only take you so far, escaping Earth and reaching outer space requires breaking free from its gravitational pull and accelerating at light speed – something the human body simply isn’t equipped to manage.
To make spaceflight possible, scientists are developing new types of propulsion. One possibility being considered involves controlled nuclear fusion – the process by which atomic nuclei are combined together in order to generate energy – although this technology could take up to 10 years before becoming viable for space travel.
What is the most common trajectory for a spacecraft?
Vertical launches typically result in spacecraft falling back towards Earth (unless they reach speeds sufficient to escape its gravitational influence), but for planetary-exploration missions spacecraft must typically enter an orbit around their target planet that balances with Earth’s gravitational pull at that altitude. In order to do this, for curved orbit missions spacecraft must attain speeds such that their centrifugal acceleration exactly equals Earth’s gravitational force at that altitude.
Trajectories required to achieve this are determined through Doppler velocity measurements on long radio-based tracking arcs, complete with precision transmitters and receivers located at deep space antenna complexes, as well as range measurements to estimate distance traveled. This allows the spacecraft’s computer to compare its actual flight path against that planned at any given moment.
Spacecraft trajectory modifications typically include changing attitude (by rotating around various axes or firing thrust motors) or firing thrust motors, respectively. For more precise trajectories, however, three onboard gyroscopes can measure very subtle velocity changes to provide necessary data to a navigation computer.
What is the fastest man-made object to reach another world?
If you had access to a spaceship capable of travelling at the speed of light, traveling between worlds would take just 49 seconds – faster than even Saturn V rocket which took astronauts to the Moon or SpaceX starship which will bring us Mars! But these are both rockets; not probes.
NASA’s uncrewed Parker Solar Probe recently set the fastest human-made object ever to reach another planet, recording speeds of 394.736 miles or 635,266 kilometers an hour as it zoomed closer and closer to the Sun. This record eclipsed one set by itself back in 2021 against Voyager 1.
Helios reached speeds of 157,000 mph as it crossed our solar system, while Parker has still far to go before reaching those speedy cosmic giants that we only dream about.