JPL launches spacecraft into orbit via launch vehicles like Soyuz or NASA’s shuttles; each one designed for specific tasks.
They must generate enough thrust to counter the force of gravity pulling down on them, but to do that they require lots of fuel.
How a Spacecraft is Launched
Spacecraft may be efficient machines, but their launch requires significant amounts of fuel. An imbalanced force propels spacecraft upward due to pressure differences between their front end (closed) and their back end (open).
Burning gases within the engine causes it to push upward, pushing spacecraft-launch vehicle assemblies up through the upper atmosphere. For this process to work efficiently, rocket engines must accelerate rapidly.
At the launch site, both spacecraft and launch vehicle undergo ATLO (Assembly, Testing and Launch Operations). Assembly begins in a large clean room while engineering components arrive as scheduled; eventually the spacecraft is attached to its launch vehicle adapter and enclosed in a fairing for protection; propellant is loaded; any necessary pyrotechnic devices activated – all taking place approximately three months before launch day.
The Launch Vehicle
Launch vehicles must transport spacecraft into orbit from Earth using all necessary fuel and systems, such as rocket engines.
Rockets generate thrust by burning explosive chemicals and emitting exhaust fumes. In order to achieve thrust, rockets must accelerate very rapidly before resisting gravity’s pull as well as friction from Earth’s atmosphere during their flight into space.
Engineers carefully consider how to integrate a spacecraft into a launch vehicle for optimal operation. They make sure it will fit inside, and verify its trajectory so it reaches its target destination safely and on schedule.
Many spacecraft stay within low Earth orbit (LEO), but those traveling farther require extra assistance in reaching escape velocity to escape Earth’s gravity and move towards interstellar travel. Such missions call for powerful rockets like America’s Space Shuttle or Evolved Expendable Launch Vehicle (EELV).
The Payload
Payloads come in various shapes and sizes, from scientific instruments on satellites to the crew members of spacecraft. All must withstand the intense forces experienced during launch; accelerations that reach several G’s occur within mere seconds.
Before being loaded onto the rocket, payloads must be tested for their ability to withstand conditions in space. Both vehicle and payload are then put through an intensive Terminal Countdown Demonstration Test that simulates real launching conditions up until when rocket engines would ignite to begin their mission into space.
This simulated launch evaluates how well spacecraft and payload are attached to and communicating with their rocket, as well as their ability to endure extreme vibrations, buffeting, oscillations and oscillations during launch. Finally, propellants and explosive devices to separate its stages or destroy spacecraft if it veers off course are loaded on.
The Orbit
Once in orbit, a spacecraft follows an orbital trajectory similar to that of an upwardly launched stone; momentum from its rocket keeps it orbital while gravity keeps it there. This constant tug between momentum (energy from the rocket) and gravity ensures it remains in this trajectory.
Orbits can either move prograde (in the direction of planet rotation) or retrograde (moving oppositely to planet rotation). But those aren’t your only options – various orbital configurations exist to enable everything from joyrides for space tourists to giant constellations of satellites beaming high-speed internet down to Earth.
All this hinges on a carefully timed launch window, known as a “launch window.” A spacecraft bound for rendezvous must be launched at precisely the right moment so as to overlap orbits; this requires applying equations of motion to range and Doppler data from observatories worldwide.