How to Keep a Spacecraft in Orbit

Over the past decade, low-cost satellites have proliferated into space at an ever-increasing rate, significantly lowering costs associated with studying Earth and developing ever more daring ideas for what these spacecraft can achieve.

Spacecraft are said to be in orbit when they are between perigee and apogee; their movement being controlled by electronic “eyes” that track the Sun and stars.

How do they get into orbit?

Scientists developed techniques for getting into space long before rockets existed; however, staying there can be more challenging than you’d imagine. Orbits provide “roadways in space” where satellites can travel safely for years without much assistance from Earth.

Rockets propel satellites into space, and once they reach a certain altitude, the satellite is released from its nose cone and set free. Still possessing momentum from its ride on the rocket, combined with gravity keeping its orbit intact.

But to maneuver a spacecraft in orbit, scientists rely on small engines known as reaction thrusters. These small thrusters fire out in different directions to alter the direction or altitude of their spacecraft; similar to how you may push against your tires or airplane wings to turn them, but with no air resistance present.

How do they stay in orbit?

Every day, more than 1,000 artificial satellites orbit Earth. These satellites enable digital communication worldwide and weather forecasting; TV/radio transmission; military operations; as well as scientific payloads that explore our planet and surrounding stars.

Satellites must maintain the velocity they initially achieved when launched from a rocket in order to stay in orbit. As gravity pulls them downward, their trajectory remains stable thanks to constant push back from rocket thrust.

As gravity pulls harder on satellites closer to Earth, their speeds increase accordingly. To avoid running into atmospheric traces that cause drag and potentially cause them to lose altitude and crash into Earth’s surface. Because of this fact, satellites such as Hubble Space Telescope and Global Positioning System satellites that orbit at lower altitudes must regularly use rocket engines to return back into their desired orbits.

How do they change their orbit?

Speed of a satellite depends on its distance from Earth and how strongly its gravitational pull has to be overcome, which explains why those nearer Earth require additional velocity to maintain their orbit, as well as additional fuel replenishments to keep going.

At higher altitudes, drag decreases significantly and spacecraft can remain in orbit for much longer. Unfortunately, however, they occasionally encounter Earth’s atmosphere which creates drag that causes its orbit to decay until eventually falling back down into it again.

Engineers using thrusters such as those found aboard the International Space Station use orbit phasing techniques to adjust a spacecraft’s orbit by adding or subtracting momentum by altering its inclination with respect to Earth’s rotational axis, known as orbit phasing. By altering momentum using such engines as these they can make substantial adjustments with relatively modest fuel costs.

How do they get back to Earth?

As soon as a spacecraft’s mission ends, its next task will be reentry to Earth. Re-entering our atmosphere can be challenging because its thick layers contain deadly atmosphere particles which could burn up your ship and astronauts inside it.

To prevent this from happening, astronauts use thrusters to tilt the spacecraft so that its bottom faces our atmosphere (roughly 40 degrees), so it travels nose first through hot ionized gases. This prevents radio communications with Earth for 12 minutes – an ionization blackout period.

3 minutes later, 2 drogue parachutes and 4 main parachutes are deployed to gradually slow the spacecraft from 350mph to around 15 mph before splashdown. When the spacecraft arrives back on Earth, its nose cone is removed for easy retrieval by recovery team members; astronauts then are flown back to a facility for medical checks and press interviews, similar to recent Axiom Space mission where former NASA astronaut Peggy Whitson joined Rayyanah Barnawi who made her inaugural spaceflight as paying customer.

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