Traveling the huge ranges of space isn’t cheap for a spacecraft.

In these maneuvers, a spacecraft exchanges momentum in a close encounter with a planet to acquire or lower velocity, as required by the objective. To save expense and time or perhaps make up for absence of technological capabilities, gravity assists have been utilized in numerous interplanetary objectives to propel spacecraft towards their destinations. This includes using Jupiter’s gravity to slingshot the twin Voyager spacecraft out of the planetary system!

This post takes a look at some of the most outrageous and lesser spoke about gravity help maneuvers in past space missions. To get more acquainted with the ingenious method of gravity helps, read my explainer post with plenty of real mission examples.

Studying the Sun from above

In 1990, NASA and ESA introduced a joint mission called Ulysses to get the very first look at our Sun’s poles. For that, it would have to go out of the orbital plane of the planetary system, the aircraft in which planets go around the Sun.

Artist’s impression of the Ulysses spacecraft looking over at the Sun’s poles. Credit: NASA JPL

The only problem?

Much like how a close encounter with a world can alter a spacecraft’s speed, as when it comes to Voyagers, it can likewise modify the spacecraft’s inclination. In 1992, Ulysses passed closely over Jupiter’s north pole and the planet’s extreme gravity bent the spacecraft’s trajectory southward. This put Ulysses in a solar orbit that would take it past the Sun’s north and south poles at a disposition of 80 ° w.r.t the orbital airplane of the worlds.

Visual showing the orbital aircraft of the planets of the planetary system in orange. The Ulysses spacecraft accomplished a first-of-a-kind polar orbit around the Sun. Credit: tes teach

Keep In Mind that Ulysses didn’t literally “see” the Sun’s poles due to the fact that it didn’t have an optical cam but it had other instruments which took different clinical measurements.

Ulysses also offered us initially direct measurements of interstellar dust particles and of interstellar helium atoms in the solar system. The spacecraft also suddenly discovered itself in gaseous tails of comets every once in a while, accomplishing bonus science points.

The “Billion Euro gamble” of the comet chasing after probe

ESA’s Rosetta spacecraft– the very first to orbit a comet– thoroughly studied and kept an eye on the stylish two-lobed comet named 67 P.

Early activity of comet 67 P as imaged by the Rosetta spacecraft between January 31 to March 25,2015 Credit: ESA

Nevertheless, getting to comet 67 P in the very first location was an experience.

Rosetta’s 10- year journey through the planetary system included numerous flybys, including one around Mars. Credit: ESA

One of those gravity assists included a low-altitude Mars flyby in2007 It was a dangerous maneuver as the spacecraft passed by Mars by simply 250 km. Throughout the maneuver, Rosetta would be in Mars’ shadow, needing to count on the minimal battery supply instead of photovoltaic panels. The risk was that the batteries weren’t designed for the task The spacecraft was put in standby mode and interactions were switched off to save power.

Eventually, the Mars flyby proved successful and the spacecraft flew onward to its evasive target.

Image of Rosetta spacecraft above Mars as taken by the Philae lander video camera onboard Rosetta. Credit: ESA

Utilizing the Sun to sail

NASA’s MESSENGER spacecraft was the first ever to orbit Mercury. It was not without its difficulties.

Because Mercury lies relatively close to the Sun, any spacecraft on a direct trajectory to the planet will be accelerated by the Sun. MESSENGER would therefore reach Mercury with too expensive a velocity to achieve orbit without usage of excessive fuel, which is minimal onboard. The spacecraft can not use aerobraking either given that Mercury lacks a significant environment, like Venus or Earth have.

Gravity assists were once again a rescuer.

Trajectory of MESSENGER spacecraft from launch to orbit insertion around Mercury. Credit: APL

Flying too close could crash the spacecraft into a planet and flying too expensive would suggest excess use of fuel to attain the objective. Either way, getting off target might affect the objective in important ways.

The solution engineers developed was to utilize the Sun’s radiation pressure. Much like how wind can assist a boat browse, solar radiation can assist a spacecraft maneuver.

Solar radiation at Earth is not intense sufficient to apply enough pressure and move a spacecraft in a significant way. Mercury is much more detailed. Because radiation pressure increases by the inverse square law, it has to do with 7 times more effective at Mercury than Earth. This made solar cruising a practical alternative for MESSENGER.

When going by Mercury in all the flybys, engineers sent out commands to MESSENGER to align its solar panels in a way that the radiation pressure can slow the spacecraft down. By solar cruising at the right angles, the MESSENGER team removed usage of fuel in all the Mercury flybys without compromising precision. Reserved fuel also indicated increased mission life time and more of the great science at Mercury!

Artist’s impression of NASA’s MESSENGER spacecraft orbiting Mercury. Its photovoltaic panels were entitled for browsing utilizing solar radiation pressure. Credit: NASA

This was the first time a spacecraft had actually successfully used solar cruising as a propulsion-free trajectory control method for planetary flybys. For those thinking about the nerdy information, the MESSENGER team released a paper on the maneuvers.

MESSENGER image from the a Mercury flyby revealing lava-flooded craters and big areas of smooth volcanic plains on the planet. Credit: NASA

To finish up, space mission designers have actually utilized ingenious gravity assist maneuvers to see over the Sun, chase a comet and solar sail! While there are many more missions with insane trajectories, the ones highlighted here are a few of the less popular ones. Do you understand of more such intriguing orbital maneuvers? Comment below!

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