When you put your hand out the window of a be active car , you palpate aforce agitate against you called retarding force . This force opposes a moving vehicle , and it ’s part of the reason why your car of course slows to a full point if you take your foot off the gas foot lever . But drag does n’t just slow down auto .
Aerospace engineer are working on using the pull force out in space to develop more fuel - efficient spacecraft and missions , deorbit spacecraft without creating as muchspace rubble , and even placeprobes in area around other planets .
Space is not a complete vacuum — at least not all of it . Earth ’s atmospheregets thin with height , but it has enough tune to impart a force out of retarding force on orbit spacecraft , even up to about620 miles(1,000 kilometers ) .
NASA’s Mars Reconnaissance Orbiter used aerobraking to orbit around Mars.© JPL/NASA
As anaerospace engineering professor , I learn how drag affects the motion of space vehicle in eye socket . Aerobraking , as the name suggest , is a type of maneuver that uses the thin melodic phrase in space to utilise a drag force out in the focal point opposite to a spacecraft ’s move , much like braking in a railway car .
Changing an orbit
In space , aerobraking can change the field of a space vehicle while downplay the use of its propulsion system and fuel . Spacecraft that area around Earth do so intwo types of orbits : circular and elliptical . In acircular orbit , the space vehicle is always at the same distance from the center of the Earth . As a upshot , it ’s always moving at the same speed . An prolate compass is stretched , so the distance from Earth− and the speed the craft moves at− changes as the ballistic capsule travels along the orbit .
The closest distributor point in an elliptical orbit around Earth , where the satellite or space vehicle is go quickest , is calledthe perigee . The farthest distributor point , where it ’s moving slowest , is calledthe apogee .
The general idea behind aerobraking is to start in a large orbitual ambit and maneuver the spacecraft into a extremely elliptical orbit , so that the lowest distributor point in the orbit− the perigree− lies in the denser part of the upper atmosphere . For Earth , that ’s between about 62 and 310 miles ( 100 and 500 km ) , with the option depending on meter required to complete the area change .
Aerobraking brings a spacecraft from a large, circular orbit into a highly elliptical orbit, into a smaller, more circular one.
As the spacecraft passes through this lowest point , the atmosphere exerts a drag force on it , which reduces the stint of the orbit over fourth dimension . This force play rip the craft toward a circular sphere modest than the original orbit .
The first evasive action to put the spacecraft in an elliptical orbit so that drag can take gist does require using a propulsion system and some fuel . But once it ’s in the elliptical orbital cavity , drag in from the standard atmosphere slows the workmanship , and it does n’t need to use much , if any , fuel .
Aerobraking bring a craft from a large orbit to a small area and is not reversible− it ca n’t increase the size of it of an orbit . increase the size of an orbit or raising the spacecraft to a in high spirits orbit requires propulsion and fuel .
While an elliptical orbit is closed, a hyperbolic orbit doesn’t go all the way around a planet.
Aerobraking uses
A common pillowcase where spacecraft controllers use aerobraking is when change the craft ’s orbit froma geostationary orbit− GEO− to alow Earth orbit , LEO . A GEO orbit is a circular reach with an ALT of roughly 22,236 stat mi ( 35,786 km ) . In GEO , the spacecraft crap one orbit around Earth in 24 hour , so the spacecraft always stays above the same point on Earth ’s surface .
Before aerobraking , the spacecraft ’s onboard actuation system thrusts in the opposite guidance of the GEO orbit ’s motion . This poke puts it into an egg-shaped orbit . The trade slide by through the atmosphere multiple metre , which finally circularizes the field .
Once it makes it to LEO , the space vehicle may involve to use a little bit of fuel to propel itself up into its objective orbit . Usually , the low-down breaker point of the original prolate orbit is low than the last objective rotary orbit .
This process is conceptually similar to how theU.S. Space Force ’s X-37B used aerobraking in early 2025 . The U.S. Space Force describe that itsunmanned spaceplane , X-37B , used aerobraking . This psychometric test demonstrated the trade ’s agility and maneuverability .
Another software for aerobraking is to make a spacecraft deorbit− or reenter the atmosphere− after it has stopped working . This way , the caller or agency can throw away of the spacecraft and avoidcreating quad junk , since it will combust up in the lower atmosphere .
Aerobraking for interplanetary missions
A few Mars mission , including theMars reconnaissance orbiterand theMars Odyssey orbiter , have used aerobraking to get to their target eye socket around the red satellite .
For interplanetary commission like these , scientists expend aerobraking in conjunction with the craft ’s onboard propulsion system . When a spacecraft get in at Mars , it does so in ahyperbolic field .
Unlike a circular or an elliptical reach , the spacecraft ’s way of life in inflated orbit wo n’t keep it orbiting around Mars . Instead , it would wing through and depart Mars− unless it use thrust from its propulsion system to get “ fascinate ” into a closed ovate orbit .
As the space vehicle arrives at Mars , the onboard actuation system fires to provide the force necessary to enamor the ballistic capsule into a extremely elliptical orbit around Mars . Once captured , scientists use aerobraking over several orbital passes through the atmosphere to achieve the final range , in general a circular one .
Aerobraking simulated military operation can leave in significant fuel delivery . As man get closer tolanding on the control surface of the red major planet , the fuel savings enabled by aerobraking could save mass and reserve each ballistic capsule channelise to Mars to take more supplies .
In the grand electric discharge of infinite exploration , aerobraking is not just a maneuver . It has a essential role to play in the future tense of quad operation and planetal missions and settlement .
Piyush Mehta , Associate Professor of Space Systems , West Virginia University . This clause is republished fromThe Conversationunder a Creative Commons license . learn theoriginal article .
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