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From Vostok 1 to date, atmospheric reentry has been essentially passive. Passive here means that retrorockets are used to de-orbit, and then aerobraking is provided by the atmosphere. In contrast, active reentry would mean reentry under engine power (which may lie somewhere in the future perhaps).

As I understand it, this reduces the amount of fuel required to be carried for consumption only on the return journey. Indirectly, it allows more payload to be carried on the journey up — thus good math.

Are there any other advantages to a passive atmospheric reentry / aerobraking?

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    $\begingroup$ I would guess that a more passive system would also tend to be more reliable. The more actions that must be taken, the more opportunities for failure, and heat shields and even parachutes activated by explosives might be mechanically more simple (thus more reliable). Initially, such technology might also have been more mature/better understood (and so more reliable) and then gained the advantage of even greater understanding and familiarity for space use. Any design change involves risk, so being equally useful or even potentially better eventually may be insufficient reason for change. $\endgroup$
    – user56
    Commented Sep 20, 2013 at 12:32
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    $\begingroup$ Note aerobraking can be extremely efficient. The deceleration of reentry crafts is adjusted to prevent burn-up and lethal decelerations; it could be easily vastly higher. You'd need huge amounts of fuel to obtain as much efficiency from rocket engines (and as result absolutely gargantuan amounts for lift-off). While there may be little incentive outside the mass economy, the incentive of the mass economy is enormous; it's reducing the payload weight by some 95% - and so you'd need 20 times as much launch phase fuel! $\endgroup$
    – SF.
    Commented Nov 21, 2014 at 11:12

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Depending on what you mean by "passive," using the atmosphere to provide deceleration also provides larger cross range. This means you have either more landing sites to select from or less time in orbit required to line up with any given landing site.

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    $\begingroup$ Would it not be less options using only the atmosphere? $\endgroup$
    – Everyone
    Commented Sep 20, 2013 at 6:25
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    $\begingroup$ You will get more cross range from aero than propulsive control on a per pound basis. $\endgroup$
    – Erik
    Commented Sep 20, 2013 at 9:40
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    $\begingroup$ Cross range capability allows a vehicle to depart from its orbital ground track as it reenters. If you try to do this with propulsive control, you will burn a lot of fuel -- which you have to do if you are, say, landing on the moon. If you can react against an atmosphere with aerosurfaces, you don't need to carry that fuel. Of course, you need to carry the aerosurfaces if you want a large cross range. Even capsules however have some cross range as they are designed to have a lift vector that can be rotated by moving the center of gravity around internally. $\endgroup$
    – Erik
    Commented Sep 20, 2013 at 17:18
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    $\begingroup$ This is why the SpaceX Falcon 9R uses grid fins for its booster recovery: fuel savings! $\endgroup$
    – Jacob Krall
    Commented Feb 25, 2015 at 15:10
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    $\begingroup$ If you had no fuel limit, you can land wherever you like... $\endgroup$
    – drjpizzle
    Commented May 5, 2019 at 11:04
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The reliability of aero-dynamic drag is pretty good compared with propulsive alternatives. But if you had an unlimited fuel source and a reliable engine: in general you'd use it but discussing rockets without the scarcity of propellant is like the economy without scarcity of resources.

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