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In this question, I asked whether it would be possible to make a reentry vehicle that could slow down from orbit and glide to the ground entirely passively. The answers and comments point out several reasons why it is probably impossible for a plane-sized object.

However, there still seems ways to decrease the heating of a reentry vehicle compared to existing designs. For example, the VentureStar project was supposed to use metallic tiles instead of the much more heat-resistant tiles of the Space Shuttle.

What would be the minimal heating a realistic reentry vehicle could hope to achieve?

The vehicle should at least mass a few tons, as the square-cube law seems to make it easier for smaller ones. Other considerations like extravagant reentry duration, awkward shape or limited landing sites can be ignored.

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    $\begingroup$ What metric are you looking for with heating? Temperature, energy, power, etc. Also what region are you interested in. With ablatives, you have a huge amount of heating in some parts (the parts that are ablating), and very little heating in others. $\endgroup$ – Cort Ammon Jul 16 '19 at 0:51
  • $\begingroup$ @CortAmmon Temperature is probably the best metric. The idea is, what would allow to have the lightest and/or cheapest non-ablative, ideally reusable tiles. Maybe there are other important metrics for this? So let's say what would make easiest the job of the engineers tasked with reentry thermal protection. $\endgroup$ – Eth Jul 16 '19 at 8:31
  • $\begingroup$ You could come to complete stop in orbit just above the atmosphere, then slowly fall to Earth using retro rockets (provided you have the fuel to do so). The only way you're going to lose base atmospheric friction is if you decrease the orbital speed without increasing the rate of descent too much. If you reboost vertically to counter-act 9.8m/s gravity (for X seconds) while inside the atmosphere you could potentially lose all horizontal velocity over time slowly. How slow? As slow as you want, provided you have the ability to point the craft outward. Is it practical/feasible? No probably not. $\endgroup$ – Magic Octopus Urn Jul 18 '19 at 18:58

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