# Why not bring a rocket to idle velocity for less violent and safer re-entry? [duplicate]

Since kinetic energy have to be converted into heat during re-entry, the re-entry into the earth's atmosphere seems very violent.

Why most rockets or crew re-entry modules plunge into the earth's atmosphere at it's full orbital velocity, leaving at the mercy of the heat tiles? Why don't they come to idle velocity before re-entry? Will carrying more fuel for the re-entry burn more safer and easier than the heat insulation mechanism?

• An ablative heatshield is much simpler and thus more reliable than a rocket engine. No need to rely on heat tiles and their special problems. – Uwe Sep 9 '20 at 11:45
• The amount of fuel to slow down the reentry vehicle is exactly the same amount to accelerate it, meaning you need a full size rocket. However you need another rocket to bring this one to orbit as well. As a result the cost is rocket equation squired. – user3528438 Sep 9 '20 at 12:15
• – uhoh Sep 9 '20 at 12:15
• @uhoh I like that one very much; it just seemed like less of an exact duplicate. – Organic Marble Sep 9 '20 at 12:43

This exponential increase is the central problem of rocketry: The fuel required to increase your speed by one km/s multiplies your weight by about 1.4. To get into orbit, you need to increase your speed to 8 km/s, which means you'll need a lot of fuel: $$1.4\times1.4\times1.4\times1.4\times1.4\times1.4\times1.4\times1.4\approx 15$$ times the original weight of your ship.