Could any existing armor, of the kind we put on tanks, ships,

>>32705596

>Houston this is Abrams M1A2 SEP descending from Angels 1000, guide me in, over

Absolutely not.

>>32705596

Steel melts at 2500 Fahrenheit, re-entry for the space shuttle got up to 3000. You need heat shielding.

Not without heat shielding

>>32705596
Read this and then you tell me homeskillet. Atmospheric reentry is no joke.

>>32705709
Top kek.

>>32705798
https://en.wikipedia.org/wiki/Atmospheric_entry#Thermal_protection_systems

Forgot muh link.

>>32705798
Read what?

All depends on how fast the reentry is and at what angle the object is entering. The heat generated by reentry is factored off speed and distance traveled through atmosphere.
All you need for a heat shield is insulation. The space shuttle was just aircraft aluminum underneath ceramic tiles that were held on with (no shit) RTV.

>>32705811
So if a spacecraft could somehow descend very slowly, could the heat become a non-issue?

>>32705831
I think so. It's the air resistance that causes the heat, if I remember correctly.

>>32705831
>>32705848
Of course they could. A human in a space suit could re-enter safely if they could manage their speed entirely. You don't burn up walking do you?

It's all based on friction. Incredible speed with a thickening atmosphere creates immense heat. It's what causes things to burn up.

>>32705596
Nope

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>>32705881
>You don't burn up walking do you?

Usually no, but sometimes yes.

>>32705881
Friction and compression heating are separate functions

>>32705596
Modern armor isn't designed to handle the heat of atmospheric re-entry, but if you had enough mass the armor could act like a heatsink. I think dropping a tank would get you a very large glob of metal at the end, but something like the Iowa might have thick enough armor to be recognizable after atmosphere entry at least.

>>32705831
http://www.vtaide.com/png/atmosphere.htm
>The thermosphere extends from 80 km above the Earth's surface to outer space. The temperature is hot and may be as high as thousands of degrees
I get that we're speculating but if you have the technology to decelerate in conditions like atmospheric re-entry then heat shielding would be a non-issue.

Sure.

A spaceship is a kind of ship.

>>32705596
If you made it about 10 yards thick, it'll survive no problem.

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>>32705881
Only sometimes.

>>32705969
He's saying as the air density increases there is more friction

>>32705596
>Could any existing armor
Yes, the kind we put on space ships works great.

>>32706017
Thermosphere is hot but at the same time it's so rarefied that the heat you lose through thermal radiation will outrun whatever it does to you.

A piece of paper could survive reentry.

Seriously.

The reason thing burn up on reentry is because they are coming out of orbit speeds or higher.

Things trying to enter the atmosphere going mach bazillion get hot as fuck.

A piece of paper entering atmosphere at 10mph isn't going to get hot at all.

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>>32705596

>>32705913
DAMN THAT GUY IS MOVING FAST

>>32705596
one way to find out

I suppose you could survive reentry in a non-shielded vessel by climbing up into a geosynch orbit, and then thrusting straight toward the Earth. The only question would be how fast you'd be booking by the time you entered the outer atmosphere due to gravity's increasing pull.

>>32707588
Why is the angle of descent gradual as compared to going straight first to the ground?

I understand that it is because you're cutting through air density in fractions rather than cutting straight through.

But what would the shielding have to be in order to survive something like that?

For this, let's assume it's the Endeavor.

>>32707588
That's not how orbits work. If you apply any thrust while in geostationary orbit you will no longer be in geostationary orbit. If you shrink the semi-major axis the orbital period shrinks. You don't gain anything from starting in GEO.

>>32707680
Point taken. Thanks.

>>32705811
>RTV
and Velcro.
Held one once

The angle of descent is gradual for a couple reasons.

The runway that a space shuttle lands on is long, and a space shuttle isn't capable of VTO/L, so it makes sense to preserve some amount of velocity phasing through the atmosphere than bullet diving in and having to course-correct from there. An important note is that diving straight down radially from geo-synchronous orbit doesn't result in a steady dive; you would still maintain the same angular velocity (you'd actually gain some energy from burning the thrusters to change vector) while decreasing radius, so this would be interpreted in a non-rotationary reference frame of the Earth as the object reentering breaking geosync and rotating around the Earth at an ever increasing rate as the radius decreases.

Secondly, it's important to remember that shuttles don't reenter traveling at the full 17,500 MPH. They tend to skip/bounce across the atmosphere for a while before reentry, using the atmosphere as a cushion to parasite some momentum before easing into the reentry. It would actually be exceedingly difficult to reenter at the angle they do at such a high velocity; the atmosphere would exert comparatively more normal force and could simply reject their reentry.

It's like skipping a rock across water; it bounces until it loses enough energy to dip under the surface.

>>32707808
Thanks.
Since you obviously know what you're talking about, why is there no such thing as high-altitude parachutes, streamers, etc? I've heard of aerobraking (like in movie 2010) and it seems the principle would translate...

>>32705773
So many layers of ERA? We will blast the atmospher away.

>>32705596
Sure, most ceramic armor would do just fine, assuming you layered it on thick enough.

Hell you could use just about anything if you used enough.

geometry is important as is your choice of descent, some ways are hotter than others. If you have enough fuel or big enough wings your reentry can be quite cool.

>>32708037

The upper atmosphere has such little air density that you'd need a massive parachute for it to provide enough drag, and if you had such a huge parachute the mass of the chute would have a parasitic relationship with the drag generation.

Parachute design has been consistently about refining the chute using lighter materials with stronger tensile strength. If you needed such a huge parachute to decelerate, even using lighter materials the entire system would be heavy and would put huge stresses on the parachute cables and the fibers themselves.

Basically, parachutes work well in air; if there isn't enough air, parachutes don't work well regardless of how big you make them. Make it big enough to cause deceleration in the upper atmosphere and the chute would break/tear in the lower atmosphere at the same speed.

>>32708378
>>32708037
its also the case that aerobraking in reality is *very* slow.

to use the Mars Global Surveyor as an example, it took more than 240 orbits, to go from a 45-hour orbital period, down to about a 2.5-hour orbit, over the course of 3 months, every single orbit, shaving off a few km/s of velocity, bringing it down from high orbit, to a low orbit.

you dont aerobrake in one single fiery pass like 2010 - its far less dramatic.