Do Spacecraft Really Have To Endure The Hazards of Reentry

There’s one solution you’ve missed: Using the mega maid to remove earth’s atmosphere entirely, thus solving the problem of reentry!

You make watching YouTube more efficient by presenting two videos at the same time.

Is reentry really necessary? If I went to space, I would insist on coming back, so yes, it's necessary.

That reentry video always gives me a strong sense of relief and appreciation for the safe embrace of earth. Even compared to ending up alone in the middle of the ocean, which is normally considered an exceedingly horrible and deadly situation, it's a warm, protective and comfortable bosom compared to space's sheer hostility to life.

That reentry footage was terrific.

There was one professor in the early days of Apollo that explained you could use rockets to overcome gravity to slowly deorbit but the amount of fuel was more than what it took to get to orbit. So, a heat shield was more efficient, less cost, less massive. His sketches showed multiple rockets pointing towards earth center and rockets slowing the spacecraft down to match earth’s rotation, then allowing the ship to slowly descend! Fuel requirement was enormous.

Although I had seen it before, I appreciate you leaving the re-entry video up as you narrated. The vortex of superheated gases behind the capsule is mesmerizing.

Scott, this episode was fantastic. I loved that you ran the video through your whole segment. It was a great idea and worked well. Bravo 👌

I feel like I'm in a capsule returning from the Moon and Scott Manley is on the intercom just rambling on and on about re-entry physics while I'm trying to enjoy this moment.

I want more of these refutations of common "Why dont they just do X" I love your content Scott, followed you since the early days of KSP, I remember being hyped every single time you released a "100% reusable space program" video because your solutions to things were so creative.

I love using the ballute mod in ksp. Shoot for a periopsis of around 56 Km, and deploy the ballute as soon as I'm in the atmosphere. It's so much more gentle landing.

Fantastic footage and an excellent explanation for what’s going on. Thank you, Scott A bit of trivia about the L/D ratio for airliners: the B767 has 12 (they discovered it during the Gimli glider incident, go check it out), while the Airbus flock tend to have around 15 (yes, even that monstrosity known as the A380). The B747 and 777 also have around 15, while the original B737 was supposed to have 17 (highly doubt that, but hey). The B787 and B777X are at 20! Except the B767’s, which was actually found out by accident, the rest are all theoretical, so I wouldn’t count on them if were to have a total loss of power on all engines anywhere far from an airport safety cone. Gliders are on another planet. The first plastic gliders of the 1960s had around 32-35 at relatively low speeds, while more modern ones like the Nimbus 4 have a manufactured-declared L/D of 60+. Recently manufacturers have stopped publishing the “polar curve” of the gliders they make, so we don’t exactly know their design performance with the seams level of detail, but I’d guess is not very far from 50 to 55. The major improvement on previous iterations lies in the speed at which they obtain those L/D ratios, given by the much higher wing loading of modern gliders (55+ kg/sqm vs 30-35kg/sqm for the 1960s ones) Still not useful for atmospheric reentry Happy 2024

Being utterly mesmerized by the parachutes interplay at the moment of splashdown "sparked joy" in this heart. Thanks Scott.

A skipping rock on a pond is one of the best visual analogies to reentry that I ever heard. Really helped me understand and visualize it after that.

Talked to a person who worked on the US X-15 rocket plane program (1959-1968). They considered putting the X-15 into orbit, but none of their pilots could fly the re-entry profile on the simulator without burning up. A non pilot member of the program asked if he could try re entry on the simulator, and they let him. He succeeded, and was able to repeat the manuever again and again. Everyone wanted to know how he was able to succeed where others could not. Simple, he said, he watched the temperature guage. If the X-15 got too hot, he pulled up; when it cooled down he let the plane descend. He did this over and over, and showed that winged reentry from orbit was possible. The X-15's glide ratio was about 4 to 1. Constructed of inconel X alloy. An ablative coating was tried on the X-15, but was found to be unsatisfactory, and actually interferred with the plane's natural ability to disapate heat.

As you were talking, I was thinking about inflatable or temporary heat shields that spread out and create more surface area. I hadn't heard about that at all. It's super cool that it's already been developed and put into testing. I'm excited to see where that technology goes.

I am amazed by the 'skipping' of Orion. The calculations to figure that out are truly incredible.

I never saw that re-entry footage before - my goodness, how amazing is that?!?! Thanks for going through the details of re-entry Scott, you answered all my questions on that topic in one short, concise and easy-to-understand video.

Short answer: it keeps space clean and free of as many bodies as possible. Long answer: the amount of thrust it would take to actually bring an object back in without a Dynamic Entry is roughly equivalent to half the thrust it took to put something up there but then you have to add thrust to putting the object and its return rocket up there. So for what's basically two tons of refined high-tech terracotta you can cut the price of the trip in half and look ballsy doing it.

Scott, what a great talk. I don't know how many stayed with you, but since I teach an engineering Thermo-Science lab,I was with you every step of the way. Great Job.