New Sweet way to reenter?

[garyw]

heating might be minimal but it's 6 hours of heating.............

 

[RisingFury]

And for this you have to spend 6 hours in the atmosphere, traveling around the world several times and increasing the chance of something going wrong.

Some very smart people at NASA though about this stuff for a long time and decided the way shuttle reenters now was the best choice for given technology.

 

[joiz]

so the shuttle is perfect and you would not do anything to improve it?

---------- Post added at 07:39 PM ---------- Previous post was at 07:37 PM ----------

in the early 20th century a group of really smart men got together and decided giant gas bags filled with hydrogen where the best way to cross the atlantic by air. but when one blew up and killed some people, they realised an emerging technology would do the job better and safer. the airplane.

 

[garyw]

so the shuttle is perfect and you would not do anything to improve it?

Nothing is perfect as has been tragically proven twice with the shuttle now

in the early 20th century a group of really smart men got together and decided giant gas bags filled with hydrogen where the best way to cross the atlantic by air. but when one blew up and killed some people, they realised an emerging technology would do the job better and safer. the airplane.

How many people have died in plane crashes versus ballon?

Even one of the safest, most modern commerical aircraft out there (the 777) has still suffered once crash because something was overlooked. Ice forming in a fuel pump.

In the case of the Hindenburg it wasn't the Hydrogen that caused the fire (FIRE not explosion), it was due to an electrostatic discharge which ignitied the coating of the zeppelin and that in turn caused the fire.

 

[TSPenguin]

in the early 20th century a group of really smart men got together and decided giant gas bags filled with hydrogen where the best way to cross the atlantic by air. but when one blew up and killed some people, they realised an emerging technology would do the job better and safer. the airplane.

Usaly Zeppelins were filled with helium and not hydrogen. And the experts advised against using hydrogen.
Too bad, the zeppelin is an awesome and relatively safe way to travel. Landing is a bit tricky though

 

[joiz]

Usaly Zeppelins were filled with helium and not hydrogen. And the experts advised against using hydrogen.
Too bad, the zeppelin is an awesome and relatively safe way to travel. Landing is a bit tricky though

yeah, i bet somebody advised NASA that hard reentry will cause strain on the delicate heat shield. woops. i was just pointing out that the big smart guy is not necesarily right. just look at global warming.

 

[chosen_silver]

I know it is perhaps not realistic given today's technology, but what kind thrust would be required to essentially stop a vehicle in orbit, so that it falls more or less straight down to the earth rather than relying on atmosphere to slow it down. Could it be done with some sort of controlled/directed explosion (ultra risky, i know)?

If there was some sort of system that could be developed (that woudl not destroy the vehicle in the process) it would completely eliminate any heating issues at all, and also allow for a very accurate landing zone.

 

[TSPenguin]

Stoping a vehicle that rapidly would destroy it for sure. And if you use some kind of rocket enginge, the weight would be far greater than a proper heatshield system.
Heating will occur nonetheless, after all you are falling down from pretty high up

 

[Sky Captain]

I know it is perhaps not realistic given today's technology, but what kind thrust would be required to essentially stop a vehicle in orbit, so that it falls more or less straight down to the earth rather than relying on atmosphere to slow it down. Could it be done with some sort of controlled/directed explosion (ultra risky, i know)?

If there was some sort of system that could be developed (that woudl not destroy the vehicle in the process) it would completely eliminate any heating issues at all, and also allow for a very accurate landing zone.

I think you mean powered descent. To do that you would need to carry nearly the same amount of propellant you used to take off thus heavily reducing payload mass. Craft with a nuclear lightbulb engine could do that although I`m fairly sure decent heat shield and wings to slow down in upper atmosphere would weigh less than needed propellant to stop you from orbital velocity.

When I flew first DGIV missions I accidentally blew a canopy while in orbit. I thought various ways how to save my crew then I realized I could dock with ISS, refuel and try a powered descent and I succeeded, no UMMU died because of my carelesness

 

[garyw]

yeah, i bet somebody advised NASA that hard reentry will cause strain on the delicate heat shield. woops. i was just pointing out that the big smart guy is not necesarily right. just look at global warming.

There is no strain on the Shuttle TPS during entry. Where do you get the thought that there is? There is HEATING but that's it. Would you say that your oven has strain because it's hot inside?

 

[Urwumpe]

yeah, i bet somebody advised NASA that hard reentry will cause strain on the delicate heat shield. woops. i was just pointing out that the big smart guy is not necesarily right.

The Shuttle has the same strain on the heat shield as Apollo. The only difference is, that the shuttle can slow down effectively at much higher altitude and can be designed with a much lighter heat shield. The TPS is about 20 times better, than what Apollo had, in terms of weight and costs.

Also, it is not about hard or soft reentry, but controlled reentry. The Shuttle has a smaller corridor for reentry than Apollo for returns from LEO, but this changes when you look at Apollo in it's designed mission of returning from the moon. During lunar returns, the Apollo heat shield has even less tolerance than the shuttle during it's reference mission.

The big smart guys on the shuttle did a good job regarding what the shuttle was meant to do. Politics wanted a spacecraft which can do it all and be cheap, and the engineers built a spacecraft which was a fair compromise between being cheap and doing it all. Which meant it was not really cheap, and it was not perfectly good in what it did. But it did it.

And after the last Shuttle retired, you will quickly see, that the Orion CEV is by no means a replacement for the Shuttle. It is like replacing an aircraft carrier by a rudder boat, because the rudder boat can also paddle through rivers.

Orion is for me the beginning of a new era of boredom. And it will take a while until the world will ever see something as capable as the shuttle again.

just look at global warming.

Looked at it. I have found many experts who know what they don't know. And many fools who believe what they think is always right.

---------- Post added at 07:06 PM ---------- Previous post was at 06:57 PM ----------

yeah, I agree with sky captain, von braun proposed reentering lifting body like ships heading back from the MOON not just orbit, they would reenter for 6 hours instead of 3 minutes, so the heating would be so minimal an X-15 could handle it.

Von Braun proposed such ships before humanity had even a vague understanding of hypersonic aerodynamics. All his aerodynamic estimates had been way too optimistic compared to what is possible in reality with optimized shapes.

 

[Linguofreak]

I know it is perhaps not realistic given today's technology, but what kind thrust would be required to essentially stop a vehicle in orbit, so that it falls more or less straight down to the earth rather than relying on atmosphere to slow it down. Could it be done with some sort of controlled/directed explosion (ultra risky, i know)?

If there was some sort of system that could be developed (that woudl not destroy the vehicle in the process) it would completely eliminate any heating issues at all, and also allow for a very accurate landing zone.

You wouldn't want to do it with an explosion, but even with a rocket it wouldn't really do you any good. The rocket engine would still produce heat, and for any rocket spunky enough to compete with a heat shield, the heating produced would likely be equal to or greater than that involved in aerobraking.

---------- Post added at 01:36 PM ---------- Previous post was at 01:16 PM ----------

yeah, i bet somebody advised NASA that hard reentry will cause strain on the delicate heat shield. woops. i was just pointing out that the big smart guy is not necesarily right. just look at global warming.

The Space-shuttle's heat shield is actually designed for a fairly soft reentry. And there are dangers from soft reentries as well as hard ones. With hard reentries you get high temperatures and aerodynamic forces. With soft reentries the temperatures are lower, but things still get hot, and stay hot for a longer period of time. Less energy goes into the air and more into the heat shield, so although the temperature is lower, the amount of heat you have to deal with is higher. And there's also more time for heat to bleed through the heat shield into the main body of the spacecraft.

 

[RisingFury]

yeah, i bet somebody advised NASA that hard reentry will cause strain on the delicate heat shield. woops. i was just pointing out that the big smart guy is not necesarily right. just look at global warming.

The heat shield ain't called the heat *shield* for nothing. It's DESIGNED to protect the Shuttle during reentry and is well suited to the temperatures it encounters. It was designed for this purpose and it's not at all problematic.

The only reentry failure that happened, happened because there was a huge hole in the shield that appeared at liftoff when a 0.8 kg piece of foam struck the wing at 800 km/h relative velocity.
But it's not like you can blame that on the heat shield. It's like putting the protective plates out of a bullet proof vest and then complaining why it didn't protect you from bullets.

 

[joiz]

when i say soft reentry i say a reentry so soft you don't even need a heat shield. but apparently that's not possible so

---------- Post added at 08:33 PM ---------- Previous post was at 08:30 PM ----------

There is no strain on the Shuttle TPS during entry. Where do you get the thought that there is? There is HEATING but that's it. Would you say that your oven has strain because it's hot inside?

my oven doesn't have to thoroughly checked every time I use it.

 

[Urwumpe]

my oven doesn't have to thoroughly checked every time I use it.

If you first let a pack of explosions explode next to it (SRB ignition transient), then throw some foam or ice at 800 km/h at it and later fire small bullets at 14 km/s at it, you will check your oven at least for being sure it still exists.

 

[joiz]

The Space-shuttle's heat shield is actually designed for a fairly soft reentry. And there are dangers from soft reentries as well as hard ones. With hard reentries you get high temperatures and aerodynamic forces. With soft reentries the temperatures are lower, but things still get hot, and stay hot for a longer period of time. Less energy goes into the air and more into the heat shield, so although the temperature is lower, the amount of heat you have to deal with is higher. And there's also more time for heat to bleed through the heat shield into the main body of the spacecraft.

read above (lets call it uber soft reentry) and: the shuttle TPS is so insulating it can be held in the hand after being put in an oven, so no concerns there. or few at least.

new question: what is this metalic heat shield that was supposed to be used by the SSTOs of the 90s? and wouldn't one of those stop this "new era of boredom"? and anyway, we should be seeing some interesting stuff, for example, in a couple of years no doubt we will see britney spears riding on ss2, that should raise interest from some people? and mayeb help fund making something intersting for the smart people too. I think being personally able to ride a spaceship will make up for the fact that people go to orbit in 60 technology.

 

[Bj]

my oven doesn't have to thoroughly checked every time I use it.

True, but your oven never gets anywhere near 2300 °F now does it?

 

[joiz]

True, but your oven never gets anywhere near 2300 °F now does it?

well that's sort of my point. I'm pushing towards no heat reentry, if indeed it is possible.

 

[Urwumpe]

well that's sort of my point. I'm pushing towards no heat reentry, if indeed it is possible.

Yes. If you do a propulsive reentry, slowing down to very low speeds and spend a lot of fuel countering gravity on the way.

 

[Ghostrider]

well that's sort of my point. I'm pushing towards no heat reentry, if indeed it is possible.

You are aware of the fact that the heat generated during re-entry is the vehicle's kinetic energy being converted into the aforementoned heat? And that is the only way to slow down from orbital velocity? When we have enough delta-V to have a spaceship land on its thrusters from orbit down, we'll have a no-heat reentry, until then we'll have to feel the heat.