Hacker News Reader

Comment by DanielBMarkham | Hacker News Reader

I remember the last lunar missions. We all thought that man would be going back to the moon within a few years or so.

Not the way it worked out.

Wellllll...

Pretty much the reason why a lot of progress in manned spaceflight came to a halt is due to the Shuttle program. It was sold on a laundry list of promises that somehow a lot of powerful folks utterly bought into. But in the end it ended up being far less capable and far more expensive than just about every alternative. Although admittedly it does look pretty cool.

Even the cool look holds a fatal flaw....never again will we design rockets where the cargo rides adjacent to the fuel, rather than on top.

It wouldn't be so bad if the orbiter didn't have such big wings (due to a military requirement for a large cross-range flight ability that was never actually used). Big wings means a more difficult reentry scenario, which means exotic, and brittle, thermal protection systems on the wing leading edges, which means a much larger area of highly vulnerable thermal protection materials on the orbiter. And it wouldn't be so bad if the vehicle didn't use liquid Hydrogen, which is super-cryogenic, requires excessive thermal insulation, and is extremely prone to formation of ice. A lot of people think that we were unlucky with the loss of Challenger and especially with the loss of Columbia, but in truth it was the opposite, we had gotten extraordinarily lucky prior to that. In reality the chances were very high that we would have lost a vehicle to either of those failure modes very much sooner.

But yes, it's a very troublesome design for a lot of reasons.

It's not really a question of wings so much as weight. The real issue with putting something on top is that what's below needs to carry that weight which is easier to avoid if the shuttle has it's own engines and sit's on the side. More importantly if the shuttle was not designed to send a few tones of stuff to orbit it could use the same basic design without experiencing anywhere near the same thermal stress and having a lot more safety margin.

It's not really a question of wings so much as weight.

The wings - because they were wings - were vulnerable to debris strikes during launch.

Which wasn't important during _launch_ but was sure a problem during re-entry.

Again, the thermal protection system was delicate because of weight issues. If the shuttles design goal was to get 20 people to LEO safely and they had anywhere close to the same budget to work with they could have used a few inches of titanium as part of the thermal protection system vs just glued on tiles that are less dense than Styrofoam.

PS: The surface area to weight is directly related to reentry heating. A person can do reentry in little more than one of those old style space suits and a parachute, the shuttle needed something that was barely possible to build.

Again, the thermal protection system was delicate because of weight issues.

I was not disagreeing with you.

* A person can do reentry in little more than one of those old style space suits and a parachute,*

Are you sure? If one is in orbit, one will re-enter hypersonic. This implies a whole lotta friction as you careen through the atmosphere.

Nitpick: It's not drag friction as much it was compressive heating. I suppose if you can avoid the compression, it wouldn't be as much of an issue...

Here is an example of a one man entry system consisting of nothing but a strap on heatshield and a retro-rocket gun: http://www.astronautix.com/craft/moose.htm

Here is an example

Heh - I've seen that before, or something like it.

But that's more involved than 'space suit, retro-rocket, parachute'.

Be a heckuva ride.

Yeah, the shuttles were designed as nuclear, space bombers.

The wings WERE a military requirement but nothing quite that silly. It was to enable a launch from Edwards AFB in California, insert or extract a polar orbit payload and land on US soil.

Importantly it allowed them to choose the orbital insert point while they were over US territory where nobody was watching precisely where it went.

Silly? It's a well known design requirement - the shuttle has to be able to enter the atmosphere, slow down and deliver a nuclear bomb over any target on Earth (e.g. Moscow).

Looks cool? You only need to look at it alongside the awesome Saturn rocket to see which is inferior. It is clearly the one involving assorted cans held together with the rubber bands.

Yup. It's odd that WW2 is closer to the moon landings than we are today.

Doesn't seem totally odd, given that the war was the inspiration for much of the technology involved, was the platform for many of the brains involved to perfect their craft, and ultimately created the geopolitical climate in which space technology was one of the more important tools of the emerging superpowers of the age.

Yes, and "space age materials" now invokes a feeling of being quite out of date.

Reply on news.ycombinator.com