Yeah, it's really silly, but I've not heard it before.

Here was the question:
"How is it that 30 years ago we could do a soft touchdown on the Moon, but to land on Mars, they needed to wrap the craft in balloons?"

It went on to say that it seems like the balloon thing was a much better idea, and that there was no reason that people couldn;t survive a landing like the Mars Rovers did.

I didn't say it was good, just new.

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A Nerd can figure out how long it will take the original Enterprise traveling at warp 6.5 to travel from Regulus to Antares.
A Geek will think he can use that to pick up a girl in a bar.
A Dork knows he can't pick up the girl with it, but will hang around for hours anyway, just in case she asks.
She might. You never know.

I await the arrival of the well-clued-up BAUTers, but for now here's my thoughts:

1) Budget. They managed to land the Viking craft successfully without using balloons, but they were very expensive.

2) Light-lag. The turnaround time for the moon is about three seconds (one and a half seconds each way), and of course for the manned missions it wasn't an issue at all. Whereas on Mars it is never less than about six minutes (three minutes each way). It's not like a Space Lander game where you can use little thrusters to dodge the big spiky rock in realtime.

You're probably right about it being new - and not good! I'd not heard it before.

Hey, it beats the guy who wanted to know why they didn't use the same parachutes as helped with the return of the CM to Earth....

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"You keep using that word. I do not think it means what you think it means."

My first thought for the lack of balloons was the mass of the lander. Sure gravity is less, but that's still a lot of mass to bounce to a halt eventually, and with no atmosphere at all, I'd think it could roll for quite a while, and that's assuming the balloons held up to the initial impact. Plus, I've seen Johnny Knoxville movies. No one ever looks like they enjoy getting out of a tractor tire that rolled down a hill for 30 or so seconds.

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A Nerd can figure out how long it will take the original Enterprise traveling at warp 6.5 to travel from Regulus to Antares.
A Geek will think he can use that to pick up a girl in a bar.
A Dork knows he can't pick up the girl with it, but will hang around for hours anyway, just in case she asks.
She might. You never know.

I think you are on the right track. As I remember from some NOVA program or other, the mars lander hits fast and bounces hard. Even if they were strapped down these impacts would be from painful to actually dangerous to live astronauts.

And it's relatively new technology.

And they are still a bit in the "we hope this works" category on it. Seems it isn't quite as mature a technology as a nice descent engine.

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"You keep using that word. I do not think it means what you think it means."

Then, of course, there is the fact that Mars has a much higher gravity than the Moon, as well as an appreciable atmosphere, which makes a controlled unmanned landing much more difficult.
Secondly, the Apollo 11 landing for example was quite a close call, with only 30 seconds of fuel left. Armstrong took control of the craft after the guidance system was taking them own directly into a boulder field, which served to highlight the value of human control.
Thirdly, hardware can be built to withstand the rather vigorous impacts of a balloon landing and humans can't.
Fourthly, do these people have any idea of the actual size of the Mars rovers compared to the Lunar Module?
Finally, it's such a bizarre and lunatic idea, offering very poor odds at survival, it would never have been considered for a moment.

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This is not an idea to be tossed aside lightly - it should be thrown with great force

Sounds like the "questioner" doesn't have a firm grasp of the history of unmanned spacecraft. 30 years ago the Viking spacecraft performed a soft touchdown on Mars using the same "method" as the LMs.

The reason we have recently used "balloons" to soft land unmanned spacecraft on Mars is because it is cheaper than soft landing by retro rockets.

The first Russian unmanned moon landing, Luna 9, also used a balloon for the final impact, having used rockets to do most of the work. The later, heavier, Russian landers were pure rocket.

As with anything in engineering design, there are always tradeoffs. Balloons require less accuracy from the braking rocket control system, but they are heavier and also need an additional system to put the probe into an upright position after landing and balloon deflation.

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"The truth may be out there, but lies are inside your head" Terry Pratchett

The frustration for me is when people ask a question and the answer by definition has to be technical.

But the person who has asked the question has no concept whatsoever of Physics, ergo you have a Hitchers Guide scenario they don't understand the answer because they didn't understand the question.

Don't forget the fact that the balloons can't hit at full velocity. The craft needs to be slowed down first. On the moon, the only way to do this is with the rockets, so why not use the rockets all the way down.
On Mars, you have some atmosphere to assist you in slowing down.

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Numbers are not case sensitive. (me)

Then, of course, there is the fact that Mars has a much higher gravity than the Moon, as well as an appreciable atmosphere, which makes a controlled unmanned landing much more difficult.

But the atmosphere affords opportunities for control and braking, such as aerobraking, aerodynamic steering, and parachutes. When your goal is to dispose of orbital energy, having an atmosphere against which to drag is definitely an advantage.

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"Facts are stubborn things." --John Adams
Clavius Moon Base

But then I must ask - how high above the moon's surface does this alleged vacuum start?

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To the regular visitor of internet bulletin boards it is clear that it's an excellent idea your parents get to choose your real name.

If I though for an instant that anyone outside of this forum would find that funny, I'd get it on a shirt.

BTW, any chance someone with real power could run the thread title through the spell checker.

Maybe this is why there are no new ideas about the hoax. All the good ones have been taken and this is what's left.

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A Nerd can figure out how long it will take the original Enterprise traveling at warp 6.5 to travel from Regulus to Antares.
A Geek will think he can use that to pick up a girl in a bar.
A Dork knows he can't pick up the girl with it, but will hang around for hours anyway, just in case she asks.
She might. You never know.

But the person who has asked the question has no concept whatsoever of Physics...

And unfortunately he probably believes that no one else has a better grasp of it either. Sigh. There's a reason why rocket science is best left to the rocket scientists. Most of us are smart enough not to make handwaving assertions in fields we know little or nothing about.

I remember the executive board of a startup asking me to conduct a fairly innovative research and development project. They wanted as firm a date as possible for when it would be done. They didn't seem to understand that unprecedented development programs tend to defy reliable estimation. Finally one of them asked, "What kind of an engineer are you?" I'm sure my face reddened a bit, but I said, "So do you have a firm date for when the company will be profitable?" After hemming and hawing he told me he really couldn't tell, to which I asked rhetorically, "You mean there's uncertainty in what you do too?" I may not know much about corporate finance, but I know enough not to demand the unknowable from it.

Similarly, people have to decide whether they're going to make the effort to understand the problems that interest them, or whether they're going to trust the understanding of other people who know about it.

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"Facts are stubborn things." --John Adams
Clavius Moon Base

Hmmm. From this I must assume that some of the upper management of the company I work for, were working at that startup.

[Biting Tongue as not to compare Upper Management to HBs]

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Sic Transit Gloria Mundi

I remember a Dilbert cartoon where the pointy-haired boss walks into Dilbert's cubicle and says "I just realized I can double your workload and there's nothing you can do about it!" and then walked away

Pete

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PJE

There's so much I don't know about astrophysics. I wish I had read that book by that wheelchair guy.

He set his sights too low. Where I used to work that figure would be between triple and quadruple.

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A person's name, or a mark representing it, as signed personally or by deputy, as in subscribing a letter or other document.

"How is it that 30 years ago we could do a soft touchdown on the Moon, but to land on Mars, they needed to wrap the craft in balloons?"

Thirty years ago, the highly successful Vikings landed on Mars with rockets. No balloons.

It went on to say that it seems like the balloon thing was a much better idea, and that there was no reason that people couldn;t survive a landing like the Mars Rovers did.

The airbag rovers experienced something between 20 and 50 Gs at landing. (edit - see Mak's post below) Sojourner rover experienced around 20 Gs at landing. If he doesn't care what shape the crew is in, yeah, they'd likely survive it...

And the three rovers to date were much lighter than any manned vehicle.

I didn't say it was good, just new.

Ask this expert if he can understand that there might be more than one way to land on Mars. (In fact yet another, and entirely new, "skycrane" approach will be used for the upcoming MSL-09 rover.)

And remind him that Hollywood's spacecraft designers don't have to answer to the laws of physics.

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"Slapping a guy on the head is just as funny now as it was eighty years ago."

The questioner apparently forgot that Spirit and Opportunity also used parachutes and retrorockets as part of the landing procedure. Both MERs were IIRC designed to take up to 50gs on touchdown, but Opportunity experienced something like 2 to 3gs on landing, a soft one if you ask me.

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A person's name, or a mark representing it, as signed personally or by deputy, as in subscribing a letter or other document.