Moon and Mars landings?

Question

if man was able to land on the moon nearly 40 years ago in a craft that landed perfectly without any hitch,　why wasnt the same or better technology used for the rovers' (Spirit and Opportunity) landing? Instead of the airbag cushioned landing?
space engineers, any explanation? Thanks

Answer 1

Mars is a lot farther away than the moon, and we used a much smaller rocket to launch the rovers (because we don't make the Saturn 5 any more). That means that one of the primary considerations for spacecraft design is weight.

A rocket-braked landing takes a rocket, and a fairly large one, and it takes a lot of fuel. It is controllable, which is an advantage, but the price you pay is all that weight. An airbag is much lighter, and that means you can put more of the payload into the science package.

Answer 2

Actually, the airbag system is highly sophisticated--they couldn't have begun to build that 40 years abo.

As to why--the answer is simple--it cut the weight required considerably. Here's why: On the moon, you HAVE to use rockets to land--there's no atmosphere andthat's the only way to slow down. But that takes a LOT of fuel--and Mars has higher gravity.

But Mars also has a bit of an atmospherere. The rovers used that to brake out of Mars orbit (jsut the wa y the Apollo did and the Shuttle does). The atmosphere is so thin, though, that it levels out at about 900 mph. A special parachute then deployed (imagine designing a piece of cloth tha twill hold in a 900 mph wind!). Then the airbags were deployed at the last minute, after jettisoning the parachute.

Complicated--and like the parachute, all depended on extremely advanced design, mateerials, and computer controls. But--it probably cut the mass--and thus the cost--of getting the probes to Mars by at least half. Which is the main reason NASA could send two, instead of just one.

BTW--the lunar landings wernt all that smooth. The Appollo 11 mission neaarly didn't make it--the computer couldn't get a clear landing point. The were able to land only because Neil Armstrong pulled the stunt Luke Skywalker did in the Star Wars movie--only for real: he turned the computer off and landed manually. With just 10 seconds of fuel left in the tanks. No kidding!

Answer 3

Part of it is, as the other answerer mentioned, Mars has an atmosphere. Atmosphere's will cause friction which resists the descent of the craft, slightly altering it's course. While you can aerodynamically design a craft you can't account for wind speed and other such things since they'll be different by the time the craft gets there. Little things like that add up to make things difficult. The Moon, not having any appreciable atmosphere, would be reasonably easy to land on.

Also, the Moon missions were landed by humans who were actually "there" to make the adjustments in real time where as if you're trying to land a rover on Mars you're a few minutes behind what's actually happening (e.g. the video feed lags by a few minutes due to the distance so, while the video camera shows the craft at point "X" it's actually at point "Y" in reality). This means that you can't suddenly decide to make a subtle adjustment to the thrust, pitch, yaw, etc and expect it to happen like you could if you were landing on the Moon and you were physically in the craft. If it takes the video say, 5 minutes to get from the craft at Mars to NASA, then it'll take 5 minutes for the adjustment you send to it to get back. Add to that the time it takes to figure out what to do if what's happening wasn't expected and you'll start to see it's not quite as easy to land it as it was for the astronauts to land on the Moon.

Answer 4

If you think those landing went off without a hitch, that you are not aware of all the details. Apollo 11 had computer problems that almost caused the landing to be aborted just a few minutes before touchdown. They were also heading for a rock filled crater and Armstrong had to take over from the computer and to fly sideways so far to find a clear area that they almost ran out of fuel. A Mars rover could never do that, being under independent computer control and so far away from Earth that it took 20 minutes for a radio signal to reach it. But the air bags could land safely in rocky terrain that would be fatal to a lander with legs. And of course Apollo 13 never landed at all.

Answer 5

Mars has a substantially higher gravitational field also it has an atmosphere that would act as friction on any lander attempting to leave. So you'd need more powerful engines, more powerful engines = more weight, more weight = faster re-entry, faster re-entry = heavier heat shields, heavier heat shields = more weight (etc, etc, etc)

There was some discussion as to whether the lander on the apollo 11 moon landing, would sink into the lunar surface and Mike Collins was trained to fly back alone if need be. There was also a computer faliure on the same mission that left less than 10 seconds of fuel in the landers thrusters.

Answer 6

The Viking Mars lander missions in the 1970s did use rockets to land on the surface of Mars. Since that time, however, NASA's budget has been cut so they had to figure out more cost-effective ways of landing craft on Mars. The airbag landing method is simply a way of saving lots of money, money which can then be spent on the rovers themselves.

Answer 7

It maximizes the payload that NASA can send to Mars. The airbag system minimizes the amount of fuel needed to send a probe to Mars, so instead of fuel, there can be more scientific instruments. Good question.

Moon landing conspiracy theorists:

Before you try to mislead other people using bad science, do some research about your allegations. You'll see why the radiation that the astronauts received was not high enough to injure them and why the flag vibrated as it was stuck into the ground. There isn't a shred of scientific evidence against the landings. Honestly, if there was a conspiracy, scientists would be the first ones to pick up on it. Instead, scientists are the first to defend the landings. It should tell you something. I'm tired of seeing people spit upon the courage of the Apollo astronauts simply because they have a poor grasp of basic scientific principles.

Answer 8

The rover mission was remote.
Real time commands from the earth to the
Mars probe are to lengthy as to when to
commit a burn during a landing.
Also images coming back from the probe are to lengthy to adjust to real time events.
Engineers took into consideration of air bags as this method was the most practical,
for an unmanned mission.

Where as the moon landing was all done real time as the personnel was there to adjust their position avoiding a hard landing
resulting in damage.

Answer 9

Cost! Cost! Cost!

The lunar lander took a billion dollars to develop and build. It had to be guided precisely to dodge rocks, slopes and craters.

The rovers on Mars are not people. They can be bounced onto a planet inside a big ball. That probably would have killed a human.

When will people realise what we are - soft-bodied, water-based creatures. Space is incredibly alien. Men and women need billions of dollars of technology just to protect them in space. We need constant oxygen, food, water, air conditioning, hygiene, removal of body wastes, protection from radiation, heat, cold, hard landings, going stir crazy, etc etc etc

Simple as that. The current space program does as much as it can for the money that the govt is willing to allocate to NASA. At present that is not enough dollars to take humans beyond Earth orbit.

Answer 10

Everyone seems to have missed a major, very obvious point about why the landing techniques were different. The lunar missions were intended to be round trips, the Martian ones are not. Even discounting issues about atmoshpere, gravity levels, etc, the lunar missions required a soft landing, the Martian ones do not, so hard landing techniques are candidates.