Why NASA dropped idea of using MMU (Manned Maneuvering Unit)?

[Pawelk198604]

As above

[sevenperforce]

13 minutes ago, Pawelk198604 said:

As above

Too bulky, not necessary, replaced with the SAFER jetpack.

[DAL59]

2 hours ago, Pawelk198604 said:

As above

Tethered spacewalks are safer, so there was no point.

[NSEP]

From Wikipedia:

Quote

After a safety review following the Space Shuttle Challenger disaster, the MMU was judged too risky for further use and it was found many activities planned for the MMU could be done effectively with manipulator arms or traditional tethered EVAs.^[1] NASA also discontinued using the Shuttle for commercial satellite contracts, and the military discontinued the use of the Shuttle, eliminating the main potential uses. Although the MMU was envisioned as a natural aid for constructing the International Space Station, with its retirement, NASA developed different tethered spacewalk approaches.

It just wasn't usefull for anything. There wasn't anything the MMU could that all other systems couldn't.

They did however make a special version of the MMU called the SAFETY, wich serves as an emergency thing, just in case the astronaut falls into space.

 

The Russians also had an MMU-like system that they ditched. They went on using manipulator arms instead for transporting themselves (wich they apprently do, i first thought astronauts and cosmonauts have crawl to the place they had to fix but apperently their manipulator arms can transport them from place to place)

Edited August 17, 2018 by NSEP

[sevenperforce]

The one nice thing about the MMU was that an astronaut could use it to "fly out" and grab a derelict spacecraft and push it inside the orbiter's payload bay for repairs.

Or, you know, the orbiter could simply fly a little closer and grab the spacecraft with the Canadarm.

[Gargamel]

There's no current use for it.  They haven't dropped the idea, just shelved it until a need arises.  As mentioned above, there are alternatives.  So you can think of the MMU as just a prototype, and it's derivatives as backups to tethered EVA's.    But one day, it's successor will find it's niche and be used.  

[MaverickSawyer]

I suspect asteroid exploration will be one of the big uses for such systems... After all, the gravity is so low, yo can't walk, but rather than moving the entire ship to put a target of interest in reach of a manipulator arm, you just jet over and do what needs doing, then jet on back.

[kerbiloid]

So, KSP mechanical arm mods should add a command-seat-alike Kerbal-attaching ability, and Kerbal will no more need jetpacks, too.

On low-gravity bodies where you need a jetpack to move, you can just suddenly escape by an inaccurate shot.
So, mech arms with seats could be even more required.

[Gargamel]

19 hours ago, MaverickSawyer said:

I suspect asteroid exploration will be one of the big uses for such systems... After all, the gravity is so low, yo can't walk, but rather than moving the entire ship to put a target of interest in reach of a manipulator arm, you just jet over and do what needs doing, then jet on back.

That was my thought too.   If anybody has ever tried rock climbing or cave diving, you'll know that your guide ropes dragging on the rock surfaces causes a lot of friction, and can cut through a rope if your not careful.  A tethered EVA around an asteroid might not be practical at all, as you will possibly get it stuck on rock surfaces and a cut tether makes for a bad day. 

I wonder if you could create a weak "artificial gravity field" using gimballed thrusters.   You would orient yourself on the asteroid surface in a standing position, and then fire these thrusters, which would provide just a gentle force to keep you on the surface.  A gyroscope would keep the thrusters pointing in the same orientation as you work, keeping you on the surface.  They would be used similar to how a camera gimbal or Quadcopter gimbal works.  The thrust would be small enough to allow for a sufficient fuel supply. 

[sevenperforce]

20 hours ago, Gargamel said:

I wonder if you could create a weak "artificial gravity field" using gimballed thrusters.   You would orient yourself on the asteroid surface in a standing position, and then fire these thrusters, which would provide just a gentle force to keep you on the surface.  A gyroscope would keep the thrusters pointing in the same orientation as you work, keeping you on the surface.  They would be used similar to how a camera gimbal or Quadcopter gimbal works.  The thrust would be small enough to allow for a sufficient fuel supply. 

That's what they pretended to do in Armageddon.

[kerbiloid]

What to do just in a suit near an asteroid where you can fly away just after hitting it with a hammer?

[Gargamel]

2 hours ago, sevenperforce said:

That's what they pretended to do in Armageddon.

Oh god.... nevermind.... I never mentioned that. 

39 minutes ago, kerbiloid said:

What to do just in a suit near an asteroid where you can fly away just after hitting it with a hammer?

Drill and place a piton in the rock, and anchor in.  Then use the MMU to fly around when you want to move. 

[kerbiloid]

4 minutes ago, Gargamel said:

Drill and place a piton in the rock, and anchor in. 

+1

4 minutes ago, Gargamel said:

Then use the MMU to fly around when you want to move. 

Then just attach a tether to the hook.
Look at this asteroid just like at a horizontal mountain. Feel yourself alpinist.

A network of tethers where you can crawl around.

Edited August 19, 2018 by kerbiloid

[Gargamel]

21 minutes ago, kerbiloid said:

Then just attach a tether to the hook.
Look at this asteroid just like at a horizontal mountain. Feel yourself alpinist.

A network of tethers where you can crawl around.

As someone who has used a series of pitons and tethers on a rock face, I'd much rather have the ability to move around at will.   I'd rather consider it a bumpy field I can fly around. 

[kerbiloid]

5 minutes ago, Gargamel said:

As someone who has used a series of pitons and tethers on a rock face, I'd much rather have the ability to move around at will. 

Happily unlike a mountain the asteroid doesn't have a tangential force dragging you along the slope.
So, your muscular efforts are tiny, and the tethers wouldn't be tight.

And instead of spending and carrying balloons of propellant, all you need is

Spoiler

 

Edited August 19, 2018 by kerbiloid

[Gargamel]

1 minute ago, kerbiloid said:

 

And instead of spending and carrying balloons of propellant, all you needs is

  Hide contents

 

Why do you keep quoting this?!?  LOL

[kerbiloid]

?
I've quoted only "as someone ... at will"

P.S.
If U h8 "Snickers", there may b "Mars".

Edited August 19, 2018 by kerbiloid

[MaverickSawyer]

11 hours ago, Gargamel said:

Drill and place a piton in the rock, and anchor in.  Then use the MMU to fly around when you want to move. 

That only works if the asteroid is solid enough for the piton to set. What if the asteroid isn't that solid, or even little more than a floating gravel pile?

[mikegarrison]

10 hours ago, MaverickSawyer said:

That only works if the asteroid is solid enough for the piton to set. What if the asteroid isn't that solid, or even little more than a floating gravel pile?

You should try climbing in the Pacific Northwest. A lot of our "rock" is just like that.

[sevenperforce]

14 hours ago, MaverickSawyer said:

That only works if the asteroid is solid enough for the piton to set. What if the asteroid isn't that solid, or even little more than a floating gravel pile?

Gravel pile is the problem for sure. That's the reason to have an MMU.

[kerbiloid]

That's the reason to use a glue and make a bulky gravel anchor.

Edited August 20, 2018 by kerbiloid

[K^2]

Wasn't superglue vapor and sand one of proposed ways of rapid construction on Mars? If it works on Mars, it might work in total vacuum to keep a rock pile asteroid together. You'll need a lot of superglue, though.

[MaverickSawyer]

5 hours ago, mikegarrison said:

You should try climbing in the Pacific Northwest. A lot of our "rock" is just like that.

There's a significant difference between "friable" and "orbiting gravel piles".

24 minutes ago, K^2 said:

Wasn't superglue vapor and sand one of proposed ways of rapid construction on Mars? If it works on Mars, it might work in total vacuum to keep a rock pile asteroid together. You'll need a lot of superglue, though.

You'd need water present in some form, as that's the activator for cyanoacrylate-family glues, iirc.

[kerbiloid]

39 minutes ago, K^2 said:

Wasn't superglue vapor and sand one of proposed ways of rapid construction on Mars? If it works on Mars, it might work in total vacuum to keep a rock pile asteroid together. You'll need a lot of superglue, though.

Water is a superglue. too. It's cold there.

16 minutes ago, MaverickSawyer said:

You'd need water present in some form, as that's the activator for cyanoacrylate-family glues, iirc.

It's also an ice.

Spoiler

 

Edited August 20, 2018 by kerbiloid

[mikegarrison]

36 minutes ago, MaverickSawyer said:

There's a significant difference between "friable" and "orbiting gravel piles".

I don't know ... I've been on some stuff where you really can't tell the difference between where the rock ends and the scree begins.

Anyway, when rock anchors don't always work on rock right here, it's a sure bet they won't always work on rock in space either.