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

[kerbiloid]

If a gravel asteroid can't keep an ice anchor, how to drill it?
If no drilling - why need people?

P.S.
Say, you want a 1 t anchor (several times more massive than a spaceman).
Rocks density ~2.5 t/m³, so you need ~0.4 m³ of stones..
Say, stones are round and fill 75% of volume. So, you need ~0.15 m³ of water per anchor.
Anchor volume ~0.55 m³

10 t of water ~= 60 anchors with total mass ~70 t.

Edited August 20, 2018 by kerbiloid

[Greenfire32]

No practical use and tethered space-walks are far safer because you don't risk drifting off into the black (or worse, into the blue...).

That said, it would be cool if they could miniaturize the MMU and add it to the spacesuit as kind of a "oh crap, your tether snapped and you're drifting away! Use a rescue burst!" kind of thing.

[sevenperforce]

1 hour ago, Greenfire32 said:

That said, it would be cool if they could miniaturize the MMU and add it to the spacesuit as kind of a "oh crap, your tether snapped and you're drifting away! Use a rescue burst!" kind of thing.

That is what they did.

[Greenfire32]

15 hours ago, sevenperforce said:

That is what they did.

oh neat. I had no idea.

[kerbiloid]

Another idea about ice anchors: stick a stick where you want another anchor, then set a water hose into the ground and pour the water under pressure.
It will first get down vertically, then spread aside.
When the water gets frozen, you have an overturned ice-and-gravel underground mushroom with a cubic meter of stones on top of it.

Attach a rope to the stick sticking out of the anchor. Connect multiple anchors with ropes.

Edited August 21, 2018 by kerbiloid

[magnemoe]

18 hours ago, Greenfire32 said:

No practical use and tethered space-walks are far safer because you don't risk drifting off into the black (or worse, into the blue...).

That said, it would be cool if they could miniaturize the MMU and add it to the spacesuit as kind of a "oh crap, your tether snapped and you're drifting away! Use a rescue burst!" kind of thing.

Also with the shuttle you could use rcs and pick up the stranded astronaut, this is not an option with ISS. 
For work on an space station you would probably want to be tethered anyway, and yes as sevenperforce posted they have an backup system. 
Assume they use an buddy system for spacewalks, unlike for diving its probably a bit limited that the buddy can do outside of helping the astronaut with problems into the airlock, but with glove or visor problems this would be needed.