using powerful laser technology

[keannu]

Does this "using" describe "method" or "scientists" as a present participle phrase(simultaneous action)? I think it's the latter, then what's the difference between without a comma(junk using) and with a comma(junk, using)? Is the latter a consecutive action?

ex)...Experts predict that Earth's orbit will be full of junk in 30 years if humans don't act now. Fortunately, scientists are working on a method to remove spece junk using powerful laser technology. Hopefully, space will be clean and safe again soon.

[JohnParis]

The method under development will use powerful laser technology...
Use relates to the method that the scientists are developing.
The commas are properly employed in the sentences you have provided.

[BobSmith]

[not a teacher]

With a comma,

"scientists are working on a method to remove space junk, using powerful laser technology"

suggests that the scientists are using lasers to develop the method, where the method may or may not include lasers. This doesn't make sense in this case. Maybe this example will make it more clear:

Without comma: "Architects are working on a method to build houses using powerful computer technology." – wait, build houses using what??

With comma: "Architects are working on a method to build houses, using powerful computer technology." – sounds reasonable.

In this case the comma is desired (unlike the original scientist example), because it makes the final phrase relate to the method, which is the correct intent.

[JohnParis]

Commas and their use are often the subject of lengthy discussion.

Here is a rather fun site that goes into great detail about commas and their use.
Rules for Comma Usage

John