Thrust enhancement

[tinlail]

The late Len Cormier looked at LOX injection for the DARPA/RASCAL project http://web.archive.org/web/20070519031526/http://tour2space.com/archives/f-14lv/f-14-st.htm has some pictures, (which is what I can understand). Searching for that might give you greater information of the limitations of the technology.

[rickshaw]

...and makes LOTS of smoke! 

B-47s and early 707s and DC-8s used that technique as I recall. The SAC even had to modify its massed take-off procedures because there was so much water injection induced smoke on the runway the following aircraft couldn't see well enough to take-off!

If one watches the old movie "Gathering of Eagles" with Rock Hudson and Rod Taylor.  You can see its effects in this clip of a "minimum interval take off"   http://www.youtube.com/watch?v=Cq6Hpxyrhyo&feature=related