Red Tether News Today

>> let me know when youre clear for me to start. >> reporter: traveling at 17,000 miles per hour, it was all business for astronauts jessica meir and christina koch, wearing the red tether replacing a failed power system on the space station. >> i have control of the battery. >> reporter: but todays milestone not lost on either woman. the first all-female space walk ever. >> we called ourselves space sisters because we were together really joined at the hip going through all the classes together...