After recovering first stage of Falcon-9 from last mission, SpaceX was waiting to perform static tests to confirm that everything is ready for next flight. Now we know - reusable technology is working!
Basically as we know, reusable technology is based on conception of using same first stage of the rocket in multiple launches. It is economically justified without any doubts. But to get as much as possible from implementing expensive technology in rockets used in commercial mission, first stage should be recovered undamaged - as Elon Musk mentioned repeatedly, whole procedure should looks like this: landing, testing, assembling with new second stage, refueling and launching. Time period when rocket is not used (and is not generating any income, but consuming resources) should be as short as possible. In case of any additional work around any part of recovered rocket this income is dramatically reduced. After first applause on 21 December 2015, many of us started to think if first stage would not become a monument of SpaceX technical capabilities and nothing more. Without official confirmation of positive results of technical inspection of the recovered stage full success was apparent.
On 15 January 2016 in Space Canaveral SLC -40 launch site started static test of propulsion. It was kind of these test, when interested person is holding breath. If propulsion would not work properly it would be sign that there is maybe a serious problem with engines, thrust control, fuel system or with general conception of using same rocket engine used for launch and landing. Fortunately, according Elon Musk Twitter:
"Conducted hold-down firing of returned Falcon rocket. Data looks good overall, but engine 9 showed thrust fluctuations."
"Maybe some debris ingestion. Engine data looks ok. Will borescope tonight. This is one of the outer engines."
So we now that generally propulsion is working. To show more precisely about which engine Elon Musk is considering, look at the picture below:
As You can see problem refers to one from eight engines. Problem was spotted during static test at SLC-40; previous inspection performed at SpaceX’s 39A complex at the Kennedy Space Center resulted only in small repairs. It seems that problems with one from outer engines will be subject of further analysis, but first stage looks to be in generally good condition. Test performed yesterday is second attempt of engines on SLC-40 and consisted ignition and hold-down firing. First one was planned for Thursday, but due the minor problems was postponed to Friday.