Remember that probeon the top of the rocket? It’s still being watched carefully today, and notjust because of its hard-to-remove cover.
As we noted yesterday, the five-hole probe is a very important set of sensorsfor collecting aerodynamic data during the flight. It remained covered whileAres I-X was rolled out to the launch pad and just prior to launch because theavionics team did not want water, bugs, bird messes, or other debris getting onor in the sensors. Inside the five holes is a diaphragm of flexible materialagainst which air vibrates to produce data. If water or foreign object debris(FOD) gets onto the diaphragm, there is a risk that the data from the sensorscould be harder to interpret after the flight. Once the Ground Operations teamremoved the cover, there is no way to put it back on short of rolling therocket back into the Vehicle Assembly Building. The I-X team knew this mighthappen, but now that the cover is off, what next? Just to add to the challenge,Cape Canaveral expected (and got) an inch and a half of rain on Tuesday night.
What NASA did was take a spare five-hole probe out to the pad, put it on thefixed service structre and gave it a similar exposure to rain as the flighthardware. The spare unit was tested before and after the rain to determine itseffects on the sensors’ behavior. In this way, NASA will be able to account forany changes in sensor measurements due to water on the sensor and use thatinformation to interpret the data after the flight. This is just one of manylessons the Ares team is learning as it continues testing on the Ares I-Xrocket.