Go, go Phoenix! 18 hours until launch...
Posted By Emily Lakdawalla
2007/08/03 09:55 CDT
Well, here we go; the once-every-two-year event of a spacecraft deprarture from Earth toward Mars is less than a day away, weather permitting. The original launch date (today) would have given my daughter the biggest candle ever to light her first birthday cake, but that was not to be. Now I REALLY hope that the launch will go off tonight, if only for the selfish reason that I do not want to have to wake up more than once at 2 in the morning to see if the thing is really going to go. (Once upon a time, I would have stayed up to watch the launch, but with at least one family member going to bed at 7:30 it now seems a better plan to try to get a few hours' sleep in before the rocket ignites.)
I went through the Phoenix mission press kit yesterday in an attempt to compose a timeline for the launch story that Amir Alexander posted but I'm afraid that details on the timing of launch events were unusually scanty. The best I can do is to take the launch timeline I wrote for Dawn -- which has the same exact events, though not the same exact durations -- and fill in the few skimpy timing details that were provided in the Phoenix press kit. So here you go.
|Time (EDT)||Time (UTC)|
The launch window is about 27 minutes long. At liftoff, the first stage of the rocket and six of the nine solid rocket boosters ignite.
|First six solid rocket boosters burn out|
The first stage of the rocket is still firing as the six solidsburn out.
|Remaining three solid rocket boosters ignite|
|Burned-out solids separate|
This happens as the first stage and three solids continue to fire. The separation of the six burned-out solids happens three at a time, with one second elapsing in between the separation events.
|Remaining three solids burn out|
|Remaining solids separate|
The last of the solid rocket boosters fall off as the rocket passes through an altitude of 73 kilometers (45 miles).
|First stage shutoff|
The main engine cuts off as the rocket passes through an altitude of about111 kilometers (69 miles).
|First stage separation|
|Second stage ignition|
|Payload fairing jettison|
The nose cone of the rocket splits in half and falls away,and the Phoenix spacecraft is exposed to space for the first time.
|Second stage shutdown|
Thereis a pause in the middle of the firing of the second stage; the spacecraftcoasts until it has reached exactly the right position in Earth orbitto begin the journey to Mars.
|Second stage restart||about 72||06:39||10:39|
|Second stage shutdown||about 74||06:41||10:41|
|Thrusters spin up the spacecraft to 70 revolutions per minute|
The spacecraft is spun in order to stabilize it for its onward journey.
|Second stage separation|
|Star 48 upper (third) stage ignition|
At last, Phoenix will fly fast enough to escapeEarth's gravity and head into interplanetary space.
|Star 48 burnout|
|Spindown to zero|
Ayo-yo despin system will counteract the spacecraft's spin.
|Third stage separation|
The spent third stage falls away at an altitude of 1,016 kilometers (631 miles).
|Goldstone DSN station establishes communication |
After waiting a little more than 8 minutes for the liquid xenon to swirl to a stop, the spacecraft's hydrazine attitude-control thrusters will counteract whatever spin the spacecraft gained from the process.