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Delta II Countdown
The Launch of MER-B "Opportunity"
by Stephanie Wong

MER-B was launched on the Delta II Heavy, a vehicle with slightly larger booster rockets than its cousin, the Delta II, which launched MER-A.  It was a long wait for the Heavy's maiden flight.  After two weeks of delays with the weather and launch vehicle problems, Opportunity finally lifted off at 11:18 p.m. EDT, July 7, 2003, on Pad 17-B.  It sailed out to space with the hopes and dreams of the engineers who built the spacecraft, the scientists who want to learn about the universe, and the entire world's spirit in discovery and exploration.  Getting to Mars is not easy.  Launching a spacecraft is a well-choreographed dance that requires precision, accuracy, smarts and dedication.  Many have been waiting for years for this moment, and we congratulate the launch team for a job well done.  Each and every launch is exciting, and this one was no different.  Go Opportunity!

21/6/03 The payload fairing is secured around the spacecraft.  It protects the payload as the rocket ascends through the thick atmosphere.  This is the last time we see the spacecraft on Earth.   Spacecraft Closeout
28/6/03 A view of the complete rocket stack.  There are 9 solid rocket motors, seen attached to the first stage, that help propel the MER rover into space.  Six are ignited at liftoff and the last three are ignited when ground-lit ones burn out.   Bottom-up view of the solid rocket motors stacked around the booster stage
7/7/03 A string of problems with the launch vehicle delays the launch of Opportunity.  But at this point, everything looks like a go, and the launch teams prepare for an ontime liftoff.  
7/7/03 Terminal Countdown is initiated at T minus 150 seconds.  The Launch Manager and Boeing Mission Director polls their launch team and they are all go for launch.  They begin tanking procedures.  
T-95 minutes: Weather appears to be a go.
T-30 minutes: Main engine gimbal checks are being made to see if the first stage can steer itself.
T-20 minutes: We have a go for countdown resume.
T-10 minutes: Fuel tanks are pressurized.
T-6 minutes: Spacecraft goes to internal power.
T-4 minutes: Final poll.  We are go for launch.
T-7 seconds: Countdown has been halted due to trouble with a liquid oxygen (LOX) fill and drain valve.
  Venting of condensate after cryogenic tanking
T-4 minutes and holding: Launch is recycled for 2nd launch attempt.  Troubleshooting of the fill and drain valve underway.  If checks are successful, countdown will resume at T-4 minutes.
T-4 minutes: Checks are successful and countdown resumes.
T-1 minute: Delta II is on internal power.
T-10 seconds: 10... 9... 8... 7... 6... 5... 4... 3...
T-2 seconds:
"Main engines start...
  Main engines start
"Zero!  And liftoff of the Delta rocket with Opportunity.  A chance to explore and unlock the secrets of our neigbouring planet."  
At liftoff, the first stage and booster rockets combine to produce about a million pounds of thrust, accelerating from 0 to 4000 kilometres per hour in about a minute.  
If watching the launch live in person, the light of the rocket reaches you before the sound does.  Particularly at night, the entire sky glows a bright orange, and suddenly, there is this giant rumble that hits.  There is nothing you can do but to follow the rocket's trail in awe and silence:  
The vehicle has cleared the tower.  
T-29 seconds: Mach 1, the speed of sound, is reached.  
T+80 seconds: The six ground-lit boosters burn for 75 seconds before they are jettisoned in threes, one second apart.  Prior to jettison, the air-lit solid motors are ignited.   Booster Separation (Spirit)

For about 1 1/2 minutes the booster stack continues to burn until they too are jettisoned.  In another 2 minutes, we have Main Engine Cutoff (MECO), where the first stage shuts down, separates, and the second stage is ignited.  As the Delta II leaves Earth's atmosphere, there is no need to protect the tiny spacecraft inside, so the fairing is jettisoned.  Within 9 minutes of flight, we have SECO-1 (1st Second Stage Cutoff).  At this time, Opportunity coasts around Earth for 60 minutes, unpowered, getting into the right orbital position for its final boost to Mars.  For most of this coast, MER-B is in a communications blackout until it is picked up by a tracking station in the Pacific.  Now over the Pacific Ocean, the second stage reignites for a short burn until SECO-2.  Since the third stage does not have the equipment to stabilize itself during flight, it instead has spin rockets to spin the spacecraft like a spinning top so that as it's firing, it maintains a straight course.  After spin-up, the second stage separates and the third stage with the spacecraft fires off to Mars!  Yo-Yo despin weights are deployed to slow down the spacecraft's spin, and then we have spacecraft separation from the third stage.  About 80 minutes after launch, Opportunity is on its 6-month cruise to the Red Planet.

The four Marsbound spacecraft, on their trajectories, as of August 3, GMT.

Photo Credit: All images courtesy of NASA, except for the booster separation picture, which is credit Dan Maas (Maas Digital), Ecliptic Enterprises Corp., Boeing, and NASA; and the Solar System Simulator animation, which is credit NASA/JPL.
References: JPL-MER homepage, Boeing MER-B Media Kit, Spaceflight Now, KSC MER-B Virtual Launch Control Center.

- 4 August 2003

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Last Updated:
4 August 2003


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