Mars Recon Orbiter Nearing Mars Orbit

DarkNemesis618 writes "The Mars Reconnaissance Orbiter, launched 12 August 2005, has nearly completed its 7 month journey to the Red Planet. At 9:24 pm GMT, the MRO is scheduled to fire its thrusters to slow it down enough to enter Mars orbit. NASA scientists are concerned about this final step for the orbiter as Mars has a history of 'swallowing' probes, orbiters, and landers sent to the Red Planet. What makes it more difficult is the delay time between NASA computers on earth and computers on board the orbiter. There is about a 12 minute delay between when data is sent from Earth to the time the orbiter's receivers pick it up, and vice versa. Because of this, onboard computers will handle the burn which adds to the risk."

Comments

Computerized burns

[donour]

Haven't orbital burns been computer controlled since the beginning human spaceflight. If I remember correctly, the manual burn during the Apollo 13 mission was not routine.

It isn't really a burn, but aren't all space shuttle landing corrections done by machine as well. I seem to remember reading that the shuttle had only been landed by hand once.

Re:Computerized burns

[MichaelSmith]

Haven't orbital burns been computer controlled since the beginning human spaceflight.

There is always a mix of manual and automatic control. On apollo 11 Mike Collins manually shut down the SM main engine at the end of the trans earth injection burn, not because the system wasn't going to do it automatically but because it made sense to back up the automated system.

All the apollo lunar landings were flown manually for the last minute or so. I don't know if you include this. My recollection is that shuttle landings are generally flown manually. As is usual there may be a mix of manual and automatic control. A bit like the autopilot takes care of basic control but the pilot can retarget the landing point if he wants to.

Re:Computerized burns

[AKAImBatman]

Haven't orbital burns been computer controlled since the beginning human spaceflight.

Pretty much. On most manned craft (going all the way back to Apollo), all the crew needs to do is punch in the preloaded program number, and the vehicle will attempt to do the rest. (That's why in the movies you always see the crew pull a booklet out before attempting a manuver. It's a list of program codes.) On the Space Shuttle, new telemetry can be uploaded by the ground crews. In theory, ground control is in a better position to compute an orbital burn.

The situation in this case isn't so much that it isn't automatic, as there's very little that can be done if things go wrong. By the time you know that something is wrong, the craft may have already burnt up. Even if it hasn't, by the time your response gets there, the craft could be in a completely unpredictable sitation.

With all the problems NASA and the ESA have had with losing craft, they always get a bit tense during orbital insertions and landing operations.

Re:Computerized burns

[AKAImBatman]

All the apollo lunar landings were flown manually for the last minute or so.

Actually, Armstrong took manual control from the computer during the Apollo 11 landing. This was due to several program errors (the radar switch was in the wrong position) as well as mistakes in automatic guidance. Armstrong was advised to abort at one point, but chose to land the Eagle anyway.

My recollection is that shuttle landings are generally flown manually.

Pretty much everything up until the landing gear is released is automatic. The Shuttle could be landed on automatic, but the engineers made an intentional decision to make the landing gear deployment a 100% manual process. The reason for this is that the landing gear cannot be stowed in flight once it is deployed. Should a computer error occur, premature deployment of the gear could cause a failed reentry or undershoot of the intended landing zone.

The Russians, OTOH, had no qualms about automating the landing. The Buran Space Shuttle flew once with no crew aboard, and safely landed on full automatic.

Re:Computerized burns

[MichaelSmith]

Armstrong was advised to abort at one point, but chose to land the Eagle anyway.

I don't see that in the ALSJ. They got a quantity light but Armstrong had the vehicle on the ground within the required 60 seconds. And in any event the low quantity was a consequence of sloshing in the tanks and Armstrong could feel the fuel sloshing around by that time. He knew the gauge was wrong.

The Shuttle could be landed on automatic, but the engineers made an intentional decision to make the landing gear deployment a 100% manual process. The reason for this is that the landing gear cannot be stowed in flight once it is deployed

As a result if they have to abandon a shuttle in orbit there is absolutely no way to recover the vehicle. Sure the landing gear should have a manual arm switch (there will be a breaker for it anyway), and during a normal manual descent it could be armed 10 seconds before deployment, but there must be hundreds of things which the computers could break during the flight which would cause loss of the mission.

Re:Something else they are worrying about

[MichaelSmith]

They won't know with absolute certainty that everything is ok until the time has passed and the probe comes around the planet.

Its a pity they couldn't organise a relay. There are two spacecraft in mars orbit right now which can relay comms from the ground. You would think that with a few software changes and a bit of planning one of them would be able to at least record telemetry from the spacecraft as it did the burn.

Re:Success!!!!

[DestroyAllZombies]

Well, thanks! I'm in the mission control area right now, so here's another score for slashdot. Of course the next six months of aerobraking will be the hardest, but being in orbit is fantastic.