Mars probes orbit adjustment

[akron]

I am just curious if anyone knows if the current Mars orbiters have the capability to adjust their orbits and how much? I ask because I remember in the Martian (Which I understand is fiction, before you ask) they adjusted orbits in order to get more coverage of Mark's travels.

Is something like this theoretically, or literally, possible? In KSP, it takes a huge deal of dV to change an orbit inclination, which is why I'm wondering. I didn't think mission like this had a whole lot of fuel left for this kinda of maneuvers, just minor corrections and attitude control.

Edited March 21, 2016 by akron

[Scotius]

Missions of martian orbiters are planned for decades sometimes - it stands to reason they carry hefty amount of dV. Last year japanese Venus orbiter managed to enter the orbit using its RCS fuel reserve. Besides, with thin atmosphere of Mars, there is less need for station-keeping maneuvers than satellites around Earth must perform periodically.

[akron]

Just about how much dV would they carry though? I didn't think space agencies really placed that much extra fuel on a mission because of weight. A Far Cry from the generous dV I pack because of my terrible flying. From my reading, these kind of probes are not planned for more than a few years. They just get their missions extended for a long time. We kinda expect them to last much longer, based on previous experience and manufacturing quality, but they aren't exactly planned to (Based on their primary mission). Like Mars Global Surveyor had a close to two year mission, but got extended twice (or how the MER rovers had 90 day missions that lasted like 2600 days).

[KSK]

It's theoretically possible. From Wikipedia:

"On August 7, 1980 Viking 1 Orbiter was running low on attitude control gas and its orbit was raised from 357 × 33943 km to 320 × 56000 km to prevent impact with Mars and possible contamination until the year 2019. Operations were terminated on August 17, 1980 after 1485 orbits."

Plane changes at 56,000 km shouldn't require much delta-V.

I haven't looked at this in too much detail but both Mars Global Surveyor and Mars Reconnaissance Orbiter inserted into a highly eccentric orbit (minimum amount of delta-V expended to achieve capture) and then gradually aerobraked down to a lower, circular orbit. I wouldn't have thought they have the delta-V for any significant plane changes, although I don't know what sort of adjustments would be required in The Martian.

[KerbonautInTraining]

Adjustments to orbital period are very cheap and don't have a massive effect on the area they see, they do have a massive effect on when they see it. 

[akron]

16 minutes ago, KerbonautInTraining said:

Adjustments to orbital period are very cheap and don't have a massive effect on the area they see, they do have a massive effect on when they see it. 

Thanks. I didn't think about that. Or the aero capture that @KSK mentioned for initial insertion and dV saving.

I'll try and find a chart or calculate how much dV these had or have. Too much curiosity. If you can point me in a direction, I'd appreciate it! 

Edited March 21, 2016 by akron

[wumpus]

For "the Martian", I've heard (yes, I need to read that book, as well as see the movie) that the trip takes less than ~2.5 months, so they easily have the delta-v (having the life support is another issue.  Apollo certainly had the delta-v to afford "skipping off the atmosphere", but not the life support).

I remember reading (around ~2000ish) about a GTO satellite that was out of position, so (after dealing with insurance) looped it around the Moon to get it into proper insertion (of course, that probably didn't involve much attitude adjustment, but did take a chunk of delta-v).  No idea how much that effected the usable life expectancy (presumably it used the stationkeeping thrust), but it went from zero to non-zero.

[radonek]

wikipedia:

Quote

The spacecraft uses a 1,175 l (258 imp gal; 310 US gal) fuel tank filled with 1,187 kg (2,617 lb) of hydrazine monopropellant… Seventy percent of the propellant was used for orbital insertion,^[67] and it has enough propellant to keep functioning into the 2030s.

Dunno about deltaV, but should be significant with more then half of launch mass in hydrazine… AFAIK most probes of this kind are designed to hold enough fuel for stationkeeping and desaturation to last until reaction wheels wear out and break. So if NASA were willing to reduce lifespan or even write-off perfectly good probe to get better view of Mark (and book clearly states they are) they could make some changes. But if memory serves me correctly the book also states there is constellation of several satellites in orbit and maneuvers were more about synchronizing their over-head times into  continuous monitoring, so they would mostly do with slight period changes like Kerbonaut said.

[akron]

12 minutes ago, radonek said:

wikipedia:

Dunno about deltaV, but should be significant with more then half of launch mass in hydrazine… AFAIK most probes of this kind are designed to hold enough fuel for stationkeeping and desaturation to last until reaction wheels wear out and break. So if NASA were willing to reduce lifespan or even write-off perfectly good probe to get better view of Mark (and book clearly states they are) they could make some changes. But if memory serves me correctly the book also states there is constellation of several satellites in orbit and maneuvers were more about synchronizing their over-head times into  continuous monitoring, so they would mostly do with slight period changes like Kerbonaut said.

That makes sense. By my rough estimate, it seems like these missions carry a good amount of fuel for maneuvers. A lot seem to have enough to at least de-orbit at the mission's end. Makes me sad.

[fredinno]

 

6 hours ago, KSK said:

It's theoretically possible. From Wikipedia:

"On August 7, 1980 Viking 1 Orbiter was running low on attitude control gas and its orbit was raised from 357 × 33943 km to 320 × 56000 km to prevent impact with Mars and possible contamination until the year 2019. Operations were terminated on August 17, 1980 after 1485 orbits."

Plane changes at 56,000 km shouldn't require much delta-V.

I haven't looked at this in too much detail but both Mars Global Surveyor and Mars Reconnaissance Orbiter inserted into a highly eccentric orbit (minimum amount of delta-V expended to achieve capture) and then gradually aerobraked down to a lower, circular orbit. I wouldn't have thought they have the delta-V for any significant plane changes, although I don't know what sort of adjustments would be required in The Martian.

Mapping sats are always in polar orbits, so they need minimal inclination changes and can see everything on Mars. But Mars Probes can definitely last for a LONG time. Mars Odyssey is expected to be operational for up to 2025, meaning they have a LOT of propellant to keep up in Mars' atmosphere.

4 hours ago, akron said:

That makes sense. By my rough estimate, it seems like these missions carry a good amount of fuel for maneuvers. A lot seem to have enough to at least de-orbit at the mission's end. Makes me sad.

Well, all missions have to end at some point. Except for the Opportunity rover.