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With 2 mm/s^2 acceleration, Hermes' 124 day trip from Low Earth Orbit to Low Mars Orbit is impossible.

"Low earth orbit?" a Weir defender might object, "It's all hyperbolic fly bys."

Which is wrong, of course. The hyperbolic rendezvous were extraordinary maneuvers made under unusual circumstances (Watney needing rescue). The 124 day earth to Mars trip preceded the Sol 6 windstorm that stranded Watney. There aren't hyperbolic fly bys either at the beginning or end of this leg of the journey.

"The 124 day trip wasn't depicted in the movie". It was described in Weir's book as well as the movie's back story provided by Fox.

Also Neil DeGrasse Tyson's trailer for the movie. 1:15 of Neil Degrasse Tyson's trailer has Hermes departing from low earth orbit. 2:20 gives the trip at 124 days.

In addition here's a graphic from Inside Science (thank you Pearson Art Photo). I underlined the relevant phrase.

enter image description here

A Weir defender writes "The 124 day mission seems to not include LEO, but otherwise is fine."

This is like saying the 5 hour drive from Spokane Washington to Great Falls Montana seems to not include the Rocky Mountains but otherwise is fine.

The cities are 300 miles apart so a 5 hour drive seems plausible until you take into account that they're separated by the Rocky Mountains.

And so it is with the Hermes 124 day trip. When you're only accelerating 2 mm/s^2, getting out of LEO is huge. Here is an illustration from Mark Adler's answer to the Stack Exchange question General guidelines for modeling a low thrust ion spiral?General guidelines for modeling a low thrust ion spiral?

enter image description here

Mark Adler's description of above spiral:

Here is an example of a spiral from a circular orbit to escape (C3=0):

This is normalized to the starting circular orbit, where the distances are in units of the initial orbit radius, and the acceleration is constant at 10−3 of the gravitational acceleration of the body at the initial orbit radius. The total ΔV to escape is 0.856 of the initial orbit velocity, as compared to 1.0 for the rule of thumb. The total time to escape is 136 initial orbit periods. It goes around the body about 40 times before escaping.

In Hermes' case the 2 mm/s^2 constant acceleration would be about 2*10^-4 of the gravitational acceleration at the initial body radius, so the delta V would be more than .856 * 7.73 km/s. But I'll be kind and go with this under estimate.

.856 * 7.73 km/s is about 6.6 km/s. At 2 mm/s^2, it would take Hermes 3.3 million seconds to achieve this delta V. 3.3 million seconds is ~38 days. That leaves about 90 days to go from a 1 A.U. to a 1.52 heliocentric orbit. Which isn't doable at 2 mm/s^2 acceleration.

Most of that 38 days would be a slow spiral through the Van Allen Belts. Not only is the 124 day trip from LEO to LMO impossible, but it would also cook Watney and friends.

With 2 mm/s^2 acceleration, Hermes' 124 day trip from Low Earth Orbit to Low Mars Orbit is impossible.

"Low earth orbit?" a Weir defender might object, "It's all hyperbolic fly bys."

Which is wrong, of course. The hyperbolic rendezvous were extraordinary maneuvers made under unusual circumstances (Watney needing rescue). The 124 day earth to Mars trip preceded the Sol 6 windstorm that stranded Watney. There aren't hyperbolic fly bys either at the beginning or end of this leg of the journey.

"The 124 day trip wasn't depicted in the movie". It was described in Weir's book as well as the movie's back story provided by Fox.

Also Neil DeGrasse Tyson's trailer for the movie. 1:15 of Neil Degrasse Tyson's trailer has Hermes departing from low earth orbit. 2:20 gives the trip at 124 days.

In addition here's a graphic from Inside Science (thank you Pearson Art Photo). I underlined the relevant phrase.

enter image description here

A Weir defender writes "The 124 day mission seems to not include LEO, but otherwise is fine."

This is like saying the 5 hour drive from Spokane Washington to Great Falls Montana seems to not include the Rocky Mountains but otherwise is fine.

The cities are 300 miles apart so a 5 hour drive seems plausible until you take into account that they're separated by the Rocky Mountains.

And so it is with the Hermes 124 day trip. When you're only accelerating 2 mm/s^2, getting out of LEO is huge. Here is an illustration from Mark Adler's answer to the Stack Exchange question General guidelines for modeling a low thrust ion spiral?

enter image description here

Mark Adler's description of above spiral:

Here is an example of a spiral from a circular orbit to escape (C3=0):

This is normalized to the starting circular orbit, where the distances are in units of the initial orbit radius, and the acceleration is constant at 10−3 of the gravitational acceleration of the body at the initial orbit radius. The total ΔV to escape is 0.856 of the initial orbit velocity, as compared to 1.0 for the rule of thumb. The total time to escape is 136 initial orbit periods. It goes around the body about 40 times before escaping.

In Hermes' case the 2 mm/s^2 constant acceleration would be about 2*10^-4 of the gravitational acceleration at the initial body radius, so the delta V would be more than .856 * 7.73 km/s. But I'll be kind and go with this under estimate.

.856 * 7.73 km/s is about 6.6 km/s. At 2 mm/s^2, it would take Hermes 3.3 million seconds to achieve this delta V. 3.3 million seconds is ~38 days. That leaves about 90 days to go from a 1 A.U. to a 1.52 heliocentric orbit. Which isn't doable at 2 mm/s^2 acceleration.

Most of that 38 days would be a slow spiral through the Van Allen Belts. Not only is the 124 day trip from LEO to LMO impossible, but it would also cook Watney and friends.

With 2 mm/s^2 acceleration, Hermes' 124 day trip from Low Earth Orbit to Low Mars Orbit is impossible.

"Low earth orbit?" a Weir defender might object, "It's all hyperbolic fly bys."

Which is wrong, of course. The hyperbolic rendezvous were extraordinary maneuvers made under unusual circumstances (Watney needing rescue). The 124 day earth to Mars trip preceded the Sol 6 windstorm that stranded Watney. There aren't hyperbolic fly bys either at the beginning or end of this leg of the journey.

"The 124 day trip wasn't depicted in the movie". It was described in Weir's book as well as the movie's back story provided by Fox.

Also Neil DeGrasse Tyson's trailer for the movie. 1:15 of Neil Degrasse Tyson's trailer has Hermes departing from low earth orbit. 2:20 gives the trip at 124 days.

In addition here's a graphic from Inside Science (thank you Pearson Art Photo). I underlined the relevant phrase.

enter image description here

A Weir defender writes "The 124 day mission seems to not include LEO, but otherwise is fine."

This is like saying the 5 hour drive from Spokane Washington to Great Falls Montana seems to not include the Rocky Mountains but otherwise is fine.

The cities are 300 miles apart so a 5 hour drive seems plausible until you take into account that they're separated by the Rocky Mountains.

And so it is with the Hermes 124 day trip. When you're only accelerating 2 mm/s^2, getting out of LEO is huge. Here is an illustration from Mark Adler's answer to the Stack Exchange question General guidelines for modeling a low thrust ion spiral?

enter image description here

Mark Adler's description of above spiral:

Here is an example of a spiral from a circular orbit to escape (C3=0):

This is normalized to the starting circular orbit, where the distances are in units of the initial orbit radius, and the acceleration is constant at 10−3 of the gravitational acceleration of the body at the initial orbit radius. The total ΔV to escape is 0.856 of the initial orbit velocity, as compared to 1.0 for the rule of thumb. The total time to escape is 136 initial orbit periods. It goes around the body about 40 times before escaping.

In Hermes' case the 2 mm/s^2 constant acceleration would be about 2*10^-4 of the gravitational acceleration at the initial body radius, so the delta V would be more than .856 * 7.73 km/s. But I'll be kind and go with this under estimate.

.856 * 7.73 km/s is about 6.6 km/s. At 2 mm/s^2, it would take Hermes 3.3 million seconds to achieve this delta V. 3.3 million seconds is ~38 days. That leaves about 90 days to go from a 1 A.U. to a 1.52 heliocentric orbit. Which isn't doable at 2 mm/s^2 acceleration.

Most of that 38 days would be a slow spiral through the Van Allen Belts. Not only is the 124 day trip from LEO to LMO impossible, but it would also cook Watney and friends.

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With 2 mm/s^2 acceleration, Hermes' 124 day trip from Low Earth Orbit to Low Mars Orbit is impossible.

"Low earth orbit?" a Weir defender might object, "It's all hyperbolic fly bys, man!."

Which is wrong, of course. The hyperbolic rendezvous were extraordinary maneuvers made under unusual circumstances (Watney needing rescue). The 124 day earth to Mars trip preceded the Sol 6 windstorm that stranded Watney. There aren't hyperbolic fly bys either at the beginning or end of this leg of the journey.

"The 124 day trip wasn't depicted in the movie". It was described in Weir's book as well as the movie's back story provided by Fox.

Also Neil DeGrasse Tyson's trailer for the movie. 1:15 of Neil Degrasse Tyson's trailer has Hermes departing from low earth orbit. 2:20 gives the trip at 124 days.

In addition here's a graphic from Inside Science (thank you Pearson Art Photo). I underlined the relevant phrase.

enter image description here

A Weir defender writes "The 124 day mission seems to not include LEO, but otherwise is fine."

This is like saying the 5 hour drive from Spokane Washington to Great Falls Montana seems to not include the Rocky Mountains but otherwise is fine.

The cities are 300 miles apart so a 5 hour drive seems plausible until you take into account that they're separated by the Rocky Mountains.

And so it is with the Hermes 124 day trip. When you're only accelerating 2 mm/s^2, getting out of LEO is huge. Here is an illustration from Mark Adler's answer to the Stack Exchange question General guidelines for modeling a low thrust ion spiral?

enter image description here

Mark Adler's description of above spiral:

Here is an example of a spiral from a circular orbit to escape (C3=0):

This is normalized to the starting circular orbit, where the distances are in units of the initial orbit radius, and the acceleration is constant at 10−3 of the gravitational acceleration of the body at the initial orbit radius. The total ΔV to escape is 0.856 of the initial orbit velocity, as compared to 1.0 for the rule of thumb. The total time to escape is 136 initial orbit periods. It goes around the body about 40 times before escaping.

In Hermes' case the 2 mm/s^2 constant acceleration would be about 2*10^-4 of the gravitational acceleration at the initial body radius, so the delta V would be more than .856 * 7.73 km/s. But I'll be kind and go with this under estimate.

.856 * 7.73 km/s is about 6.6 km/s. At 2 mm/s^2, it would take Hermes 3.3 million seconds to achieve this delta V. 3.3 million seconds is ~38 days. That leaves about 90 days to go from a 1 A.U. to a 1.52 heliocentric orbit. Which isn't doable at 2 mm/s^2 acceleration.

Most of that 38 days would be a slow spiral through the Van Allen Belts. Not only is the 124 day trip from LEO to LMO impossible, but it would also cook Watney and friends.

With 2 mm/s^2 acceleration, Hermes' 124 day trip from Low Earth Orbit to Low Mars Orbit is impossible.

"Low earth orbit?" a Weir defender might object, "It's all hyperbolic fly bys, man!"

Which is wrong, of course. The hyperbolic rendezvous were extraordinary maneuvers made under unusual circumstances (Watney needing rescue). The 124 day earth to Mars trip preceded the Sol 6 windstorm that stranded Watney. There aren't hyperbolic fly bys either at the beginning or end of this leg of the journey.

"The 124 day trip wasn't depicted in the movie". It was described in Weir's book as well as the movie's back story provided by Fox.

Also Neil DeGrasse Tyson's trailer for the movie. 1:15 of Neil Degrasse Tyson's trailer has Hermes departing from low earth orbit. 2:20 gives the trip at 124 days.

In addition here's a graphic from Inside Science (thank you Pearson Art Photo). I underlined the relevant phrase.

enter image description here

A Weir defender writes "The 124 day mission seems to not include LEO, but otherwise is fine."

This is like saying the 5 hour drive from Spokane Washington to Great Falls Montana seems to not include the Rocky Mountains but otherwise is fine.

The cities are 300 miles apart so a 5 hour drive seems plausible until you take into account that they're separated by the Rocky Mountains.

And so it is with the Hermes 124 day trip. When you're only accelerating 2 mm/s^2, getting out of LEO is huge. Here is an illustration from Mark Adler's answer to the Stack Exchange question General guidelines for modeling a low thrust ion spiral?

enter image description here

Mark Adler's description of above spiral:

Here is an example of a spiral from a circular orbit to escape (C3=0):

This is normalized to the starting circular orbit, where the distances are in units of the initial orbit radius, and the acceleration is constant at 10−3 of the gravitational acceleration of the body at the initial orbit radius. The total ΔV to escape is 0.856 of the initial orbit velocity, as compared to 1.0 for the rule of thumb. The total time to escape is 136 initial orbit periods. It goes around the body about 40 times before escaping.

In Hermes' case the 2 mm/s^2 constant acceleration would be about 2*10^-4 of the gravitational acceleration at the initial body radius, so the delta V would be more than .856 * 7.73 km/s. But I'll be kind and go with this under estimate.

.856 * 7.73 km/s is about 6.6 km/s. At 2 mm/s^2, it would take Hermes 3.3 million seconds to achieve this delta V. 3.3 million seconds is ~38 days. That leaves about 90 days to go from a 1 A.U. to a 1.52 heliocentric orbit. Which isn't doable at 2 mm/s^2 acceleration.

Most of that 38 days would be a slow spiral through the Van Allen Belts. Not only is the 124 day trip from LEO to LMO impossible, but it would also cook Watney and friends.

With 2 mm/s^2 acceleration, Hermes' 124 day trip from Low Earth Orbit to Low Mars Orbit is impossible.

"Low earth orbit?" a Weir defender might object, "It's all hyperbolic fly bys."

Which is wrong, of course. The hyperbolic rendezvous were extraordinary maneuvers made under unusual circumstances (Watney needing rescue). The 124 day earth to Mars trip preceded the Sol 6 windstorm that stranded Watney. There aren't hyperbolic fly bys either at the beginning or end of this leg of the journey.

"The 124 day trip wasn't depicted in the movie". It was described in Weir's book as well as the movie's back story provided by Fox.

Also Neil DeGrasse Tyson's trailer for the movie. 1:15 of Neil Degrasse Tyson's trailer has Hermes departing from low earth orbit. 2:20 gives the trip at 124 days.

In addition here's a graphic from Inside Science (thank you Pearson Art Photo). I underlined the relevant phrase.

enter image description here

A Weir defender writes "The 124 day mission seems to not include LEO, but otherwise is fine."

This is like saying the 5 hour drive from Spokane Washington to Great Falls Montana seems to not include the Rocky Mountains but otherwise is fine.

The cities are 300 miles apart so a 5 hour drive seems plausible until you take into account that they're separated by the Rocky Mountains.

And so it is with the Hermes 124 day trip. When you're only accelerating 2 mm/s^2, getting out of LEO is huge. Here is an illustration from Mark Adler's answer to the Stack Exchange question General guidelines for modeling a low thrust ion spiral?

enter image description here

Mark Adler's description of above spiral:

Here is an example of a spiral from a circular orbit to escape (C3=0):

This is normalized to the starting circular orbit, where the distances are in units of the initial orbit radius, and the acceleration is constant at 10−3 of the gravitational acceleration of the body at the initial orbit radius. The total ΔV to escape is 0.856 of the initial orbit velocity, as compared to 1.0 for the rule of thumb. The total time to escape is 136 initial orbit periods. It goes around the body about 40 times before escaping.

In Hermes' case the 2 mm/s^2 constant acceleration would be about 2*10^-4 of the gravitational acceleration at the initial body radius, so the delta V would be more than .856 * 7.73 km/s. But I'll be kind and go with this under estimate.

.856 * 7.73 km/s is about 6.6 km/s. At 2 mm/s^2, it would take Hermes 3.3 million seconds to achieve this delta V. 3.3 million seconds is ~38 days. That leaves about 90 days to go from a 1 A.U. to a 1.52 heliocentric orbit. Which isn't doable at 2 mm/s^2 acceleration.

Most of that 38 days would be a slow spiral through the Van Allen Belts. Not only is the 124 day trip from LEO to LMO impossible, but it would also cook Watney and friends.

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Hermes makes aWith 2 mm/s^2 acceleration, Hermes' 124 day trajectorytrip from Low Earth Orbit to Low Mars Orbit. This orbit is implausibleimpossible.  

There seems to be some confusion about the departure"Low earth orbit. Some have argued there were?" a Weir defender might object, "It's all hyperbolic fly bys, man!"

Which is wrong, of Earth andcourse. The hyperbolic rendezvous were extraordinary maneuvers made under unusual circumstances (Watney needing rescue). The 124 day earth to Mars trip preceded the Sol 6 windstorm that stranded Watney. But theseThere aren't hyperbolic fly bys take place ineither at the latter partbeginning or end of this leg of the storyjourney. The

"The 124 day trajectory takes place prior to Watney getting strandedtrip wasn't depicted in the movie". It was described in Weir's book as well as the movie's back story provided by Fox. 

Also Neil DeGrasse Tyson's trailer for the movie. 1:15 of Neil Degrasse Tyson's trailer has Hermes departing from low earth orbit.

Departure from LEO is also in 2:20 gives the movie's backstorytrip at 124 days.

Crew readies for transport via traditional shuttle launch to rendezvous with the main vessel harbored in low orbit.

About 6 days after Mars arrival a windstorm hits and most the crew leaves. They ascend in a MAV to rendezvous with the Hermes. Later in the storyA Weir says MAVs are ordinarily designeddefender writes "The 124 day mission seems to deliver a 4.1 km/s delta V budget. To stick around Mars for 6 days and rendezvous the MAVnot include LEO, Hermes had to enter Low Mars Orbitbut otherwise is fine."

This establishes that Hermes did indeed leave Low Earth Orbit and arrived at Low Mars Orbit. Now here is what is wrong withlike saying the trajectory.5 hour drive from Spokane Washington to Great Falls Montana seems to not include the Rocky Mountains but otherwise is fine.

The cities are 300 miles apart so a 5 hour drive seems plausible until you take into account that they're separated by the Rocky Mountains.

Weir has said in several placesAnd so it is with the Hermes can accelerate at124 day trip. When you're only accelerating 2 mm/s^2. With this sort of acceleration it would take Hermes more than a month to spiral, getting out of earth's gravity well (most of that slow spiral would be through the Van Allen belts)LEO is huge. SeeHere is an illustration from Mark Adler's answer to the Stack Exchange question General guidelines for modeling a low thrust ion spiral?

For similar reasonsenter image description here

Mark Adler's description of above spiral:

Here is an example of a spiral from a circular orbit to escape (C3=0):

This is normalized to the starting circular orbit, where the distances are in units of the initial orbit radius, and the acceleration is constant at 10−3 of the gravitational acceleration of the body at the initial orbit radius. The total ΔV to escape is 0.856 of the initial orbit velocity, as compared to 1.0 for the rule of thumb. The total time to escape is 136 initial orbit periods. It goes around the body about 40 times before escaping.

In Hermes' case the 2 mm/s^2 constant acceleration would be about 2*10^-4 of the gravitational acceleration at the initial body radius, so the delta V would be more than .856 * 7.73 km/s. But I'll be kind and go with this under estimate.

.856 * 7.73 km/s is about 6.6 km/s. At 2 mm/s^2, it would take Hermes a week or two to spiral down3.3 million seconds to low Mars orbitachieve this delta V.

  3.3 million seconds is ~38 days. That leaves 80about 90 days to go from an onea 1 A.U. heliocentric orbit to a 1.52 A.U. heliocentric orbit. Which couldn't be done withisn't doable at 2 mm/s^2 acceleration.

Another unrealistic part isMost of that 38 days would be a slow spiral through the wind stormVan Allen Belts. Since Mars atmosphereNot only is near vacuum, the high winds would not threaten to topple the MAV. Weir has fessed up124 day trip from LEO to this errorLMO impossible, but it would also cook Watney and friends.

Hermes makes a 124 day trajectory from Low Earth Orbit to Low Mars Orbit. This orbit is implausible.  

There seems to be some confusion about the departure orbit. Some have argued there were hyperbolic fly bys of Earth and Mars. But these fly bys take place in the latter part of the story. The 124 day trajectory takes place prior to Watney getting stranded.

1:15 of Neil Degrasse Tyson's trailer has Hermes departing from low earth orbit.

Departure from LEO is also in the movie's backstory.

Crew readies for transport via traditional shuttle launch to rendezvous with the main vessel harbored in low orbit.

About 6 days after Mars arrival a windstorm hits and most the crew leaves. They ascend in a MAV to rendezvous with the Hermes. Later in the story Weir says MAVs are ordinarily designed to deliver a 4.1 km/s delta V budget. To stick around Mars for 6 days and rendezvous the MAV, Hermes had to enter Low Mars Orbit.

This establishes that Hermes did indeed leave Low Earth Orbit and arrived at Low Mars Orbit. Now here is what is wrong with the trajectory...

Weir has said in several places Hermes can accelerate at 2 mm/s^2. With this sort of acceleration it would take Hermes more than a month to spiral out of earth's gravity well (most of that slow spiral would be through the Van Allen belts). See General guidelines for modeling a low thrust ion spiral

For similar reasons it would take Hermes a week or two to spiral down to low Mars orbit.

  That leaves 80 days to go from an one A.U. heliocentric orbit to a 1.52 A.U. heliocentric orbit. Which couldn't be done with 2 mm/s^2.

Another unrealistic part is the wind storm. Since Mars atmosphere is near vacuum, the high winds would not threaten to topple the MAV. Weir has fessed up to this error.

With 2 mm/s^2 acceleration, Hermes' 124 day trip from Low Earth Orbit to Low Mars Orbit is impossible.

"Low earth orbit?" a Weir defender might object, "It's all hyperbolic fly bys, man!"

Which is wrong, of course. The hyperbolic rendezvous were extraordinary maneuvers made under unusual circumstances (Watney needing rescue). The 124 day earth to Mars trip preceded the Sol 6 windstorm that stranded Watney. There aren't hyperbolic fly bys either at the beginning or end of this leg of the journey.

"The 124 day trip wasn't depicted in the movie". It was described in Weir's book as well as the movie's back story provided by Fox. 

Also Neil DeGrasse Tyson's trailer for the movie. 1:15 of Neil Degrasse Tyson's trailer has Hermes departing from low earth orbit. 2:20 gives the trip at 124 days.

A Weir defender writes "The 124 day mission seems to not include LEO, but otherwise is fine."

This is like saying the 5 hour drive from Spokane Washington to Great Falls Montana seems to not include the Rocky Mountains but otherwise is fine.

The cities are 300 miles apart so a 5 hour drive seems plausible until you take into account that they're separated by the Rocky Mountains.

And so it is with the Hermes 124 day trip. When you're only accelerating 2 mm/s^2, getting out of LEO is huge. Here is an illustration from Mark Adler's answer to the Stack Exchange question General guidelines for modeling a low thrust ion spiral?

enter image description here

Mark Adler's description of above spiral:

Here is an example of a spiral from a circular orbit to escape (C3=0):

This is normalized to the starting circular orbit, where the distances are in units of the initial orbit radius, and the acceleration is constant at 10−3 of the gravitational acceleration of the body at the initial orbit radius. The total ΔV to escape is 0.856 of the initial orbit velocity, as compared to 1.0 for the rule of thumb. The total time to escape is 136 initial orbit periods. It goes around the body about 40 times before escaping.

In Hermes' case the 2 mm/s^2 constant acceleration would be about 2*10^-4 of the gravitational acceleration at the initial body radius, so the delta V would be more than .856 * 7.73 km/s. But I'll be kind and go with this under estimate.

.856 * 7.73 km/s is about 6.6 km/s. At 2 mm/s^2, it would take Hermes 3.3 million seconds to achieve this delta V. 3.3 million seconds is ~38 days. That leaves about 90 days to go from a 1 A.U. to a 1.52 heliocentric orbit. Which isn't doable at 2 mm/s^2 acceleration.

Most of that 38 days would be a slow spiral through the Van Allen Belts. Not only is the 124 day trip from LEO to LMO impossible, but it would also cook Watney and friends.

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