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Mars mission-a grave problem

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  Mars mission-a grave problem Jackpol11@hotmail.com - 2016-03-02 11:40 -0500
    Re: Mars mission-a grave problem paparios <paparios@gmail.com> - 2016-03-02 09:52 -0800
    Re: Mars mission-a grave problem Tom Roberts <tjroberts137@sbcglobal.net> - 2016-03-02 12:10 -0600
      Re: Mars mission-a grave problem Emigdio Sophronius <emigg@augustvisitors.org> - 2016-03-02 20:41 +0000
        Re: Mars mission-a grave problem Jackpol11@hotmail.com - 2016-03-02 23:03 -0500
          Re: Mars mission-a grave problem Helénē Swanhild <helenes@gardenclosure.org> - 2016-03-03 20:39 +0000
    Re: Mars mission-a grave problem Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-03-03 22:57 +0100

#377731 — Mars mission-a grave problem

I don't see anything mentioned about the problem sending someone to
Mars. Presumably he would land at the closest approach of Mars.  Mars
period is 687 days, while Earth's is 365 days.
After landing, when Earth coincides with Mars, it races away around
the orbit ahead of the slower Mars. it will be 2.3 years before his
next trip back home.

The time required for the angular rate difference to accumulate to 2pi
is given by solving for T:
    2pi=(2pi/365 - 2pi/687)T 
1 = (1/365- 1/687)T = 1/778T
     T =778 days =2.3 years to next opposition

John Polasek

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#377738

On Wednesday, March 2, 2016 at 1:41:06 PM UTC-3, Jack...@hotmail.com wrote:
> I don't see anything mentioned about the problem sending someone to
> Mars. Presumably he would land at the closest approach of Mars.  Mars
> period is 687 days, while Earth's is 365 days.
> After landing, when Earth coincides with Mars, it races away around
> the orbit ahead of the slower Mars. it will be 2.3 years before his
> next trip back home.
> 
> The time required for the angular rate difference to accumulate to 2pi
> is given by solving for T:
>     2pi=(2pi/365 - 2pi/687)T 
> 1 = (1/365- 1/687)T = 1/778T
>      T =778 days =2.3 years to next opposition
> 
> John Polasek

This is already a well known problem, for decades. The best way of doing it depends on how short you want the total trip to last, or how long you want to stay on Mars. NASA engineers use a method of travel called a Hohmann Transfer Orbit - or a Minimum Energy Transfer Orbit - to send a spacecraft from Earth to Mars with the least amount of fuel possible. The technique was first proposed by Walter Hohmann who published the first description of the maneuver in 1925

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#377739

On 3/2/16 3/2/16 - 10:40 AM, Jackpol11@hotmail.com wrote:
> I don't see anything mentioned about the problem sending someone to
> Mars. Presumably he would land at the closest approach of Mars.  Mars
> period is 687 days, while Earth's is 365 days.
> After landing, when Earth coincides with Mars, it races away around
> the orbit ahead of the slower Mars. it will be 2.3 years before his
> next trip back home.

In the book/movie "The Martian", the planned duration of humans on Mars was just 
32 days, centered around closest approach. When Mark Watney got accidentally 
left behind, the limitations of orbital mechanics play a major role in 
complicating the rescue effort. (Of course this is Hollywood, and the rescue 
succeeds, just barely; the movie is in the trials and tribulations, which are epic.)

Just because YOU "don't see" something does NOT mean that nobody else has seen 
it. NASA mission planners will be far more aware of such things than a 
non-expert novelist....


Tom Roberts

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#377747

Tom Roberts wrote:

> In the book/movie "The Martian", the planned duration of humans on Mars
> was just 32 days, centered around closest approach. When Mark Watney got
> accidentally left behind, the limitations of orbital mechanics play a
> major role in complicating the rescue effort. (Of course this is
> Hollywood, and the rescue succeeds, just barely; the movie is in the
> trials and tribulations, which are epic.)
> Just because YOU "don't see" something does NOT mean that nobody else
> has seen it. NASA mission planners will be far more aware of such things
> than a non-expert novelist....

Does not really matter those orbits and distances. Constant speed burns no 
fuel. This is how they got it to the Moon, allegedly of course. In any 
case, I must insist, constant speed in vacuum burns no fuel. hence those 
distances are totally irrelevant.

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#377765

On Wed, 2 Mar 2016 20:41:57 +0000 (UTC), Emigdio Sophronius
<emigg@augustvisitors.org> wrote:

>Tom Roberts wrote:
>
>> In the book/movie "The Martian", the planned duration of humans on Mars
>> was just 32 days, centered around closest approach. When Mark Watney got
>> accidentally left behind, the limitations of orbital mechanics play a
>> major role in complicating the rescue effort. (Of course this is
>> Hollywood, and the rescue succeeds, just barely; the movie is in the
>> trials and tribulations, which are epic.)
>> Just because YOU "don't see" something does NOT mean that nobody else
>> has seen it. NASA mission planners will be far more aware of such things
>> than a non-expert novelist....
>
T
>Does not really matter those orbits and distances. Constant speed burns no 
>fuel. This is how they got it to the Moon, allegedly of course. In any 
>case, I must insist, constant speed in vacuum burns no fuel. hence those 
>distances are totally irrelevant.
This is not about burning fuel; it's about the problem of staying
there for any length of time, which in this case can be staying there
either for several days, or else for more than 3.2 years.

The closest approach distance is about 60,000,000 miles; compare this
with 250,000 miles to the moon. it's 240 times farther than the  moon.
240 X! That could make for fuel problem
There is a very nice animation of Earth and Mars orbiting, without any
orbital mechanics however. 
www.windows2universe.org/mars/mars_orbit.html
John Polasek

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#377817

Jackpol11 wrote:

>>Does not really matter those orbits and distances. Constant speed burns
>>no fuel. This is how they got it to the Moon, allegedly of course. In
>>any case, I must insist, constant speed in vacuum burns no fuel. hence
>>those distances are totally irrelevant.
> This is not about burning fuel; it's about the problem of staying there
> for any length of time, which in this case can be staying there either
> for several days, or else for more than 3.2 years.
> The closest approach distance is about 60,000,000 miles; compare this
> with 250,000 miles to the moon. it's 240 times farther than the  moon.
> 240 X! That could make for fuel problem There is a very nice animation
> of Earth and Mars orbiting, without any orbital mechanics however.
> www.windows2universe.org/mars/mars_orbit.html John Polasek

The point I guess was, that it does not really matter, since speed is
relative. The spaceship just needs to adapt its own speed to that planet
it intends to land on. Is not different than the good Russian rockets and
spaceships adapting their own speed to the International Space Station
(which between us, is a de-facto Russian Space Station (RSS)). Same
procedure. You leave Earth and adapt your speed correspondingly.

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#377825

Jackpol11@hotmail.com wrote:

> I don't see anything mentioned about the problem sending someone to
> Mars. Presumably he would land at the closest approach of Mars.  Mars
> period is 687 days, while Earth's is 365 days.
> After landing, when Earth coincides with Mars, it races away around
> the orbit ahead of the slower Mars. it will be 2.3 years before his
> next trip back home.
> 
> The time required for the angular rate difference to accumulate to 2pi
> is given by solving for T:
>     2pi=(2pi/365 - 2pi/687)T
> 1 = (1/365- 1/687)T = 1/778T
>      T =778 days =2.3 years to next opposition

This has nothing to do with the theory of relativity; it is off-topic here.  
It does not have anything to do with physics either, so it is off-topic in 
the entire sci.physics.* hierarchy.  The appropriate newsgroup for this 
subject is located in the sci.space.* hierarchy.  Thank you in advance for 
observing the rules.


PointedEars
-- 
Q: Why is electricity so dangerous?  
A: It doesn't conduct itself.

(from: WolframAlpha)

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