3 years for a man to get to and from Mars?

Just was reading on the space dot com website that it will be a three year
mission when and if we send men to Mars.

But when I was watching the animation of the Spirit and Opportunity missions
it said it took 7 months for the rover to get to Mars.

Assuming that the Astronauts spend 2 weeks on Mars That is still only 14-1/2
months round trip.

Why will it take so much longer for men to get to Mars then Machines?

Thanks.

"Doctor Bombay" wrote in
:

Just was reading on the space dot com website that it will be a three
year mission when and if we send men to Mars.

But when I was watching the animation of the Spirit and Opportunity
missions it said it took 7 months for the rover to get to Mars.

Assuming that the Astronauts spend 2 weeks on Mars That is still only
14-1/2 months round trip.

Why will it take so much longer for men to get to Mars then Machines?

One, the MER rovers weren't pushing the capabilities of the rockets that
sent them to Mars. So it was possible to use a slightly faster trajectory
than the 258 days that a classical Hohmann transfer would provide. A human
mission would be much more massive, so providing that same level of margin
would be more expensive.

Two, the robots don't have to return. The humans must wait until the
planets are aligned properly for the return trip. That won't happen in two
weeks. Generally, the first opportunity is in about 90 days, but requires
an indirect trajectory that takes longer than a Hohmann transfer. A direct
return requires a longer surface stay, up to one year.


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Just was reading on the space dot com website that it will be a three
year mission when and if we send men to Mars.

But when I was watching the animation of the Spirit and Opportunity
missions it said it took 7 months for the rover to get to Mars.

Assuming that the Astronauts spend 2 weeks on Mars That is still only
14-1/2 months round trip.

Why will it take so much longer for men to get to Mars then Machines?

One, the MER rovers weren't pushing the capabilities of the rockets that
sent them to Mars. So it was possible to use a slightly faster trajectory
than the 258 days that a classical Hohmann transfer would provide. A human
mission would be much more massive, so providing that same level of margin
would be more expensive.

Two, the robots don't have to return. The humans must wait until the
planets are aligned properly for the return trip. That won't happen in two
weeks. Generally, the first opportunity is in about 90 days, but requires
an indirect trajectory that takes longer than a Hohmann transfer. A direct
return requires a longer surface stay, up to one year.

Ah I see. They need to spend more time on the surface of Mars so the planets
will bi in the proper orbit .

That make sense. THANKS!!!

BTW what does that word "Hohmann" mean? Is it an acronym?

"Doctor Bombay" writes:
Ah I see. They need to spend more time on the surface of Mars so the planets
will bi in the proper orbit .

That make sense. THANKS!!!

BTW what does that word "Hohmann" mean? Is it an acronym?

Named after the guy that discovered it, a Hohmann transfer orbit is
the most efficient (lowest fuel consumption) orbit moving from one
circular orbit to another.

To be technical, a Hohmann orbit is an ellipse with periapsis at
the smaller radius and apoapsis at the larger radius... so to actually
use it you have to wait until the planets are in the right positions,
which happens every two years or so, and they aren't symettric
(i.e.when the planets are set right to send a probe to Mars, you'll
have to wait even longer once the probe is there for the right
alignment to get back).

There are many other transfer orbits you can do, but they all
require more fuel.


--
Richard W Kaszeta

http://www.kaszeta.org/rich

"Doctor Bombay" wrote in message
...
| Just was reading on the space dot com website that it will be a three year
| mission when and if we send men to Mars.
|
| But when I was watching the animation of the Spirit and Opportunity
missions
| it said it took 7 months for the rover to get to Mars.
|
| Assuming that the Astronauts spend 2 weeks on Mars That is still only
14-1/2
| months round trip.
|
| Why will it take so much longer for men to get to Mars then Machines?
|
| Thanks.
|
|
|
|
Well, at the time the rovers went, the Earth and Mars were converging, and
on the same side of the Sun. Mars is now receding again, as the Earth takes
less time to go around the Sun.

Assuming you want a decent time on Mars, and not just a touch and go visit,
buy the time you wanted to come back, the Earth an Mars would be moving away
from each other, or, you could go when the Earth and Mars were still
converging, but still a long way apart, in which case the trip out would be
longer than the trip back.

If you want short trips both ways, you need to wait on Mars, until the right
part of both orbits again, hence the Three years.

So, Problems with a long trip out.
Long period of weightlessness
Need more consumables,
More chance of problems.

Long trip back much the same problems, made worse by having to do this after
getting to Mars in the first place.

Problems with long stay on Mars, Supplies again of course, but I'd imagine
that supplies and living systems would be robotically put there before the
mission.

Brian

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Richard Kaszeta wrote:
"Doctor Bombay" writes:
Ah I see. They need to spend more time on the surface of Mars so the planets
will bi in the proper orbit .

That make sense. THANKS!!!

BTW what does that word "Hohmann" mean? Is it an acronym?

Named after the guy that discovered it, a Hohmann transfer orbit is
the most efficient (lowest fuel consumption) orbit moving from one
circular orbit to another.
snip
There are many other transfer orbits you can do, but they all
require more fuel.

Unless there are other bodies to interact with, in which case maybe not.

Unless there are other bodies to interact with, in which case maybe not.

Well the whole purpose of that nuclear booster stage was to cut transit time to
2 or 3 months each way? I dont think a 3 year trip is a viable idea. Beyond
which they should build a sooped up emergency supply vehicle for have to have
stuff that could cut that time even futher. It would need radiation shielding
for the crew so it could be light weight too. for faster journeys

"Doctor Bombay" wrote in message ...
Just was reading on the space dot com website that it will be a three year
mission when and if we send men to Mars.

But when I was watching the animation of the Spirit and Opportunity missions
it said it took 7 months for the rover to get to Mars.

Assuming that the Astronauts spend 2 weeks on Mars That is still only 14-1/2
months round trip.

Why will it take so much longer for men to get to Mars then Machines?

Thanks.

Three years stuck inside a can feels more like a prison sentence than
a honorary mission.

We should compare this to sea ships in the 19th century regular ships
usually takes around 6 months from Hong Kong to New York, while fast
clipper ships usually took around 3 months from one destination to
another destination.

http://baegis.ag.uidaho.edu/~myron/html/clipper.htm

Of course how much time it takes depends on the destination and the
conditions.

It also should be mentioned sea voyaging ships usually had the benefit
of rest and resupply at nearby ports on its route.



I think that by current technology, an ideal time would be an around 3
months voyage.

Around 1 month travelling to Mars, around 1 month surveying Mars,
around 1 month returning home from Mars.

Much like the current ISS mission which usually last around 3 months,
before they extend it to around 6 months.

A 6 months mission seems to be pushing it (like they did today),
especially a 1 year mission (like that poor guy that once stuck aboard
Mir).



And if sending an all in one package ship is too hard.

How about sending regular shipments of supplies and parts to the
manned ship? Both before and even after the manned ship was launched.

Making the Mars mission feels more like the current ISS mission. This
will take many launches, but it will be less stressful toward the crew
(which need to do many things and travel farther than the current
space station crew).

(EAC) wrote in
m:

We should compare this to sea ships in the 19th century regular ships
usually takes around 6 months from Hong Kong to New York, while fast
clipper ships usually took around 3 months from one destination to
another destination.

No, we should compare it to the 16th century voyages of Magellan and the
like. Those voyages took years.

I think that by current technology, an ideal time would be an around 3
months voyage.

Had 16th-century Europeans felt as you do, long ocean voyages would have
had to await the development of faster ships such as the clippers. But
without the earlier voyages, there would have been no rational economic
reason to develop faster ships. Those ships were developed to service
markets that had been opened centuries earlier, by slower ships.

You have to start somewhere.
--
JRF

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