Huygens shortlived?

Is it true that Huygens ceased transmission less than 2 hours after
touchdown? Whilst it was a magnificent achievement to travel so far and
land perfectly, it seems a great shame that the probe was so short
lived. I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

In article . com,
dexx wrote:
Is it true that Huygens ceased transmission less than 2 hours after
touchdown?

Exact numbers aren't on hand, but that's generally right. Bear in mind
that Cassini went below Huygens's horizon around that time, so no further
data relaying was possible anyway.

The primary mission was complete three *minutes* after touchdown. Huygens
was mostly an atmosphere probe; the surface imaging and instruments were
an extra.

...it seems a great shame that the probe was so short
lived. I'm suprised the designers didnt make it rugged enough and
powered enough to survive several days.

It would have greatly increased the cost and complexity, unfortunately,
because it would almost certainly have required an RTG. Moreover, several
days is not enough -- it'll be a month or two (I forget exactly) before
Cassini goes past Titan again. You can't really do a long-lived Titan
surface mission without better communications support, that is, either a
Titan orbiter or a lander that's big enough and heavy enough to carry its
own high-power transmitter and steerable high-gain antenna (plus the power
source needed to run them).
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

Henry Spencer wrote:
[snip]
It would have greatly increased the cost and complexity, unfortunately,
because it would almost certainly have required an RTG. Moreover, several
days is not enough -- it'll be a month or two (I forget exactly) before
Cassini goes past Titan again. You can't really do a long-lived Titan
surface mission without better communications support, that is, either a
Titan orbiter or a lander that's big enough and heavy enough to carry its
own high-power transmitter and steerable high-gain antenna (plus the power
source needed to run them).

To be fair, an RTG powered lander might very well have had
enough power to send data directly back to Earth. At low
bit rate certainly, but probably fast enough to be workable.
Galileo was able to operate at pitiful data rates, with
spectacular results, for example.

However, the surface science capabilities of the probe didn't
justify massive expenditures to increase the return for that
portion of the mission. A new probe with different
instruments and a different design, perhaps, but not Huygens.
Also, I believe that it would have been enormously difficult
to design Huygens and provide a large enough RTG to keep it
operating in the event of a landing in liquid hydrocarbons,
which was, and still is, a substantial possibility for a
Titan lander.

Considering how long ago Huygens was built, and that it was
the first foray into a virtually unknown world, I think it
did spectacularly well. We can do better next time, but
partly that's because of the extraordinarily valuable data
Huygens has provided.

Christopher M. Jones wrote:

Also, I believe that it would have been enormously difficult
to design Huygens and provide a large enough RTG to keep it
operating in the event of a landing in liquid hydrocarbons,
which was, and still is, a substantial possibility for a
Titan lander.

My understanding is Huygens was designed to survive such
a landing and continue to function while floating in
hydrocarbons.

I could be mistaken however.

Steve

Steve Pope wrote:
Christopher M. Jones wrote:
Also, I believe that it would have been enormously difficult
to design Huygens and provide a large enough RTG to keep it
operating in the event of a landing in liquid hydrocarbons,
which was, and still is, a substantial possibility for a
Titan lander.

My understanding is Huygens was designed to survive such
a landing and continue to function while floating in
hydrocarbons.

I could be mistaken however.

I think the better phrasing would be that it was designed
with some thought that they'd like to to survive landing,
and that they were aware that it might land on land or
a liquid ocean, but that it wasn't really a huge design
priority.

If it had landed on very very solid strong material,
it would probably have broken. Same for on a loose
soil, but on top of a big enough rock.

If it landed in a liquid with enough sideways velocity
or tilt, I think it would have tipped over (and then
probably have sunk). It had moderate dynamic stability
afloat in likely liquid sea materials for Titan;
nothing like what you'd want to see for a real long
term surface probe.

They had a tight weight budget and dollar budget,
and did what they could to keep it survivable on
the surface, not knowing what that surface was
going to be.


-george william herbert

George William Herbert wrote:
Steve Pope wrote:
Christopher M. Jones wrote:
Also, I believe that it would have been enormously difficult
to design Huygens and provide a large enough RTG to keep it
operating in the event of a landing in liquid hydrocarbons,
which was, and still is, a substantial possibility for a
Titan lander.

My understanding is Huygens was designed to survive such
a landing and continue to function while floating in
hydrocarbons.

I could be mistaken however.

I think the better phrasing would be that it was designed
with some thought that they'd like to to survive landing,
and that they were aware that it might land on land or
a liquid ocean, but that it wasn't really a huge design
priority.

They planned for the contingecy of a liquid landing. One of the UK
experiments was a densometer for analysing the liquid.

Dave

George William Herbert wrote:

They had a tight weight budget and dollar budget,
and did what they could to keep it survivable on
the surface, not knowing what that surface was
going to be.
Maybe next time they try to aim for an ocean.
Much easier to land on.

Lots of Greetings!
Volker

In article ,
George William Herbert wrote:
If it had landed on very very solid strong material,
it would probably have broken...
If it landed in a liquid with enough sideways velocity
or tilt, I think it would have tipped over...

Add to this: if it had landed intact but tipped up at a substantial tilt,
nothing dire would have happened to it... but Cassini wouldn't have been
able to hear it. The antenna wasn't fully omnidirectional: it put most
of the transmitter output out nearly horizontally.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

Steve Pope wrote:
Christopher M. Jones wrote:


Also, I believe that it would have been enormously difficult
to design Huygens and provide a large enough RTG to keep it
operating in the event of a landing in liquid hydrocarbons,
which was, and still is, a substantial possibility for a
Titan lander.


My understanding is Huygens was designed to survive such
a landing and continue to function while floating in
hydrocarbons.
Yes. For three minutes.

Greetings!
Volker

Steve Pope wrote:
My understanding is Huygens was designed to survive such
a landing and continue to function while floating in
hydrocarbons.

I could be mistaken however.

It was designed to have the maximum possible survival
rate in the event of a landing in liquid that the
designers could give it, within the design constraints.
However, this chance was not much. A pool of liquid
hydrocarbons at near liquid Nitrogen temperatures makes
an awfully efficient coolant. So much so that had
Huygens landed in liquid methane it would have ended
its operational life very quickly thereafter.

The crux of the issue is that Huygens' design is
fundamentally incompatable with long duration, or even
medium duration, surface science, let alone on Titan.
It needs not only greater longevity in general but
also different instruments and different overall design.
I think the inflatable wheeled rover / aerobot* is
probably the best design for this sort of thing available
at the moment. It would use 3 separate Helium filled
balloons as wheels in a rover. These would enable the
craft to operate as an aerobot during and after descent
(it could also take the place of parachutes), which would
permit it to perform extensive surveys of the atmosphere
and surface. Later the balloons can be partially
deflated to approach or touch down on the surface, for
higher resolution imagery or surface science. Finally,
while on the surface the Helium could be replaced with
ambient atmosphere, transforming the vehicle to an
amphibious rover. It looks to be an enormously capable
design, with quite a lot of potential.


(*) http://www.lpi.usra.edu/meetings/out...1/pdf/4023.pdf

http://www2.jpl.nasa.gov/adv_tech/rovers/summary.htm