Huygens shortlived?

In sci.space.policy 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).


There is nothing really prohibiting a mission that just gathers data/sleeps
between communication attempts.
You'd need to add several things.
A RHU, to keep it warm enough for the batteries to work.
You'd probably want to add a camera with a zoom lens and a swivel, something
to measure wind-speed (hot-wire anemometer?), in addition to the existing
atmospheric science package.

Prai Jei ) wrote:
: dexx (or somebody else of the same name) wrote thusly in message
: . com:

: 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.

: Did we know how long a day is on Titan?

Titan rotates once every 15.9 days.

Eric


: --
: Paul Townsend
: Pair them off into threes

: Interchange the alphabetic letter groups to reply

Did we know how long a day is on Titan?
--
Titan's is synchronised with it's revolution. 15.95 of our days.

JMB

In article ,
Ian Stirling wrote:
There is nothing really prohibiting a mission that just gathers data/sleeps
between communication attempts.
You'd need to add several things.
A RHU, to keep it warm enough for the batteries to work.

Unfortunately, Huygens already had a whole bunch of RHUs.

The problem with RHUs is that there is no way to switch them off when your
electronics are active and you don't need quite as much heat. Or when
you're closer to the Sun, early in the mission, and need rather less heat.

Even setting that aside, it's rather tricky to set things up so that the
RHUs supply *all* your heat but not too much, especially in an atmosphere
whose detailed thermal characteristics are not well known. (And then
there's the possibility that you might be floating in a liquid...)

In practice, you need some way to *control* the internal temperature.
Much the simplest way to do that, unfortunately, is to have the RHUs
supply only the very smallest amount of heat you might ever want, and make
up the extra with electrical heat. There are more elegant ways of doing
this, but they add complexity and often moving parts, and spacecraft
designers tend to distrust them.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

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

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

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 |