Running multiple HET in parallel?

"John Schilling" wrote in message
...
"Carey Sublette" writes:

"John Schilling" wrote in message
...
"Allen Thomson" writes:

However, the viewgraph that started this seemed to say that
the state of the art isn't here for preserving nutritionally
adequate food for multi-year Mars missions. So is there some
ingredient of a multi-year nutritionally complete diet that
can't be preserved by chilling or freezing or dehydration or
whatever? If so, what might it be?

Don't know; I can't find the original references at my local
library or online, just abstracts and summaries. What I can
find suggests it isn't anything as simple as a missing vitamin
or amino acid or whatnot. But in the course of developing the
MRE, the Army did *something* to the mix that resulted in a
food that would last indefinitely if kept cold, but will lead
to unexplained weight loss and mental deterioration if used
exclusively for more than a few weeks.

I think the "cherry box" on the viewgraph:
" Improvements in food storage technology or production technology are
also
needed to reduce overall mass and ensure crew health."
states the issue accurate, but the other sentence on the slide:
"Current food preservation technology is not capable of providing
nutritionally viable food for the longer mission durations under study"
is a bit of a misstatement.

Ensuring crew health requires a diet that is varied and palatable so that
the crew eats properly, and the food itself is not a source of stress on
the
mission (psychological health).

And the trick is to do it with low mass foods (i.e. dehydrated).

Also, nutrition science is far beyond the RDA stage - finding the
essential
individual components in a diet required for health.

Right, and the failures of known long-term stored-food diets are not at
the RDA, individual-componet level either.


I think it is the combined problem of satisfying all of these together,
and
quite clearly no one has ever developed a food system like this before.

The whole viewgraph presentation is about design trade-offs, and the
dietary
aspect of a mission is going to involve trade-offs of its own. For a
palatable, optimally healthy, indefinitely storable diet a solution is at
hand right now - just prepare thousands of excellent meals and freeze them
in ready-to-eat form. But this is quite heavy with all that water.

It's not that easy, alas. Not all foods retain everything that used to
make them nutritious and palatable through a freeze/thaw cycle, at least
using known freezing and thawing processes, and I'm not aware of any
successful attempt at providing a healthy long-term diet using only those
foods known to freeze well.

With modern freezing technology there are very few foods that cannot be
frozen effectively. At worst the penalty is loss of texture, not nutrition,
and texture loss can be compensated by food preparation technique (e.g.
tomatoes become mushy when forzen, but any dish that cooks tomatoes loses
the texture anyway).

Maintaining the good qualities of those meals but getting rid of the water
mass, not so easy.

Getting rid of most of the water would be a plus, but *all* of the known
preservation methods - freezing, canning, dehydrating, and the rest - have
limits. The early arctic and antarctic expeditions were not seriously
mass-limited, at least for their base camps, and certainly did not lack
for refrigeration.

Ahem - no.

Early arctic and antarctic expeditions did *not* have access to "frozen
food"! Frozen foods, in the sense we are discussing, are not just foods that
happen to be frozen. They are foods that preserved intact by a process of
rapid freezing at very low temperatures, and kept frozen continuously by
maintaing temperatures of below -18 C. This means having the food frozen in
a plant at the peak of edibility, and maintained at very cold temperatures
through active refigeration continuously from that moment on. Early
expeditions to the arctic did not have access to such.

The break-through Birdseye process was developed in the 1920s, and frozen
foods only came available in 1930. Only expeditions substantially later than
this could have had adequate support to supply them with properly frozen
foods.

They could and did carry their choice of canned and
frozen food, all fully hydrated, and yet found that a full overwinter
stay was testing the limits of endurance on such a diet.

What do you mean limits of endurance? If you are talking about palatable
diet, this is the same issue I brought up as the principal real problem.

Again, I don't think this is likely to be a major problem. We know more
about food preservation than we did in the early 20th century, and we
know from their experience what doesn't work and what the problems are.
But we also know more about transport logistics than we did in the early
20th century, and have used that to ensure that we never had to test our
presumed ability to have people live for years without any resupply.

That's something we are going to have to test before we sent people to
Mars with an assortment of canned, frozen, and dehydrated food. Tweaking
the diet to increase the fraction of dehydrated food is a secondary goal.

I think the mass problem of the food supply is a bigger issue (in the minds
of NASA at least) than you are allowing.

John Schilling wrote:

[...]
It's not that easy, alas. Not all foods retain everything that used to
make them nutritious and palatable through a freeze/thaw cycle, at least
using known freezing and thawing processes, and I'm not aware of any
successful attempt at providing a healthy long-term diet using only those
foods known to freeze well.

Vitamins in particular tend to degrade, although some of these can be
stored for a couple years in tablet form. 1-A-Day Brand might not be a
good choice -- the pill might end up too big to swallow ;-)


Maintaining the good qualities of those meals but getting rid of the
water mass, not so easy.

Getting rid of most of the water would be a plus, but *all* of the known
preservation methods - freezing, canning, dehydrating, and the rest -
have limits.

Didn't Henry point out that you're going to need the water anyway*?
What's the difference between carrying it in the freezer and carrying it
in the tank? The value of dehyrdated foods is in "instant meals" (or
snacks), such as cups of soup or noodles, and in suitpacks for short trips
away from base camp.

*water for reconstitution, of course, and also for making ou for ELCSS
losses.

/dps

--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

D Schneider wrote:
John Schilling wrote:

[...]
It's not that easy, alas. Not all foods retain everything that used to
make them nutritious and palatable through a freeze/thaw cycle, at least
using known freezing and thawing processes, and I'm not aware of any
successful attempt at providing a healthy long-term diet using only those
foods known to freeze well.
snip
Getting rid of most of the water would be a plus, but *all* of the known
preservation methods - freezing, canning, dehydrating, and the rest -
have limits.

Didn't Henry point out that you're going to need the water anyway*?
What's the difference between carrying it in the freezer and carrying it
in the tank? The value of dehyrdated foods is in "instant meals" (or
snacks), such as cups of soup or noodles, and in suitpacks for short trips
away from base camp.

*water for reconstitution, of course, and also for making ou for ELCSS
losses.

Using relatively easy processes, you can greatly reduce water use.
For example, boiled treated dehumidifier water is quite usable, and that
needs little more than I have in this room. (dehumidifier, UVC lamp. ...)

If you're willing to recycle urine too, which is more tricky to filter and
process, then you're getting pretty close to not actually needing makeup
water, but being able to do fine on water from oxygen burnt with food in the
crew.

There are a number of interesting possible ways to recycle almost
everything pretty cleanly.
Heat excrement/urine/waste food/... to 500C or so in a suitable reaction
vessel under pressure, in presence of water, and you practically get out
after a little while water with assorted ions in, and no larger components.

"Carey Sublette" wrote:

With modern freezing technology there are very few
foods that cannot be frozen effectively.

So long as you define 'effectively' to exclude texture, taste, and
visual appeal.

At worst the penalty is loss of texture, not nutrition,
and texture loss can be compensated by food preparation
technique (e.g. tomatoes become mushy when forzen, but
any dish that cooks tomatoes loses the texture anyway).

Umm.. No. The problems are far more extensive than that, and only
about half of them can be cured by changing the preparation technique.

Pick up a copy of the Ball Blue Book and/or drop rec.food.preserving
and educate yourself.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

"D Schneider" writes:

John Schilling wrote:

Getting rid of most of the water would be a plus, but *all* of the known
preservation methods - freezing, canning, dehydrating, and the rest -
have limits.

Didn't Henry point out that you're going to need the water anyway*?
What's the difference between carrying it in the freezer and carrying it
in the tank?

No. The water that you need is the water that is *chemically* incorporated
into food. Absolutely, positively, completely, 100.0% dehydrated food
has a chemical formula of rounghly CnH2nOn, plus traces of other stuff,
and if you divide by n and oxidize the C, which is roughly what human
metabolism does, you get H2O. A little more than a cupful a day, but
that's a cupful that's being added to your otherwise mostly closed system.
If your recycling is good enough, that should be all you need.

Crudely speaking, if you eat fully dehydrated food and drink, say,
eight cups of water a day, you'll ****, sweat, and exhale nine cups of
water a day. All you have to do is not lose more than a cup a day in
the recycler, and you're set.


--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
* for success" *
*661-718-0955 or 661-275-6795 * -58th Rule of Acquisition *

"D Schneider" wrote in message
newspsnz5yjddemtzlb@d3h1pn11...
...
Getting rid of most of the water would be a plus, but *all* of the known
preservation methods - freezing, canning, dehydrating, and the rest -
have limits.

Didn't Henry point out that you're going to need the water anyway*?
What's the difference between carrying it in the freezer and carrying it
in the tank? The value of dehyrdated foods is in "instant meals" (or
snacks), such as cups of soup or noodles, and in suitpacks for short trips
away from base camp.

*water for reconstitution, of course, and also for making ou for ELCSS
losses.

Ah, but the water for reconstitution can be used over and over and over
(reclaimed from waste and air of course).

Some water in frozen food may actually be needed in the course of the
mission to make for losses or for expendible purposes, in which case it can
be subtracted from the food mass budget.

Lets pencil this out. For a long duration mission (1000 days) with a crew of
8, we have 8000 days of food. A diet is typical 75% water or so, food is
principally carbohydrate and protein containing 4 kilocalories per gram, and
at a 2000 kilocalorie a day diet we have 500g solids, and 1500g water per
person per day. Thus the minimum dry food mass is 4000 kg, with 12000 kg of
water needed. This is really not too bad - I can't imagine it a
make-or-break issue for a Mars mission. On the other hand the entire mass of
the mission vehicle would be on the order of 200 tonnes, so the food water
mass is 6% of the total mission mass. You know they will apply a rigorous
mass budgeting discipline to keep the mission mass down, so the food water
mass is one area they will want to attack. (The NASA PowerPoint presentation
mentioned this specifically.)

BTW - regarding the issue of the nutritive value of frozen foods - there are
no nutrients - essential or otherwise - lost during freezing and thawing.
The only property lost in the food is texture for some types of high-water
foods - principally tomatoes, whole egg, and certain soft fruits (and there
are ways of still incorporating all of these effectively in the diet). Its a
bit harder for dehydrated foods though. (I consulted with my resident food
science graduate-professional on this.)

Carey Sublette

Derek Lyons wrote:
"Carey Sublette" wrote:

With modern freezing technology there are very few
foods that cannot be frozen effectively.

So long as you define 'effectively' to exclude texture, taste, and
visual appeal.

Millions live on frozen meals, chocolate bars, and fizzy drinks.

If the price of going into space is eating slightly boring food, with much
better nutrition than stuff I might pick off the the supermarket shelf, then
I'm willing to make the supreme sacrifice.

I suspect I'm not alone.

"Derek Lyons" wrote in message
...
"Carey Sublette" wrote:

With modern freezing technology there are very few
foods that cannot be frozen effectively.

So long as you define 'effectively' to exclude texture, taste, and
visual appeal.

At worst the penalty is loss of texture, not nutrition,
and texture loss can be compensated by food preparation
technique (e.g. tomatoes become mushy when forzen, but
any dish that cooks tomatoes loses the texture anyway).

Umm.. No. The problems are far more extensive than that, and only
about half of them can be cured by changing the preparation technique.

Pick up a copy of the Ball Blue Book and/or drop rec.food.preserving
and educate yourself.

Umm... are you aware of the differences between state-of-the-art flash
freezing technology and home canning?

Evidently not.

Educate yourself.

Carey Sublette

"Ian Stirling" wrote in message
...
D Schneider wrote:
John Schilling wrote:

[...]
It's not that easy, alas. Not all foods retain everything that used to
make them nutritious and palatable through a freeze/thaw cycle, at least
using known freezing and thawing processes, and I'm not aware of any
successful attempt at providing a healthy long-term diet using only
those
foods known to freeze well.
snip
Getting rid of most of the water would be a plus, but *all* of the known
preservation methods - freezing, canning, dehydrating, and the rest -
have limits.

Didn't Henry point out that you're going to need the water anyway*?
What's the difference between carrying it in the freezer and carrying it
in the tank? The value of dehyrdated foods is in "instant meals" (or
snacks), such as cups of soup or noodles, and in suitpacks for short
trips
away from base camp.

*water for reconstitution, of course, and also for making ou for ELCSS
losses.

Using relatively easy processes, you can greatly reduce water use.
For example, boiled treated dehumidifier water is quite usable, and that
needs little more than I have in this room. (dehumidifier, UVC lamp. ...)

If you're willing to recycle urine too, which is more tricky to filter and
process, then you're getting pretty close to not actually needing makeup
water, but being able to do fine on water from oxygen burnt with food in
the
crew.

The requirements for water purification a Mars mission are not too
demanding.

The average production rate is on the order of 1/2 liter per hour, with a
total system lifetime production of 10,000 liters. Further the cost of
operating the system can be quite high - $1000/liter would not be problem
for this application. The reclamation/recycling system must be light and not
need much maintenance though.

As a thought experiment, consider water purification by electrolyzing the
water to hydrogen and oxygen, then burning it back to water. This would
satisfy any need for purity I should think. The energy cost for operating
this system would be on the order of 1500 watts, not a problem for a vehicle
of this magnitude.

There are a number of interesting possible ways to recycle almost
everything pretty cleanly.
Heat excrement/urine/waste food/... to 500C or so in a suitable reaction
vessel under pressure, in presence of water, and you practically get out
after a little while water with assorted ions in, and no larger
components.

The solid matter in the waste would be much more difficult to put to use,
and also is much lighter than the water so probably just retaining it in
tanks for shielding would be the best use.

Carey Sublette

"Ian Stirling" wrote in message
...
Derek Lyons wrote:
"Carey Sublette" wrote:

With modern freezing technology there are very few
foods that cannot be frozen effectively.

So long as you define 'effectively' to exclude texture, taste, and
visual appeal.

Millions live on frozen meals, chocolate bars, and fizzy drinks.

If the price of going into space is eating slightly boring food, with much
better nutrition than stuff I might pick off the the supermarket shelf,
then
I'm willing to make the supreme sacrifice.

I suspect I'm not alone.

And it need not be even slightly boring!

There is a very substantial, and growing, frozen gourmet food industry. A
little googling, or a trip to a high-end supermarket, easily turns up an
vast range of products.

Stae-of-the-art commercial super flash freezing (which uses ammonia baths
at -65 C), vacuum sealed pouches, and well-controlled preparation processes
introduces few compromises in texture, taste, or appearance and none in
nutrition. Frozen foods are often better in nutrition and not infrequently
in esthetic qualities compared to "real world" fresh, because shipping,
handling, and storage allow for more deterioration for the "fresh".