With the same frivolity as "Has anyone ever built a dalek", I wonder
if any of you have thought about making liquid nitrogen at home.

I always liked cryogenics as a kid :-)

Of course anything is possible - it's just a matter of cost! :-)

M

Markus Splenius wrote:
With the same frivolity as "Has anyone ever built a dalek", I wonder
if any of you have thought about making liquid nitrogen at home.

I always liked cryogenics as a kid :-)

Of course anything is possible - it's just a matter of cost! :-)


It's very, very difficult to do on any kind of DIY budget :-)

However, the good news is it's very easy to buy, and quite cheap too.
You'll need a reasonable sized dewar, maybe 20-25l, and an account with
BOC. I pay ~£40 per fillup.


--
Grunff

Grunff wrote:
Markus Splenius wrote:
With the same frivolity as "Has anyone ever built a dalek", I wonder
if any of you have thought about making liquid nitrogen at home.
I always liked cryogenics as a kid :-)
Of course anything is possible - it's just a matter of cost! :-)


It's very, very difficult to do on any kind of DIY budget :-)

However, the good news is it's very easy to buy, and quite cheap too.
You'll need a reasonable sized dewar, maybe 20-25l, and an account with
BOC. I pay ~£40 per fillup.


Or in a farming area, talk to the local AI man.
(And no, I don't mean Artificial Intelligence.)

--
Ian White
Abingdon, England

On Fri, 07 Jan 2005 15:42:35 +0000, Grunff wrote:

Markus Splenius wrote:
With the same frivolity as "Has anyone ever built a dalek", I wonder
if any of you have thought about making liquid nitrogen at home.

I always liked cryogenics as a kid :-)

Of course anything is possible - it's just a matter of cost! :-)


It's very, very difficult to do on any kind of DIY budget :-)

However, the good news is it's very easy to buy, and quite cheap too.
You'll need a reasonable sized dewar, maybe 20-25l, and an account with
BOC. I pay ~£40 per fillup.

And what do you use it for Grunff? Surely not just for party tricks?
:-)

M.

Markus Splenius wrote:

And what do you use it for Grunff? Surely not just for party tricks?
:-)

Sadly it is just for messing around. I have a nitrogen laser which I run
off it sometimes, but that's about the most useful thing I do with it!

What happened was I missed it too much after my time in the lab, so had
to sort out a private supply.

--
Grunff

Grunff wrote:
Markus Splenius wrote:
With the same frivolity as "Has anyone ever built a dalek", I wonder
if any of you have thought about making liquid nitrogen at home.

I always liked cryogenics as a kid :-)

Of course anything is possible - it's just a matter of cost! :-)


It's very, very difficult to do on any kind of DIY budget :-)

However, the good news is it's very easy to buy, and quite cheap too.
You'll need a reasonable sized dewar, maybe 20-25l, and an account with
BOC. I pay ~?40 per fillup.

What sort of requirements are there on getting an account?
How much is a dewar?

Hydrogen peroxide vacuum distillation to make HTP for rockets is annoying,
and I was wondering if O2 might be more usable.

(messing around in garage making rockets - eventual goal is a 4 stage orbital
one with a kilo to orbit.)

Ian Stirling wrote:

What sort of requirements are there on getting an account?

This varies a lot depending on who you talk to. There is supposed to be
a minimum annual spend, but I've never had this enforced. I buy 2-3
loads a year.


How much is a dewar?

New a 25l dewar is about £300, but you can get second hand ones for
around £100.


Hydrogen peroxide vacuum distillation to make HTP for rockets is annoying,
and I was wondering if O2 might be more usable.

Liquid O2 is a lot less readily available, but you can still get it if
you try.


(messing around in garage making rockets - eventual goal is a 4 stage orbital
one with a kilo to orbit.)

Excellent!


--
Grunff

"Markus Splenius" wrote in message
...
On Fri, 07 Jan 2005 15:42:35 +0000, Grunff wrote:

Markus Splenius wrote:
With the same frivolity as "Has anyone ever built a dalek", I wonder
if any of you have thought about making liquid nitrogen at home.

I always liked cryogenics as a kid :-)

Of course anything is possible - it's just a matter of cost! :-)


It's very, very difficult to do on any kind of DIY budget :-)

However, the good news is it's very easy to buy, and quite cheap too.
You'll need a reasonable sized dewar, maybe 20-25l, and an account with
BOC. I pay ~£40 per fillup.

And what do you use it for Grunff? Surely not just for party tricks?
:-)


Ice cream, of course!

I'm half-seriously thinking about doing it as a finale for one of our
barbeques this summer.


--
Richard Sampson

mail me at
richard at olifant d-ot co do-t uk

Tony Bryer wrote:

I remember going to a Royal Institution (?) science lecture
whilst at school and the lecturer put a sausage in a flask of
liquid gas. When he took it out it was of course supercold: he
dropped it and it shattered into fragments. Ever since I've
wondered what those fragments would be when thawed out: a sort
of mince? I'm not asking you to repeat the experiment g


Small, squishy lumps of sausage meat.

One great thing you can use it for is freezing herbs. I haven't done
this in years (been too busy with house project), but the quick freezing
really preserves the flavour.


--
Grunff

In article , "Tony Bryer"
says...
In article , Grunff wrote:
However, the good news is it's very easy to buy, and quite
cheap too. You'll need a reasonable sized dewar, maybe 20-25l,
and an account with BOC. I pay ~£40 per fillup.

I remember going to a Royal Institution (?) science lecture
whilst at school and the lecturer put a sausage in a flask of
liquid gas. When he took it out it was of course supercold: he
dropped it and it shattered into fragments. Ever since I've
wondered what those fragments would be when thawed out: a sort
of mince? I'm not asking you to repeat the experiment g

I saw a similar thing at the Smithsonian, only he used a squash ball
and chucked it pretty high. When it hit the floor some unsuspecting
passers-by had a bit of a shock - it made quite a bang and there was
shrapnel flying around. Afterwards I picked up a few pieces; the
fractured surfaces looked like broken glass.

Andrew Chesters wrote:
Grunff wrote:
Ian Stirling wrote:

What sort of requirements are there on getting an account?


This varies a lot depending on who you talk to. There is supposed to be
a minimum annual spend, but I've never had this enforced. I buy 2-3
loads a year.

Thanks.
How much is a dewar?

New a 25l dewar is about ?300, but you can get second hand ones for
around ?100.


Hydrogen peroxide vacuum distillation to make HTP for rockets is
annoying,
and I was wondering if O2 might be more usable.


Liquid O2 is a lot less readily available, but you can still get it if
you try.

HTP H2O2 is even less available.
IIRC, 70-90% may be available if you're willing to buy a train load, but
otherwise you've pretty much got to distill it yourself.

(messing around in garage making rockets - eventual goal is a 4 stage
orbital
one with a kilo to orbit.)

Excellent!

Agree with the "Excellent"; but I somehow hope I live up-range from Ian!!

Well, I can always get you on reentry

Actually, the stage weights are fairly modest, somewhere around 5Kg, 25Kg,
125Kg, 625Kg (fueled), so on launch it's well under a ton.
And the first stage is meant to come back on a parasail.

The second stage, which bits may reenter intact of, has a dry weight of
only 25Kg.

I was initially considering a launch from around John-o-groats (sp?) over
the pole.

On Fri, 07 Jan 2005 15:42:35 +0000, Grunff wrote:

Markus Splenius wrote:
With the same frivolity as "Has anyone ever built a dalek", I wonder
if any of you have thought about making liquid nitrogen at home.

I always liked cryogenics as a kid :-)

Of course anything is possible - it's just a matter of cost! :-)


It's very, very difficult to do on any kind of DIY budget :-)

I would think you would need at least a scuba bottle compressor.
You then need a longish length of very very small gauge metal tube
(probably less than 0.5mm ID). This you coil so it fits into a very
very small thermos flask.

The output of the scuba receiver (already cooled to ambient) compressed at
about 200 bar goes into the fine tube the air escaping from the open end
of the is cool this pre-cools the compressed air coming down the fine tube
until the stuff coming out is so cold it's liquid.

I've done this at college with a 200 bar bottle of nitrogen as the source.
This made about a thimble full in 5 minutes. The flask part being the size
of a thimble so it might only work on that scale. 8-(

I expect there are some nasty gotchas like having to get rid of all the
water and CO2 from the air before compression? 8-(

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

"Ian Stirling" wrote in message
...
Grunff wrote:
Markus Splenius wrote:
With the same frivolity as "Has anyone ever built a dalek", I wonder
if any of you have thought about making liquid nitrogen at home.

Hydrogen peroxide vacuum distillation to make HTP for rockets is annoying,
and I was wondering if O2 might be more usable.

(messing around in garage making rockets - eventual goal is a 4 stage
orbital
one with a kilo to orbit.)

Why 4 stage ? I've always thought the helium weather balloon (also from
BOC) then a single stage (fired in the correct direction and not through the
balloon aka "the difficult bit") was the most elegant approach. (this is
about to go sooooo OT)

On Fri, 07 Jan 2005 15:42:35 +0000, Grunff wrote:

It's very, very difficult to do on any kind of DIY budget :-)

No, many people have built LN2 refrigerators. It's hard to do it
efficiently, but refrigeration to this temperature isn't much harder
than making your own gas turbine.

Don't forget that Ohnes liquified helium in 1911 and discovered
superconductivity almost immediately afterwards. Nitrogen was back in
the 1880's. Now how much technology did any lab have back then that
you can't reproduce in a half-decent modern home workshop ?

--
Smert' spamionam

On Fri, 07 Jan 2005 16:42:15 +0000, Grunff wrote:

New a 25l dewar is about £300, but you can get second hand ones for
around £100.

Even more fun - damaged Dewars are free and the TIG welding course is
about £200. If it's not aluminium and the damage is minor, you might
just be able to silver solder it.

"Andy Dingley" wrote in message
...
On Fri, 07 Jan 2005 15:42:35 +0000, Grunff wrote:

It's very, very difficult to do on any kind of DIY budget :-)

No, many people have built LN2 refrigerators. It's hard to do it
efficiently, but refrigeration to this temperature isn't much harder
than making your own gas turbine.

Don't forget that Ohnes liquified helium in 1911 and discovered
superconductivity almost immediately afterwards. Nitrogen was back in
the 1880's. Now how much technology did any lab have back then that
you can't reproduce in a half-decent modern home workshop ?

Well the availability of whatever ore the Curies purified radium from is
presumably a little harder to get now :-)

"Ian Stirling" wrote in message
...
Andrew Chesters wrote:
Grunff wrote:
Ian Stirling wrote:

What sort of requirements are there on getting an account?


This varies a lot depending on who you talk to. There is supposed to be
a minimum annual spend, but I've never had this enforced. I buy 2-3
loads a year.

Thanks.
How much is a dewar?

New a 25l dewar is about ?300, but you can get second hand ones for
around ?100.


Hydrogen peroxide vacuum distillation to make HTP for rockets is
annoying,
and I was wondering if O2 might be more usable.


Liquid O2 is a lot less readily available, but you can still get it if
you try.

HTP H2O2 is even less available.
IIRC, 70-90% may be available if you're willing to buy a train load, but
otherwise you've pretty much got to distill it yourself.

(messing around in garage making rockets - eventual goal is a 4 stage
orbital
one with a kilo to orbit.)

Excellent!

Agree with the "Excellent"; but I somehow hope I live up-range from
Ian!!

Well, I can always get you on reentry

Actually, the stage weights are fairly modest, somewhere around 5Kg, 25Kg,
125Kg, 625Kg (fueled), so on launch it's well under a ton.
And the first stage is meant to come back on a parasail.

The second stage, which bits may reenter intact of, has a dry weight of
only 25Kg.

I was initially considering a launch from around John-o-groats (sp?) over
the pole.

That'll cost you in orbital velocity: you won't pick up anything from the
earth's rotation in that direction. I assume you've done the calculations
:-). I've been down to the ESA launch site at Kourou, French Guiana, and
it's there for a good reason, unobstructed launch path east over the
atlantic and only 5 degrees north. You'd better talk to the folks in the
Orkneys, they're due north of John O'Groats!

Andy.

andrewpreece wrote:

"Ian Stirling" wrote in message
...
Andrew Chesters wrote:
Grunff wrote:
Ian Stirling wrote:

What sort of requirements are there on getting an account?


This varies a lot depending on who you talk to. There is supposed to be
a minimum annual spend, but I've never had this enforced. I buy 2-3
loads a year.

Thanks.
How much is a dewar?

New a 25l dewar is about ?300, but you can get second hand ones for
around ?100.


Hydrogen peroxide vacuum distillation to make HTP for rockets is
annoying,
and I was wondering if O2 might be more usable.

Liquid O2 is a lot less readily available, but you can still get it if
you try.

snip
I was initially considering a launch from around John-o-groats (sp?) over
the pole.

That'll cost you in orbital velocity: you won't pick up anything from the
earth's rotation in that direction. I assume you've done the calculations
:-). I've been down to the ESA launch site at Kourou, French Guiana, and
it's there for a good reason, unobstructed launch path east over the
atlantic and only 5 degrees north. You'd better talk to the folks in the
Orkneys, they're due north of John O'Groats!

Not quite due north.
I'm budgeting for a very, very large contingancy delta-v, around a
kilometer a second, just in case.
Part of the design is to be able to cope with unexpected stage
underperformance, or the flame going out.

Fuel is cheap.

"Mike" wrote
| Well the availability of whatever ore the Curies purified radium
| from is presumably a little harder to get now :-)

And can you imagine the expression on a buyer's face when you answered "no,
there's no asbestos in the house, but we did do some radiology experiments
in the scullery"

Owain

On Fri, 7 Jan 2005 20:49:46 -0000, "Mike" wrote:

Well the availability of whatever ore the Curies purified radium from is
presumably a little harder to get now :-)

No idea - the usual "ores" for the back-bedroom Teller-wannabees these
days are that old favourite, thorium from caravan gas mantles, or else
americium from smoke detectors.

The Curies went through _tons_ of pitchblende. We just don't have the
space to do it these days.

--
Smert' spamionam

No idea - the usual "ores" for the back-bedroom Teller-wannabees these
days are that old favourite, thorium from caravan gas mantles,

I think most, maybe all, don't have it anymore.

Damn them and their ways to constantly foil my evil plans!!!

Sam

"Ian Stirling" wrote in message
...
andrewpreece wrote:

"Ian Stirling" wrote in message
...
Andrew Chesters wrote:
Grunff wrote:
Ian Stirling wrote:

What sort of requirements are there on getting an account?


This varies a lot depending on who you talk to. There is supposed to
be
a minimum annual spend, but I've never had this enforced. I buy 2-3
loads a year.

Thanks.
How much is a dewar?

New a 25l dewar is about ?300, but you can get second hand ones for
around ?100.


Hydrogen peroxide vacuum distillation to make HTP for rockets is
annoying,
and I was wondering if O2 might be more usable.

Liquid O2 is a lot less readily available, but you can still get it
if
you try.

snip
I was initially considering a launch from around John-o-groats (sp?)
over
the pole.

That'll cost you in orbital velocity: you won't pick up anything from
the
earth's rotation in that direction. I assume you've done the
calculations
:-). I've been down to the ESA launch site at Kourou, French Guiana, and
it's there for a good reason, unobstructed launch path east over the
atlantic and only 5 degrees north. You'd better talk to the folks in the
Orkneys, they're due north of John O'Groats!

Not quite due north.
I'm budgeting for a very, very large contingancy delta-v, around a
kilometer a second, just in case.
Part of the design is to be able to cope with unexpected stage
underperformance, or the flame going out.

Fuel is cheap.

Fascinating: I thought at first you were making it up! AFAIK noone has done
anything like this, the X-prize contestants aren't anywhere near orbital
velocity and the performance needed in terms of fuel goes up as the square
of the velocity, and you reckon you've a km/sec delta-v as contingency! I am
all admiration Sir! I've seen other rocket groups' websites ( one group is
called MARS ) but none are quite as ambitious. The amount of human effort
needed to achieve the kind of performance you specify is considerable. Any
chance of a technical overview or is it all under wraps?

Andy.

"andrewpreece" wrote in message
...
! AFAIK noone has done
anything like this, the X-prize contestants aren't anywhere near orbital
velocity

Aren't they ? I thought the prize had been won. Don't they actually have
to achieve orbit to win ?

Mike wrote:

Aren't they ? I thought the prize had been won. Don't they actually have
to achieve orbit to win ?

No just a specific height, 100km IIRC, their trajectory was something
like this ...

^
/ \
| |
| |
| |
| |
/ |
/ \
-/ \-

Wouldn't "orbital velocity" vary depending on the height you wished to
orbit at? Perhaps someone was thinking of "escape velocity" which is
about 26,000mph

"Andy Burns" wrote in message
...
Mike wrote:

Aren't they ? I thought the prize had been won. Don't they actually
have
to achieve orbit to win ?

No just a specific height, 100km IIRC, their trajectory was something
like this ...

^
/ \
| |
| |
| |
| |
/ |
/ \
-/ \-

Wouldn't "orbital velocity" vary depending on the height you wished to
orbit at?

Whay does the shuttle and Spacelab need ? That sounds a good start.


Perhaps someone was thinking of "escape velocity" which is
about 26,000mph

So this Virgin "spaceplane" they're building won't even get you near a
proper orbit then ? Does it reach the point where you feel weightless
(other than when it goes into a controlled dive) ?

Andy Dingley wrote:

Don't forget that Ohnes liquified helium in 1911 and discovered
superconductivity almost immediately afterwards. Nitrogen was back in
the 1880's. Now how much technology did any lab have back then that
you can't reproduce in a half-decent modern home workshop ?


This is a fair point, but it would be quite a bit of work none the less.
Got any diagrams etc. of homebuilt kit?


--
Grunff

Mike wrote:

Whay does the shuttle and Spacelab need ? That sounds a good start.

Apparently the ISS is currently 349km high and whizzing over Egypt
http://science.nasa.gov/temp/StationLoc.html

Some nice formulae for calulating orbital speeds for a given altitude
http://www.aerospaceweb.org/question...ft/q0164.shtml
for 300km it would be 17000mph

So this Virgin "spaceplane" they're building won't even get you near a
proper orbit then ? Does it reach the point where you feel weightless
(other than when it goes into a controlled dive) ?

From what I heard the Virgin/SpaceShipTwo will go higher than the
SpaceShipOne, and you will get several minutes of weighlessness for your
$200,000

In article ,
Grunff writes:
Andy Dingley wrote:

Don't forget that Ohnes liquified helium in 1911 and discovered
superconductivity almost immediately afterwards. Nitrogen was back in
the 1880's. Now how much technology did any lab have back then that
you can't reproduce in a half-decent modern home workshop ?

This is a fair point, but it would be quite a bit of work none the less.
Got any diagrams etc. of homebuilt kit?

ISTR it can be done with a compressor and pair of concentric
copper pipes. These are coiled up and inserted into a thermos or
dewer. Air is pumped down the central one which has an expansion
jet on the end which cools the air. The cool air is recovered
back up the outside one which further cools the air coming down
the central one, until eventually the air gets cold enough to
start liquifying when it leaves the expansion jet. At least,
this is my recollection of one way of doing it from O-level
physics.

There appear to be some details missing from this, like where
the heat gets dumped. Probably, the compressed air is cooled
back down to room temperature before it enters the coil to be
further cooled by the returning air. (It is not necessary to
send the same air round and round the system.)

Obviously, starting with air, you end up with liquified air
rather than nitrogen. The boiling points of nitrogen, oxygen
and argon are near enough you'll get them all ISTR.

This subject came up a few months back, as I was considering
trying to do this with a compressor from a freezer. I did
google around thinking there was probably a secret society of
low temperature hobbists out there doing this, but came up with
nothing, so if there is, they are very secret. I couldn't even
find a description of the process above which I recall from my
O-level physics lessons.

--
Andrew Gabriel

"Markus Splenius" wrote in message


However, the good news is it's very easy to buy, and quite cheap too.
You'll need a reasonable sized dewar, maybe 20-25l, and an account with
BOC. I pay ~£40 per fillup.

And what do you use it for Grunff? Surely not just for party tricks?

It was to give him the reputation of a hard man but his wife found him
rather cold so she broke it off.

Apparently they all give him the cold shoulder these days.

So be careful!



--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

andrewpreece wrote:

"Ian Stirling" wrote in message
snip
I'm budgeting for a very, very large contingancy delta-v, around a
kilometer a second, just in case.
Part of the design is to be able to cope with unexpected stage
underperformance, or the flame going out.

Fuel is cheap.

Fascinating: I thought at first you were making it up! AFAIK noone has done
anything like this, the X-prize contestants aren't anywhere near orbital
velocity and the performance needed in terms of fuel goes up as the square
of the velocity, and you reckon you've a km/sec delta-v as contingency! I am
all admiration Sir! I've seen other rocket groups' websites ( one group is
called MARS ) but none are quite as ambitious. The amount of human effort
needed to achieve the kind of performance you specify is considerable. Any
chance of a technical overview or is it all under wraps?

At the moment I'm working on ancillery systems, guidance and stuff, and
working out best ways of making cheap small regeneratively cooled rocket
engines.

In a way, it's not very ambitious.
Some groups are going for things like single stage or 2 stage to orbit.

This means that you almost have to go to extreme lengths to reduce the
weight of the vehicle, and are very highly penalised by small size due to
having to push through the atmosphere.
(adding a percent to the dry mass of a 1 or 2 stage vehicle can often be the
difference between having a payload, and not being able to reach orbit empty.

If you're willing to go with more stages, then in some ways things get
easier.
You throw away empty tanks along the way, which means that you don't have
to have one big very light tank.

You reduce the total mass you have to take to orbit, as the size of rocket
engine on the upper stages is smaller, hence lighter, so you don't have to
worry so much about the takeoff engines weight, or make it so that it can be
throttled down so far, and in some cases can eliminate the need for the
engine to be restartable.

All of this is good, as it makes the hard bits (rocket engine, ...) a little
easier, and means that instead of needing Aluminium-Lithium tanks, you can
go with not very good steel or fiberglass, can use screwfix 2.99 full-bore
ball valves instead of machining something exotic and light, ...

Yes, it may use 25 times more fuel than a 'good' rocket, but fuel is cheap.

(I'm aiming for a cost for the whole thing of only 10K )

This is for around a kilo to LEO.
For much more, this approach starts to break down, and you need to go to
appropriate high technology in some parts in order to keep costs down.
It doesn't make sense to (for example) make a much larger rocket out of
simple to construct steel, if the overall cost is lower with better
harder to weld steel.

Or in a farming area, talk to the local AI man. (And no, I don't mean
Artificial Intelligence.)

I thought most of that was on these news groups g

Dave

--

Some people use windows, others have a life.

Dave Stanton wrote:

Or in a farming area, talk to the local AI man. (And no, I don't mean
Artificial Intelligence.)

I thought most of that was on these news groups g


One of the best things about this ng is that it has plenty of the real
stuff (and this time I *do* mean Intelligence)


--
Ian White
Abingdon, England

"Andy Burns" wrote in message
...
Mike wrote:

Whay does the shuttle and Spacelab need ? That sounds a good start.

Apparently the ISS is currently 349km high and whizzing over Egypt
http://science.nasa.gov/temp/StationLoc.html

Some nice formulae for calulating orbital speeds for a given altitude
http://www.aerospaceweb.org/question...ft/q0164.shtml
for 300km it would be 17000mph

So this Virgin "spaceplane" they're building won't even get you near a
proper orbit then ? Does it reach the point where you feel weightless
(other than when it goes into a controlled dive) ?

From what I heard the Virgin/SpaceShipTwo will go higher than the
SpaceShipOne, and you will get several minutes of weighlessness for your
$200,000

Is that real weightlessness or the same as you can get in one of those
Russian transport planes for $5k ?

"Andrew Gabriel" wrote in message
...
In article ,
Grunff writes:
Andy Dingley wrote:

Don't forget that Ohnes liquified helium in 1911 and discovered
superconductivity almost immediately afterwards. Nitrogen was back in
the 1880's. Now how much technology did any lab have back then that
you can't reproduce in a half-decent modern home workshop ?

This is a fair point, but it would be quite a bit of work none the less.
Got any diagrams etc. of homebuilt kit?

ISTR it can be done with a compressor and pair of concentric
copper pipes. These are coiled up and inserted into a thermos or
dewer. Air is pumped down the central one which has an expansion
jet on the end which cools the air. The cool air is recovered
back up the outside one which further cools the air coming down
the central one, until eventually the air gets cold enough to
start liquifying when it leaves the expansion jet. At least,
this is my recollection of one way of doing it from O-level
physics.

There appear to be some details missing from this, like where
the heat gets dumped. Probably, the compressed air is cooled
back down to room temperature before it enters the coil to be
further cooled by the returning air. (It is not necessary to
send the same air round and round the system.)

Obviously, starting with air, you end up with liquified air
rather than nitrogen. The boiling points of nitrogen, oxygen
and argon are near enough you'll get them all ISTR.

This subject came up a few months back, as I was considering
trying to do this with a compressor from a freezer. I did
google around thinking there was probably a secret society of
low temperature hobbists out there doing this, but came up with
nothing, so if there is, they are very secret. I couldn't even
find a description of the process above which I recall from my
O-level physics lessons.


Don't shout this too loud or we'll have Prescott's mob doing part
whatever's next "Licencing and control of home research laboratories"

Yes, Mr BCO, this is where we attach the brain to the lightning rod. Can I
have yours ?

"Huge" wrote in message
...
"Mike" writes:

"andrewpreece" wrote in message
...
! AFAIK noone has done
anything like this, the X-prize contestants aren't anywhere near
orbital
velocity

Aren't they ? I thought the prize had been won. Don't they actually
have
to achieve orbit to win ?



No. Yes. No.

Is there a prize for real orbit then ?

Ed Sirett wrote:

On Fri, 07 Jan 2005 15:42:35 +0000, Grunff wrote:

Markus Splenius wrote:
With the same frivolity as "Has anyone ever built a dalek", I wonder
if any of you have thought about making liquid nitrogen at home.

I always liked cryogenics as a kid :-)

Of course anything is possible - it's just a matter of cost! :-)


It's very, very difficult to do on any kind of DIY budget :-)

I would think you would need at least a scuba bottle compressor.
You then need a longish length of very very small gauge metal tube
(probably less than 0.5mm ID). This you coil so it fits into a very
very small thermos flask.

The output of the scuba receiver (already cooled to ambient) compressed at
about 200 bar goes into the fine tube the air escaping from the open end
of the is cool this pre-cools the compressed air coming down the fine tube
until the stuff coming out is so cold it's liquid.

I've done this at college with a 200 bar bottle of nitrogen as the source.
This made about a thimble full in 5 minutes. The flask part being the size
of a thimble so it might only work on that scale. 8-(

I expect there are some nasty gotchas like having to get rid of all the
water and CO2 from the air before compression? 8-(

Not really, any water in LN2 freezes so cold it sublimates away. CO2
freezes solid and in some situations can by seen as a frost on the walls
of the Dewar or rolling around on the bottom as nodules.

Peter
--
Add my middle initial to email me. It has become attached to a country

On Sat, 08 Jan 2005 01:45:11 +0000, Andrew Gabriel wrote:

In article ,
Grunff writes:
Andy Dingley wrote:

Don't forget that Ohnes liquified helium in 1911 and discovered
superconductivity almost immediately afterwards. Nitrogen was back in
the 1880's. Now how much technology did any lab have back then that
you can't reproduce in a half-decent modern home workshop ?

This is a fair point, but it would be quite a bit of work none the less.
Got any diagrams etc. of homebuilt kit?

ISTR it can be done with a compressor and pair of concentric
copper pipes. These are coiled up and inserted into a thermos or
dewer. Air is pumped down the central one which has an expansion
jet on the end which cools the air. The cool air is recovered
back up the outside one which further cools the air coming down
the central one, until eventually the air gets cold enough to
start liquifying when it leaves the expansion jet. At least,
this is my recollection of one way of doing it from O-level
physics.

There appear to be some details missing from this, like where
the heat gets dumped. Probably, the compressed air is cooled
back down to room temperature before it enters the coil to be
further cooled by the returning air. (It is not necessary to
send the same air round and round the system.)

Obviously, starting with air, you end up with liquified air
rather than nitrogen. The boiling points of nitrogen, oxygen
and argon are near enough you'll get them all ISTR.

This subject came up a few months back, as I was considering
trying to do this with a compressor from a freezer. I did
google around thinking there was probably a secret society of
low temperature hobbists out there doing this, but came up with
nothing, so if there is, they are very secret. I couldn't even
find a description of the process above which I recall from my
O-level physics lessons.


I don't know if you saw my post.
I'm fairly sure you'll need 200bar for the air.
The heat given off compressing air to that amount is huge.
And needs to be removed before the compressed air enter the low temp part.

I'm fairly sure the fridge kit is only good for a few bar output.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
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