Former astronaut says it is extremely important to study artificial gravity...

[Jan Panteltje]

Former astronaut says it is \"extremely important\" to study artificial gravity
\"We have nothing in between one and zero.\"
https://arstechnica.com/space/2023/07/former-astronaut-says-its-extremely-important-to-study-artificial-gravity/

I agree with that
maybe even oumuamua rotates to create artificial gravity?

 

[John Larkin]

On Tue, 18 Jul 2023 05:04:58 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

Former astronaut says it is \"extremely important\" to study artificial gravity
\"We have nothing in between one and zero.\"
https://arstechnica.com/space/2023/07/former-astronaut-says-its-extremely-important-to-study-artificial-gravity/

I agree with that
maybe even oumuamua rotates to create artificial gravity?

I love all these high-resolution photographs:

https://www.google.com/search?sxsrf=AB5stBhSueGnpREyC4D6DVHk34NFmoaxSw:1689696404193&q=oumuamua&tbm=isch&sa=X&ved=2ahUKEwjkzczP0ZiAAxVHMUQIHeFgC00Q0pQJegQIChAB

It keeps changing shape so it must be an advanced alien spacecraft.

 

[a a]

On Tuesday, 18 July 2023 at 07:05:05 UTC+2, Jan Panteltje wrote:

Former astronaut says it is \"extremely important\" to study artificial gravity
\"We have nothing in between one and zero.\"
https://arstechnica.com/space/2023/07/former-astronaut-says-its-extremely-important-to-study-artificial-gravity/

I agree with that
maybe even oumuamua rotates to create artificial gravity?

Right

prolong your sex time to 2 hours of artificial gravity study

 

[a a]

>

Yet one more #veryStupidByLowIQaa post.

 

[Jan Panteltje]

On a sunny day (Tue, 18 Jul 2023 09:11:13 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<57edbipnhqtns13oatcp31p7nurto9n7va@4ax.com>:

On Tue, 18 Jul 2023 05:04:58 GMT, Jan Panteltje <alien@comet.invalid
wrote:

Former astronaut says it is \"extremely important\" to study artificial gravity
\"We have nothing in between one and zero.\"
https://arstechnica.com/space/2023/07/former-astronaut-says-its-extremely-important-to-study-artificial-gravity/

I agree with that
maybe even oumuamua rotates to create artificial gravity?

I love all these high-resolution photographs:

https://www.google.com/search?sxsrf=AB5stBhSueGnpREyC4D6DVHk34NFmoaxSw:1689696404193&q=oumuamua&tbm=isch&sa=X&ved=2ahUKEwjkzczP0ZiAAxVHMUQIHeFgC00Q0pQJegQIChAB

Nice!


>It keeps changing shape so it must be an advanced alien spacecraft.

Would some human being from say 1000 years ago recognise a 747 high up in the sky?
Maybe would think it was a bird?

 

[Martin Brown]

On 18/07/2023 06:04, Jan Panteltje wrote:

Former astronaut says it is \"extremely important\" to study artificial gravity
\"We have nothing in between one and zero.\"
https://arstechnica.com/space/2023/07/former-astronaut-says-its-extremely-important-to-study-artificial-gravity/

I agree with that
maybe even oumuamua rotates to create artificial gravity?

The only way to do it is have a big enough cylindrical vehicle and spin
it like a centrifuge so that you are stuck to the floor. There are other
problems living in a rotating frame of reference though like being even
more dizzy than being in space already makes you.

As R increases things get more normal but we can\'t realistically build
anything big enough to work right now. Manned spaceflight is a luxury
and mostly a waste of scarce resources much ISS \"science\" research
wouldn\'t pass muster at a high school science fair.

Robotic space exploration is way more efficient and doesn\'t require
expensive and difficult life support systems for the duration.

I went to see Tim Peake\'s lecture on his mission to the ISS (just out of
lockdown I) - very entertaining with a sound system that can reproduce
launch sounds. Not so good for the theatre ceiling though.

Worth seeing if you get the chance...
even if you think ISS is a boondoggle.

--
Martin Brown

 

[Martin Brown]

On 20/07/2023 11:21, upsidedown@downunder.com wrote:

On Thu, 20 Jul 2023 08:29:31 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 18/07/2023 06:04, Jan Panteltje wrote:
Former astronaut says it is \"extremely important\" to study artificial gravity
\"We have nothing in between one and zero.\"
https://arstechnica.com/space/2023/07/former-astronaut-says-its-extremely-important-to-study-artificial-gravity/

I agree with that
maybe even oumuamua rotates to create artificial gravity?

The only way to do it is have a big enough cylindrical vehicle and spin
it like a centrifuge so that you are stuck to the floor. There are other
problems living in a rotating frame of reference though like being even
more dizzy than being in space already makes you.

As R increases things get more normal but we can\'t realistically build
anything big enough to work right now.

Why not use two identical spacecraft and put a 100 to 1000 m wire
between them and put the whole system rotating around each other ?

When going to e.g.Mars, spin it more slowly to simulate same gravity
as on Mars and when returning back to Earth spin it faster to simulate
1 G.

You could possibly do that at the expense of having two ships with crews
that are isolated from each other. The tether better hadn\'t snap!

But one has to ask, what is the point of sending people to Mars ?

Until there is something found that modern robotics and AI cannot deal
with nothing apart from the kudos of being the first to do it.

My suspicion is that they would have to build a robotic hospital there
first to care for the astronauts after they arrive!

It will be a bit like one of those crazy reality TV shows but with real
teeth if the participants fall out with each other (as seems likely in
the confined environment of space travel and timescales involved).

You have been asked to leave the house - the airlock is over there!

--
Martin Brown

 

[server]

On Thu, 20 Jul 2023 20:23:51 +0100, Martin Brown
<\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 20/07/2023 11:21, upsidedown@downunder.com wrote:
On Thu, 20 Jul 2023 08:29:31 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 18/07/2023 06:04, Jan Panteltje wrote:
Former astronaut says it is \"extremely important\" to study artificial gravity
\"We have nothing in between one and zero.\"
https://arstechnica.com/space/2023/07/former-astronaut-says-its-extremely-important-to-study-artificial-gravity/

I agree with that
maybe even oumuamua rotates to create artificial gravity?

The only way to do it is have a big enough cylindrical vehicle and spin
it like a centrifuge so that you are stuck to the floor. There are other
problems living in a rotating frame of reference though like being even
more dizzy than being in space already makes you.

As R increases things get more normal but we can\'t realistically build
anything big enough to work right now.

Why not use two identical spacecraft and put a 100 to 1000 m wire
between them and put the whole system rotating around each other ?

When going to e.g.Mars, spin it more slowly to simulate same gravity
as on Mars and when returning back to Earth spin it faster to simulate
1 G.

You could possibly do that at the expense of having two ships with crews
that are isolated from each other. The tether better hadn\'t snap!

The spacecraft masses doesn\'t have to be identical, so it might be
possible to put the full crew in a single spacecraft.

In 1966 the Gemini 11 was tethered to the Agena docking target with a
30 m tether. The rotation sped was very low and hence the artificial
gravity was minuscule.

https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-081A

 

[Joe Gwinn]

On Thu, 20 Jul 2023 20:23:51 +0100, Martin Brown
<\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 20/07/2023 11:21, upsidedown@downunder.com wrote:
On Thu, 20 Jul 2023 08:29:31 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 18/07/2023 06:04, Jan Panteltje wrote:
Former astronaut says it is \"extremely important\" to study artificial gravity
\"We have nothing in between one and zero.\"
https://arstechnica.com/space/2023/07/former-astronaut-says-its-extremely-important-to-study-artificial-gravity/

I agree with that
maybe even oumuamua rotates to create artificial gravity?

The only way to do it is have a big enough cylindrical vehicle and spin
it like a centrifuge so that you are stuck to the floor. There are other
problems living in a rotating frame of reference though like being even
more dizzy than being in space already makes you.

As R increases things get more normal but we can\'t realistically build
anything big enough to work right now.

Why not use two identical spacecraft and put a 100 to 1000 m wire
between them and put the whole system rotating around each other ?

When going to e.g.Mars, spin it more slowly to simulate same gravity
as on Mars and when returning back to Earth spin it faster to simulate
1 G.

You could possibly do that at the expense of having two ships with crews
that are isolated from each other. The tether better hadn\'t snap!

But one has to ask, what is the point of sending people to Mars ?

Until there is something found that modern robotics and AI cannot deal
with nothing apart from the kudos of being the first to do it.

My suspicion is that they would have to build a robotic hospital there
first to care for the astronauts after they arrive!

It will be a bit like one of those crazy reality TV shows but with real
teeth if the participants fall out with each other (as seems likely in
the confined environment of space travel and timescales involved).

You have been asked to leave the house - the airlock is over there!

Hmm. Look up the \"air tax\" in \"The Moon is a Harsh Mistress\" by
Heinlein.

Joe Gwinn

 

[Phil Hobbs]

<upsidedown@downunder.com> wrote:

On Thu, 20 Jul 2023 20:23:51 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 20/07/2023 11:21, upsidedown@downunder.com wrote:
On Thu, 20 Jul 2023 08:29:31 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 18/07/2023 06:04, Jan Panteltje wrote:
Former astronaut says it is \"extremely important\" to study artificial gravity
\"We have nothing in between one and zero.\"
https://arstechnica.com/space/2023/07/former-astronaut-says-its-extremely-important-to-study-artificial-gravity/

I agree with that
maybe even oumuamua rotates to create artificial gravity?

The only way to do it is have a big enough cylindrical vehicle and spin
it like a centrifuge so that you are stuck to the floor. There are other
problems living in a rotating frame of reference though like being even
more dizzy than being in space already makes you.

As R increases things get more normal but we can\'t realistically build
anything big enough to work right now.

Why not use two identical spacecraft and put a 100 to 1000 m wire
between them and put the whole system rotating around each other ?

When going to e.g.Mars, spin it more slowly to simulate same gravity
as on Mars and when returning back to Earth spin it faster to simulate
1 G.

You could possibly do that at the expense of having two ships with crews
that are isolated from each other. The tether better hadn\'t snap!

The spacecraft masses doesn\'t have to be identical, so it might be
possible to put the full crew in a single spacecraft.

In 1966 the Gemini 11 was tethered to the Agena docking target with a
30 m tether. The rotation sped was very low and hence the artificial
gravity was minuscule.

https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-081A

Equal masses give you the lowest-energy solution.

The point of the large radius is to reduce the nasty Coriolis effect when
you get out of bed and stand up, for instance.

The two-mass system rotates about its center of mass. To get the same
effect with a 10x smaller counterweight, it has to be 5.5 times farther
away (1:10 vs. 1:1), and move at 10x faster tangential speed.

That takes 5.5 times more energy.

It’s cheaper than that in delta-V terms, but still a harder problem.

I expect that the worst part would be orbital maneuvering once the vehicle
has been spun up.

Cheers

Phil Hobbs



--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

 

[Phil Hobbs]

Joe Gwinn <joegwinn@comcast.net> wrote:

On Thu, 20 Jul 2023 20:23:51 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 20/07/2023 11:21, upsidedown@downunder.com wrote:
On Thu, 20 Jul 2023 08:29:31 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 18/07/2023 06:04, Jan Panteltje wrote:
Former astronaut says it is \"extremely important\" to study artificial gravity
\"We have nothing in between one and zero.\"
https://arstechnica.com/space/2023/07/former-astronaut-says-its-extremely-important-to-study-artificial-gravity/

I agree with that
maybe even oumuamua rotates to create artificial gravity?

The only way to do it is have a big enough cylindrical vehicle and spin
it like a centrifuge so that you are stuck to the floor. There are other
problems living in a rotating frame of reference though like being even
more dizzy than being in space already makes you.

As R increases things get more normal but we can\'t realistically build
anything big enough to work right now.

Why not use two identical spacecraft and put a 100 to 1000 m wire
between them and put the whole system rotating around each other ?

When going to e.g.Mars, spin it more slowly to simulate same gravity
as on Mars and when returning back to Earth spin it faster to simulate
1 G.

You could possibly do that at the expense of having two ships with crews
that are isolated from each other. The tether better hadn\'t snap!

But one has to ask, what is the point of sending people to Mars ?

Until there is something found that modern robotics and AI cannot deal
with nothing apart from the kudos of being the first to do it.

My suspicion is that they would have to build a robotic hospital there
first to care for the astronauts after they arrive!

It will be a bit like one of those crazy reality TV shows but with real
teeth if the participants fall out with each other (as seems likely in
the confined environment of space travel and timescales involved).

You have been asked to leave the house - the airlock is over there!

Hmm. Look up the \"air tax\" in \"The Moon is a Harsh Mistress\" by
Heinlein.

Joe Gwinn

Blech. Heinlein was really good at imagining horrific dystopias and then
sugar-coating them for young male audiences.

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

 

[Anthony William Sloman]

On Friday, July 21, 2023 at 9:40:00 AM UTC+10, Phil Hobbs wrote:

Joe Gwinn <joeg...@comcast.net> wrote:
On Thu, 20 Jul 2023 20:23:51 +0100, Martin Brown <\'\'\'newspam\'\'\'@nonad.co.uk> wrote:
On 20/07/2023 11:21, upsid...@downunder.com wrote:
On Thu, 20 Jul 2023 08:29:31 +0100, Martin Brown <\'\'\'newspam\'\'\'@nonad.co.uk> wrote:
On 18/07/2023 06:04, Jan Panteltje wrote:

<snip>

You have been asked to leave the house - the airlock is over there!

Hmm. Look up the \"air tax\" in \"The Moon is a Harsh Mistress\" by Heinlein.

Blech. Heinlein was really good at imagining horrific dystopias and then sugar-coating them for young male audiences.

He was even odder than that makes him sound.

https://en.wikipedia.org/wiki/Stranger_in_a_Strange_Land

was his most successful book, and it is very odd indeed.

--
Bill Sloman, Sydney

 

[Martin Brown]

On 21/07/2023 00:39, Phil Hobbs wrote:

upsidedown@downunder.com> wrote:
On Thu, 20 Jul 2023 20:23:51 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 20/07/2023 11:21, upsidedown@downunder.com wrote:

When going to e.g.Mars, spin it more slowly to simulate same gravity
as on Mars and when returning back to Earth spin it faster to simulate
1 G.

You could possibly do that at the expense of having two ships with crews
that are isolated from each other. The tether better hadn\'t snap!

The spacecraft masses doesn\'t have to be identical, so it might be
possible to put the full crew in a single spacecraft.

In 1966 the Gemini 11 was tethered to the Agena docking target with a
30 m tether. The rotation sped was very low and hence the artificial
gravity was minuscule.

https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-081A


Equal masses give you the lowest-energy solution.

But he does have a point.

The other equal mass could be just that and quite compact. A lump of
lead or depleted uranium for example in an otherwise passive vehicle.

The point of the large radius is to reduce the nasty Coriolis effect when
you get out of bed and stand up, for instance.

My university supervisor worked on early radar in a hut on the rotating
antenna during WWII and had stories of knocking himself out with a
spanner after forgetting that he was in a rotating frame of reference.

The two-mass system rotates about its center of mass. To get the same
effect with a 10x smaller counterweight, it has to be 5.5 times farther
away (1:10 vs. 1:1), and move at 10x faster tangential speed.

That takes 5.5 times more energy.

It’s cheaper than that in delta-V terms, but still a harder problem.

I expect that the worst part would be orbital maneuvering once the vehicle
has been spun up.

Fly by wire could handle it but you had better get the thing pretty well
lined up on its target since course corrections would be \"interesting\".
You really wouldn\'t want to make a major one.

--
Martin Brown

 

[John Larkin]

On Fri, 21 Jul 2023 11:12:51 +0100, Martin Brown
<\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 21/07/2023 00:39, Phil Hobbs wrote:
upsidedown@downunder.com> wrote:
On Thu, 20 Jul 2023 20:23:51 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 20/07/2023 11:21, upsidedown@downunder.com wrote:

When going to e.g.Mars, spin it more slowly to simulate same gravity
as on Mars and when returning back to Earth spin it faster to simulate
1 G.

You could possibly do that at the expense of having two ships with crews
that are isolated from each other. The tether better hadn\'t snap!

The spacecraft masses doesn\'t have to be identical, so it might be
possible to put the full crew in a single spacecraft.

In 1966 the Gemini 11 was tethered to the Agena docking target with a
30 m tether. The rotation sped was very low and hence the artificial
gravity was minuscule.

https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-081A


Equal masses give you the lowest-energy solution.

But he does have a point.

The other equal mass could be just that and quite compact. A lump of
lead or depleted uranium for example in an otherwise passive vehicle.

The point of the large radius is to reduce the nasty Coriolis effect when
you get out of bed and stand up, for instance.

My university supervisor worked on early radar in a hut on the rotating
antenna during WWII and had stories of knocking himself out with a
spanner after forgetting that he was in a rotating frame of reference.

The two-mass system rotates about its center of mass. To get the same
effect with a 10x smaller counterweight, it has to be 5.5 times farther
away (1:10 vs. 1:1), and move at 10x faster tangential speed.

That takes 5.5 times more energy.

It’s cheaper than that in delta-V terms, but still a harder problem.

I expect that the worst part would be orbital maneuvering once the vehicle
has been spun up.

Fly by wire could handle it but you had better get the thing pretty well
lined up on its target since course corrections would be \"interesting\".
You really wouldn\'t want to make a major one.

People are the worst gadgets to send into space.

 

[Anthony William Sloman]

On Friday, July 21, 2023 at 9:13:24 PM UTC+10, John Larkin wrote:

On Fri, 21 Jul 2023 11:12:51 +0100, Martin Brown<\'\'\'newspam\'\'\'@nonad.co.uk> wrote:
On 21/07/2023 00:39, Phil Hobbs wrote:
upsid...@downunder.com> wrote:
On Thu, 20 Jul 2023 20:23:51 +0100, Martin Brown <\'\'\'newspam\'\'\'@nonad..co.uk> wrote:
On 20/07/2023 11:21, upsid...@downunder.com wrote:

<snip>

> People are the worst gadgets to send into space.

But the most flexible, if you pick the right people.

--
Bill Sloman, Sydney

 

[Phil Hobbs]

On 2023-07-21 06:12, Martin Brown wrote:

On 21/07/2023 00:39, Phil Hobbs wrote:
upsidedown@downunder.com> wrote:
On Thu, 20 Jul 2023 20:23:51 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 20/07/2023 11:21, upsidedown@downunder.com wrote:

When going to e.g.Mars, spin it more slowly to simulate same gravity
as on Mars and when returning back to Earth spin it faster to simulate
1 G.

You could possibly do that at the expense of having two ships with
crews
that are isolated from each other. The tether better hadn\'t snap!

The spacecraft masses doesn\'t have to be identical, so it might be
possible to put the full crew in a single spacecraft.

In 1966 the Gemini 11 was tethered to the Agena docking target with a
30 m tether. The rotation sped was very low and hence the artificial
gravity was minuscule.

https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-081A


Equal masses give you the lowest-energy solution.

But he does have a point.

The other equal mass could be just that and quite compact. A lump of
lead or depleted uranium for example in an otherwise passive vehicle.

Seems like a huge waste of delta-V, though. The other vehicle could
hold stores, for instance. It might not even have to be pressurized.
Something like the automated racks used in warehouses could make that
relatively painless. (Relatively, now, relatively.)

The point of the large radius is to reduce the nasty Coriolis effect when
you get out of bed and stand up, for instance.

My university supervisor worked on early radar in a hut on the rotating
antenna during WWII and had stories of knocking himself out with a
spanner after forgetting that he was in a rotating frame of reference.

Being young and energetic is a handicap in that environment, I bet.

The two-mass system rotates about its center of mass. To get the same
effect with a 10x smaller counterweight, it has to be 5.5 times farther
away (1:10 vs. 1:1), and move at 10x faster tangential speed.

That takes 5.5 times more energy.

It’s cheaper than that in delta-V terms, but still a harder problem.

I expect that the worst part would be orbital maneuvering once the
vehicle
has been spun up.

Fly by wire could handle it but you had better get the thing pretty well
lined up on its target since course corrections would be \"interesting\".
You really wouldn\'t want to make a major one.

You do have to handle Mars orbit injection, at least. Getting rid of
all that angular momentum would take a lot of delta-V, or else a very
very heavy reaction wheel.

The Clarke/Kubrick solution (rotating hoop with a non-rotating garage at
the hub) has its points. You need a landing / ascent vehicle, plus a
whole lot of delta-V for the return trip. You\'d need to put that in the
hub portion, for sure.

If you have the fuel tanks rotating, you need to be very very careful
about rotational stability. A rotating system with internal dissipation
(due e.g. to fuel sloshing around) very rapidly changes its angular
velocity vector to be along the largest principal axis of the inertia
tensor. For instance, a long skinny tank rotating about its
longitudinal axis will wind up tumbling end over end.

The math for this is really pretty--small deviations from perfect axial
rotation initially grow exponentially. You fix that by rotating about
the stable axis, because trying to do active control is too risky.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Fri, 21 Jul 2023 10:12:39 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-07-21 06:12, Martin Brown wrote:
On 21/07/2023 00:39, Phil Hobbs wrote:
upsidedown@downunder.com> wrote:
On Thu, 20 Jul 2023 20:23:51 +0100, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 20/07/2023 11:21, upsidedown@downunder.com wrote:

When going to e.g.Mars, spin it more slowly to simulate same gravity
as on Mars and when returning back to Earth spin it faster to simulate
1 G.

You could possibly do that at the expense of having two ships with
crews
that are isolated from each other. The tether better hadn\'t snap!

The spacecraft masses doesn\'t have to be identical, so it might be
possible to put the full crew in a single spacecraft.

In 1966 the Gemini 11 was tethered to the Agena docking target with a
30 m tether. The rotation sped was very low and hence the artificial
gravity was minuscule.

https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-081A


Equal masses give you the lowest-energy solution.

But he does have a point.

The other equal mass could be just that and quite compact. A lump of
lead or depleted uranium for example in an otherwise passive vehicle.

Seems like a huge waste of delta-V, though. The other vehicle could
hold stores, for instance. It might not even have to be pressurized.
Something like the automated racks used in warehouses could make that
relatively painless. (Relatively, now, relatively.)

The point of the large radius is to reduce the nasty Coriolis effect when
you get out of bed and stand up, for instance.

My university supervisor worked on early radar in a hut on the rotating
antenna during WWII and had stories of knocking himself out with a
spanner after forgetting that he was in a rotating frame of reference.

Being young and energetic is a handicap in that environment, I bet.

The two-mass system rotates about its center of mass. To get the same
effect with a 10x smaller counterweight, it has to be 5.5 times farther
away (1:10 vs. 1:1), and move at 10x faster tangential speed.

That takes 5.5 times more energy.

It’s cheaper than that in delta-V terms, but still a harder problem.

I expect that the worst part would be orbital maneuvering once the
vehicle
has been spun up.

Fly by wire could handle it but you had better get the thing pretty well
lined up on its target since course corrections would be \"interesting\".
You really wouldn\'t want to make a major one.

You do have to handle Mars orbit injection, at least. Getting rid of
all that angular momentum would take a lot of delta-V, or else a very
very heavy reaction wheel.

The Clarke/Kubrick solution (rotating hoop with a non-rotating garage at
the hub) has its points. You need a landing / ascent vehicle, plus a
whole lot of delta-V for the return trip. You\'d need to put that in the
hub portion, for sure.

If you have the fuel tanks rotating, you need to be very very careful
about rotational stability. A rotating system with internal dissipation
(due e.g. to fuel sloshing around) very rapidly changes its angular
velocity vector to be along the largest principal axis of the inertia
tensor. For instance, a long skinny tank rotating about its
longitudinal axis will wind up tumbling end over end.

The math for this is really pretty--small deviations from perfect axial
rotation initially grow exponentially. You fix that by rotating about
the stable axis, because trying to do active control is too risky.

Cheers

Phil Hobbs

The mass balance will also be upset as you transfer dead bodies
between the vehicles.

 

[Martin Brown]

On 21/07/2023 15:12, Phil Hobbs wrote:

If you have the fuel tanks rotating, you need to be very very careful
about rotational stability.  A rotating system with internal dissipation
(due e.g. to fuel sloshing around) very rapidly changes its angular
velocity vector to be along the largest principal axis of the inertia
tensor.  For instance, a long skinny tank rotating about its
longitudinal axis will wind up tumbling end over end.
The math for this is really pretty--small deviations from perfect axial
rotation initially grow exponentially.  You fix that by rotating about
the stable axis, because trying to do active control is too risky.

I have the distinct feeling that at some stage in our academic careers
we encountered the same (visiting?) lecturer on slender body dynamics
and turbulence. His other big interest on the turbulent flow side was
Pade (aka Shanks) transform for turning hard won analytic but divergent
polynomial \"solutions\" into something that engineers could actually use!

I got good value out of his course but his name escapes me now.

--
Martin Brown

 

[Phil Hobbs]

Martin Brown <\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 21/07/2023 15:12, Phil Hobbs wrote:

If you have the fuel tanks rotating, you need to be very very careful
about rotational stability.  A rotating system with internal dissipation
(due e.g. to fuel sloshing around) very rapidly changes its angular
velocity vector to be along the largest principal axis of the inertia
tensor.  For instance, a long skinny tank rotating about its
longitudinal axis will wind up tumbling end over end.
The math for this is really pretty--small deviations from perfect axial
rotation initially grow exponentially.  You fix that by rotating about
the stable axis, because trying to do active control is too risky.

I have the distinct feeling that at some stage in our academic careers
we encountered the same (visiting?) lecturer on slender body dynamics
and turbulence. His other big interest on the turbulent flow side was
Pade (aka Shanks) transform for turning hard won analytic but divergent
polynomial \"solutions\" into something that engineers could actually use!

I got good value out of his course but his name escapes me now.

I’ve never taken a course like that, alas. I learned most of what I know
about it from regular classical mechanics classes. Profs were folks such
as Fred Kaempffer and Dirk Walecka. Asymptotic methods, series summation,
and so on, I mostly learned from an EE-turned-Margo, Stefanos Venakides
(may his tribe i).

I did do a fun class on orbital mechanics with Michael Ovenden, but it was
mostly planetary systems and globular star clusters. He also taught
galactic dynamics (also a fun class).

One guy you might know is Gordon Walker, who taught an instruments class.

I owe those guys a lot.

Cheers

Phil Hobbs



--
Dr Philip C D Hobbs Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics,
Electro-optics, Photonics, Analog Electronics

 

[John Larkin]

On Sun, 23 Jul 2023 13:51:18 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Martin Brown <\'\'\'newspam\'\'\'@nonad.co.uk> wrote:
On 21/07/2023 15:12, Phil Hobbs wrote:

If you have the fuel tanks rotating, you need to be very very careful
about rotational stability.  A rotating system with internal dissipation
(due e.g. to fuel sloshing around) very rapidly changes its angular
velocity vector to be along the largest principal axis of the inertia
tensor.  For instance, a long skinny tank rotating about its
longitudinal axis will wind up tumbling end over end.
The math for this is really pretty--small deviations from perfect axial
rotation initially grow exponentially.  You fix that by rotating about
the stable axis, because trying to do active control is too risky.

I have the distinct feeling that at some stage in our academic careers
we encountered the same (visiting?) lecturer on slender body dynamics
and turbulence. His other big interest on the turbulent flow side was
Pade (aka Shanks) transform for turning hard won analytic but divergent
polynomial \"solutions\" into something that engineers could actually use!

I got good value out of his course but his name escapes me now.


I’ve never taken a course like that, alas. I learned most of what I know
about it from regular classical mechanics classes. Profs were folks such
as Fred Kaempffer and Dirk Walecka. Asymptotic methods, series summation,
and so on, I mostly learned from an EE-turned-Margo, Stefanos Venakides
(may his tribe i).

I did do a fun class on orbital mechanics with Michael Ovenden, but it was
mostly planetary systems and globular star clusters. He also taught
galactic dynamics (also a fun class).

One guy you might know is Gordon Walker, who taught an instruments class.

I owe those guys a lot.

Cheers

Phil Hobbs

Does clestial mechanics include the time-lag caused by the finite
speed of gravity? As if the many-body problem wasn\'t bad enough
already.