Lifeboats in Space

(Henry Spencer) wrote:

If you have reliable but not-too-swift transportation, it makes a lot of
sense to subdivide the station (and life support, and essential supplies)
so that if part of the station becomes uninhabitable, you retreat to the
habitable part and simply wait for rescue.

In fact, USN submarine design follows just this practice. Every
watertight compartment with an escape chamber has a source of O2, a
method of removing CO2, food, water, and lifejackets/escape apparatus
for for (IIRC) 75% of the crew.

Doctrine is that in general you retreat to a liveable portion and
trust in your communications systems to alert rescue forces. You only
escape individually if no other option exists.

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

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

"Derek Lyons" wrote in message
...
-Significant manuevering margins for one. (Both for minor
phasing and plane burns, and boosting.)

The above is the only requirement of yours that I question a bit.

Movie "escape pod" scenes don't depict reality. The reality is that your
space station is highly unlikely to ever go "boom" and a "dead" station
won't be going anywhere. That said, the lifeboat could remain attached to
the station while the crew awaits rescue. This is the origin of the "safe
haven" concept. Once you assume you'll stay attached to the station, you
can make just about any pressurized module double as your lifeboat.

I still think making it a separate (sealed) module is nice because it helps
insure that it is always ready to be used for an emergency. Otherwise, you
may find yourself in an emergency, but the safe haven is packed with so much
junk that you can't use it without getting the junk out. You'd be in a
hurry throwing out the junk if the station module attached to the lifeboat
was leaking atmosphere.

I suppose if you must include a requirement to operate completely
independant of the station (including no physical attachment), then you'd
need a minimum of two burns. One to boost you away from the station, and
another half an orbit later to make sure you don't recontact the station
after one orbit. That said, just how much delta-V you'd need depends on how
far away you want to get from the station. Once you're safely away from the
station, you really don't need any additional delta-V. You just wait for a
rescue.

Fuel for raising the orbit could be necessary, depending on the altitude of
the station. If the station is in high enough orbit that the expected
orbital decay of the lifeboat is, say, more than two times that of the
longest possible stay in orbit (life support limits for one person in the
lifeboat), I'd think you wouldn't need additional capability to raise your
orbit.

The above said, it may be desirable to require that a free flying lifeboat
be designed with moments of inertia such that its attitude would be gravity
gradient stabilized (the most passive means of attitude control that I know
of). Furthermore, any venting should be non-propulsive. This insures that
the lifeboat won't be tumbling, even if it runs out of attitude control
propellant.

Just my $0.02 before I leave for the weekend. ;-)

Jeff

(George William Herbert) :

In article ,
Earl Colby Pottinger wrote:
If you were designing a lifeboat for a space station that you don't expect
to
return to Earth, just keep it passengers alive until help comes. What
would
you think the basic requirement be.

One thing you should do before doing this...

Trade off the weight of TPS and recovery gear with the weight of
the life support endurance and systems endurance to sit on orbit
for a specified time.

In the end, the reentry just isn't that expensive.

Should this be in sci.space.tech? I am not asking for the design it, that
is
clearly a tech thread. Is basic requirements a policy thread?

If you want to post or crosspost i'd think it's entirely
on topic there and would approve it...

What does it take to ensure they land near help?

Earl Colby Pottinger

--
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Ian Stirling wrote:

A really trivial "ELCSS", that just consisted of a bag and a breath-mask,
and a hose overboard, so that you breath each volume of O2 three
times before it goes overboard would need you to use about 150Kg of O2
per person before things started getting noticable.
Say 10l/min, divided by 3 is 3l/min.
Or about 3g/min, or 4.5Kg/day.
So, closing on a couple of months.

So we have established that oxygen is not really the limiting factor

I guess the ideal one would have passive cooling / heating and CO2
removal as backup (at the very least), so that even if thre is a trouble
with solar cells you would still survive, just possibly for a shorter
time.

Other considerations:
* collect urine and dump it overboard - way simpler and also
lets you dump some of the waste heat from the humans

* humans will need some kind of entertainment

* if there is debris from teh station, you really want to change
the orbit

--
Sander

+++ Out of cheese error +++

Earl Colby Pottinger wrote:
(George William Herbert) :
[...]
Trade off the weight of TPS and recovery gear with the weight of
the life support endurance and systems endurance to sit on orbit
for a specified time.

In the end, the reentry just isn't that expensive.

What does it take to ensure they land near help?

Minimally?

A Palmpilot or equivalent, a small bit of custom software,
a kilogram of GPS, some gas jet maneuvering thrusters,
and a small solid rocket.

Even a purely ballistic reentry is accurate enough for
"near help".


-george william herbert

"Earl Colby Pottinger" wrote in message
...
"Christian Ramos" :

"Earl Colby Pottinger" wrote in message
...
If you were designing a lifeboat for a space station that you don't
expect to return to Earth, just keep it passengers alive until help comes.
What
would you think the basic requirement be.

I'll have a go off the top of my head,

Single compartment.

Simple is best, so yes.

Basic survival rations for sustanance

Ofcourse, stored food and water.

I'll list what I was thinking at the time. Although, storing that much water
for an undertimed amount of people for and undefined amount of time may be
difficult, especially when taking into account medical requirements etc. I'd
prefer more options for water. Water is life as the old saying goes.

Small Manual Urine processor, low efficiency OK

Why not just dump it out a valve?

You can survive along time with limited amounts of food but not without
water. Given an unknown period of stay and an unknown amount of people seems
like it would provide a number of useful options. Example, say your water
tank is hit, you have a method of extended survival. Another example, say a
lifeboat for 4 people and their are 6 people, the urine processing could
provide the difference between leaving people behind etc.

Reusable Airlock for storage and ejection of wastes and bodies, also
cycles
independant of internal

Most wastes don't and airlock the size needed to get rid of bodies,
besides
is the thermal control setup allows a passive cold storage unit to be
added
maybe it is better to bring down the bodies instead of scattering thier
remains all over the place.

Passive cold storage would probably require attitude control and the
assumption of no damage to the passive shielding. Perhaps not as likely in
an emergency situation.

If it fails you can place the whole crew at risk, human bodies are rather
toxic as they decompose let alone the morale issues, additionally in some
emergency procedures your going to have amounts of medical waste and other
biological hazards that you probably dont want anywhere near passengers.
Note: I was going for absolute minimal survival mode.

You could have bleed valves and other such items in exchange for more
failure points, I was thinking a simple airlock for storage of appropriate
streams and evacuation of the airlock once capacity got full. If the airlock
can cycle off the internal compartment it also provides away of bleeding out
contaminations or other accidents internally.

Docking port connected to Airlock that support manual and automatic
including embilicals

? Why does docking port and airlock must be connected? Why must there be
embilicals?

In a scenario where immediate rescue is not possible, I thought it would be
important to have the ability to for an unmanned vehicle to dock with the
craft and also have the ability to supply consumables, eg: O2. When I say
connected, I may be misspeaking, what I envisaged was only the airlock
between the main lifeboat compartment and the "other" spacecraft.

Additionally, I was thinking of ingress to the lifeboat at that docking
point.

Non-directional Communications with passive locator beacon

Okay.

Basic Life Support restricted to processing CO2 via consumable or vacuum
regenerable cartridges

Where does the missing oxygen come from then? Good point about
regenerable
carts, with a vacuum on the outside they would be easy to process.

Great engineer I'd make..A lifeboat without oxygen, not good. I'd made the
assumption that their was a store of oxygen, and only oxygen present in the
lifeboat, probably a cryogenic store. Vacuum processing as with other
external interactions I envisaged occuring through the airlock.

Life Support cartidges interchangeable with cabin and mask system

Possible ?????

Anything possible. It would depend on the original design. I "believe" that
this is important enough to put some engineering time into. I'd considered
the possibility of systems failure in the cabin life support system,
especially, if blood and other types of contaminants made it into the
lifeboat.

Environmental system that captures humidity

Ok.

Solar cells for power that will recharge chemical batteries or feed
direct

Ok.

,also attitude independant Small flywheel or similar with manual
charging
and common adapter to powered equipment

Why if you already have solar cells?

Say damage to energy distribution or the energy system itself, you could
still power lifesupport communications or provide sufficient power for
airlock opening. Some medical equipment can be energy hogs, so it may be
useful there in providing additional energy to the baseline power supply.
Some other types of faults, your orbit may give a recharging window that may
not provide sufficient power to run everything full time all the time, so
you could power things down, but you wouldnt want to power down medical
equipment.

To summarise my rambling, such a energy storage device could provide topup,
backup for main system failure or emergency power. Given manual charging or
cranking in this case, it makes it independant of the external environment
or interal power distribution. Worst case scenario, you have a power system
that only requires a human is present and viable.

Structural shape that would naturally stabilise, maybe gravity gradient
or
dampeners

Not Structural shape not big enought, gravity booms should work fine.

Great..Would these need to be deployed or would these be passive?

Basic painkillers, trauma medication etc combined with electronic
diagnostic
equipment

Yes.

Sealable coveralls for all occupants.

Do you mean a mini short term space suit? Can we even make a general
model

Could be a space suit, but I was thinking more something to keep the bodily
fluids, (blood, vomit, urine etc) from floating around the cabin and
potentially becoming a threat to either the life support system or passenger
health. The problem with using a spacesuit is getting adequate access to the
patient, so I was thinking something not necessarily airtight but that would
contain any fluids originating from the wearer.

In fact, I had envisaged no space suits at all "required" with the lifeboat.

All equipment such as airlocks, diagnostics operable both internally,
externally and remotely.

And if possible without power.

Do you think it would be possible to run without power, eg: medical
diagnostic equipment, airlocks etc. This also dovetails into my little
cranking flywheel to provide extra boost for such systems.

Minimal to no active systems.

Yes.

No rocketry or attitude control, if required for pushoff,
limit to cold jets linked to integrated supply.

None? What about maintaining orbit or preventing drifting apart.

I know..Thoughts I had as well. But I was thinking lifeboat as something to
provide survival capabilities only. Depending on the nature of the
disaster, orbit while degrading should likely be viable for a reasonable
time. As for drifting apart I would have thought you would want this to some
degree, say a debris laden disaster. As long as the person can be tracked
shouldnt be a problem as long as they have orbital speed at pushoff, which
they should from a space station.

The issue with having orbital control is you need computers and hydraulics
to handle them, guidance and navigation systems and external sensors and
other complicated systems that may not survive pushoff from the disaster,
you also need someone who knows what their doing to "fly" it which may not
be available. Power requirements also go up. I guess my thinking is if you
go to the complexity of adding rocket and orbital control, you may as well
add the reentry shield and have it drop to earth rather than float in space.

Minimal computerisation or electronics

Should not depend on how much surplus power there is.

Personal bias. I'm reluctant to bet my life on electronics in an environment
which is hostile to electronics and to which are sensitive to factors which
cant be adequately predicted. eg: Internal heat generation may damage them.

This is for a lifeboat as opposed to a shelter.

Why not a shelter if that is the best answer?

Good question. It's something I've been thinking of lately in terms of a
permanent colony. What are the capabilities that would need to be present at
different levels of habitation, eg: mobile, lifeboat, shelter, vehicle, base
etc. Not sure I have an answer. How would you define the differences between
a spacecraft, shelter and a lifeboat.

I guess I see a lifeboat as a option of last resort, it should be as simple
and reliable as possible and focus solely on giving people a chance of
survival as long as possible. In the case of a shelter, I would think along
the lines as people have suggested of either seperating the station modules
etc. The lifeboat would be totally dependant on outside forces for anything
except survival. While analogies can be flawed, I'll use one here, on the
ocean I would see the lifeboat the same as the lifeboat in space and the
desert island on the ocean as the equivalent of a shelter in space.

If we ignore the inital requirements as stated, my preference would be a
single man pod, that has three functions, pushoff, reentry setup, landing.
That is, a pod that ejects away from the station and reenters the earth.

"Jeff Findley" wrote in message
...

The basic point is that you have to focus on the real requirements and not
specify solutions to those requirements. If you specify solutions, you
don't allow room for innovation and for creative problem solving that can
lead to cheaper and better solutions to the specified problems.


Absolutely fair and accurate statement. In this case, I had glossed over his
request for requirements and responded with potential solutions to the
requirements he had stated. So you are correct in what you said, but in my
defense I wasnt attempting to give him requirements but responding with
potential solutions to the requirements he stated.

I should read more carefully.

George William Herbert wrote:
Earl Colby Pottinger wrote:
(George William Herbert) :
[...]
Trade off the weight of TPS and recovery gear with the weight of
the life support endurance and systems endurance to sit on orbit
for a specified time.

In the end, the reentry just isn't that expensive.

What does it take to ensure they land near help?

Minimally?

A Palmpilot or equivalent, a small bit of custom software,
a kilogram of GPS, some gas jet maneuvering thrusters,
and a small solid rocket.

Tiny nitpick - palmpilot like devices with GPS are well under half
a kilo. (the GPS will need software modifications)

You don't even really need GPS, if you've got a palmpilot.
Palmpilot displays rotating globe, and you use a small optical instrument
to center the horizon to get a local vertical and observe straight down,
then compare continent crossings, and adjust the orbit model according
to observations.

Actually, the camera on the palmpilot-type device would probably be
adequate for this task, as well as attitude control. (at least on the
dayside)

GPS is better of course.

Even a purely ballistic reentry is accurate enough for
"near help".

In article ,
Christian Ramos wrote:
Small Manual Urine processor, low efficiency OK
Why not just dump it out a valve?

You can survive along time with limited amounts of food but not without
water.

The problem is that processing urine back into potable water is actually
fairly complicated, and moreover takes significant amounts of power.

And the payoff is low: you need about 3.5 liters/man-day for food
rehydration, food preparation, and drinking -- maybe a bit less in
emergency conditions -- and urine reprocessing will get you back only
about 1.5.

It's better to put the mass into more stored water.

...Example, say your water tank is hit...

Tank, singular? Should be multiple tanks.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

"Henry Spencer" wrote in message
...

...Example, say your water tank is hit...

Tank, singular? Should be multiple tanks.

Even if it's not.. how many failures exactly are we expected to plan
against.

--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |