External Tanks in Orbit

March 1999 External Tank Newsgroup Discussion

Subject: External Tanks, Space Hotels, and Roton.
March 9 - March 21, 1999
(quotations were extracted from the sci.space.policy or sci.space.tech newsgroups and have been edited for content)

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Subject: Roton and Shuttle ETs
From: Eamon Patrick Watters <p9392394@fujin.qub.ac.uk>
Date: Tue, 9 Mar 1999 12:59:29 +0000

There's an article on the BBC's online website that the Hilton and British
Airways are interested in Space Island's ET Wheel Station:

http://news.bbc.co.uk/hi/english/sci/tech/newsid_293000/293366.stm

I'd been thinking that if Roton achieved all it said it could, it would
still be just a good satelite launcher, or a joyride machine - but it
occured to me it would be an ideal ET refurbishment vehicle. If a shuttle
deposited it's tank in LEO, the roton could rendezvous and drop a team off
to do some internal decorating. I know this analysis is very simlistic -
but the idea of Roton enabling large space structures to be build (albeit
ET derived) is very appealing.

Whad do y'all think?

Eamon Watters.

========
To: sci-space-tech@moderators.uu.net
Newsgroups: sci.space.policy,sci.space.tech,sci.space.shuttle
Subject: External Tanks, Space Hotels, and Roton.
From: Thomas Moore <t_moore@bellsouth.net>
Date: Wed, 10 Mar 1999 03:13:44 GMT

As someone else already mentioned today, Hilton Hotels seems to be
interested in a ET based space hotel. I have broken the thread out
seperately. For those who haven't read the article, it can be found at:

http://news.bbc.co.uk/hi/english/sci/tech/newsid_293000/293366.stm

The post went on to comment about Roton being able to support the
outfitting of such a venture. I commented on this back in the December
ET debate. (For review of the highlights check out Cris Fitch's ET web
site,

( http://www.triptyk.com/crisf/text/et_orbit.htm )

where you will also find a link to an earlier BBC article on Hilton and
the ET station designs.

Roton, and other small manned launchers have a distinct advantage over
the shuttle for station operations. They allow for a regular cargo
service to the station with payloads in the 7000lb range. Just about
right for consumables, crew replacement, raw materials for
manufacturing, and manufactured goods. These missions make up the
majority of the missions to a commercial station. A Roton sized launch
vehicle makes a commercial station much more likely to make a profit.
And of course, profit is what will make a commercial station more likely
to be built.

Thats one of the reasons an ET based station design is so popular. By
converting and reusing the discarded ET tanks, large volumes of usable
space are added to the station for low cost. A low cost allows more of
your gross from products to go into profit.

But lets take a look at that ET wheel that is displayed with the BBC
article. Pretty isn't it? Very unlikely however. Why you ask? Well the
biggest problem with that particular station is that it requires 13
tanks to build. Since 3/4 of the shuttle fleet is off playing at ISS
(which is not a good place to build this... the payload penalties are
too high for a commercial station) that leaves only Columbia to build
it. Even if Columbia could maximize on 2 flights per year, it would
take 6.5 years at a minimum to complete the ring. But Columbia won't
be available for all those flights. NASA has other things they want
Columbia to do. If a commercial station were to be built with ET's, the
most reasonable figure would be a station constructed with 2 tanks, 3 at
a maximum. Even with 3 tanks, the station could potentially be over 3
times the size of ISS! Just one tank is enough to construct a station
for commercial purposes.

In December, I proposed a design that lends itself well to such a 1-3
tank station. It's extremely cost effective, requiring very minimal
alterations to the ET. Not only are minimal alterations more cost
effective, they reduce safety impacts. This is a MAJOR issue. I have
taken my viewpoints from the ET debate and put together a series of
drawings showing the station under construction. I also put together a
little story to make the construction details a little more fun. No its
not a great story, but its more fun then straight technical
descriptions. The story and pictures can be found at:

http://www.starsysfw.com/space/vulcan.htm

For those that want to talk technical details, I'll be happy to. As I'm
sure will the other ET enthusiasts...

Tom

--
Definition of Loop: See Definition of Loop

========
Newsgroups: sci.space.policy,sci.space.tech,sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: maury@remove_this.istar.ca (Maury Markowitz)
Date: Wed, 10 Mar 1999 17:16:29 GMT
Cc: t_moore@bellsouth.net

In <36E5E51F.9E341DF8@bellsouth.net> Thomas Moore wrote:
> As someone else already mentioned today, Hilton Hotels seems to be
> interested in a ET based space hotel. I have broken the thread out
> seperately. For those who haven't read the article, it can be found at:

All experiments on keeping the ET in space, and ET-cargo-pannier ideas
were killed off post Challenger and I don't believe they have been looked
at since. I know they're doing porting of the fuel via an intertank valve
now (actually always the case, no?) but without the ability to dump the
fuel via the main engines which was the "solution" to the problem in the
past. The result is that the ET ends up with extra fuel inside, and not
all of it is vented. The safety of the tanks after repeated warming
presurizes the interior is in doubt. This isn't simply a case of making it
hard to get the manholes off or such, the tanks could rupture.

Moreover the tools to get the manhole covers off have not been looked at,
and I don't think they even exist, nor do I know if the manholes are even
installed any more. This isn't as easy as they make it sound, there are
some very serious safety and construction problems that need to be looked
at.

Maury

========
To: sci-space-tech@moderators.uu.net
To: maury@istar.ca
Newsgroups: sci.space.policy,sci.space.tech,sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: Thomas Moore <t_moore@bellsouth.net>
Date: Wed, 10 Mar 1999 22:11:53 GMT

Maury,
I assume your statement of all experiments being canceled post Challenger
is referring to NASA. Quite obviously there are a number of people who still
look at the concepts and explore the technical aspects.

Now obviously we aren't talking about using a stock tank. Any ET station
design regardless of the complexity would require at least some minimal changes
to the ET tanks. Adding a "Venting" capability is one of the options that
would definately have to be explored. Returning to the venting through the
engines concept is not ruled out.

As for the repeated warming pressurizations? Well personally in my viewpoint,
the tanks would be vented shortly after attaining orbit. This would eliminate
the pressurization issue. Granted you lose all that H2 and O2, but if the
studies showed that your concern on the pressurization is a major problem,
losing the H2 and O2 is a minor price to pay to gain the empty volume.

As for tools to get the manhole covers off? Thats a very minor an issue. If
you can come up with a tool to put the things on, I promise you that engineers
can design 100 tools to take the covers off. I am reasonably certain the
manholes are still installed. Those manholes allow access to the tanks after
they are built for final inspection among other things. Eliminating that
inspection would be a serious safety issue.

Are there technical problems with using ET's for station components?

You bet there are. But half the fun of considering the concept is attempting
to solve those problems. Or at least it is for me. Take the design in my
story. One of the commonly considered problems of ET stations is how to
connect the H2 and O2 tanks. Most designs up to now want to put a tunnel in
the Intertank. I personally don't like that idea. There are a lot of
structural load issues when you start messing with that part. So instead, I
toss the intertank and stick a Unity syle node between the H2 and O2 tanks. By
doing so, I avoid having to redesign the structural load characterizistics of
the intertank. I lose only a small amount of volume from the intertank,
(remember, the H2 fore dome and O2 aft dome are inside the intertank... they
take up a lot of space). So what did I accomplish? Well I reduced the cost of
the ET modification, avoided major design changes, and that node gives me a
docking location as well as a "construction shack" for working on the tank
interiors, as well as more volume then the intertank could have supplied. From
a business standpoint for financing a station of this type, I could make a
pretty good case for my concept on those points alone.

Tom

--
Definition of Loop: See Definition of Loop

========
Newsgroups: sci.space.policy,sci.space.tech,sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: gbaikie@my-dejanews.com
Date: Thu, 11 Mar 1999 00:20:22 GMT

I have a wild idea (aren't you glad); why just take the Oxygen tank? Using
heat explosives "cut" this section off, and bring it up to ISS and use as
storage. -gb

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: rx7drivr@aol.com (RX7drivr)
Date: 11 Mar 1999 10:22:37 GMT

>This isn't simply a case of making it
hard to get the manholes off or such, the tanks could rupture.

I have a solution.
Take an ET into orbit instead of letting it reenter.. Wait 6 months. See if
it ruptures or not.
James

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Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: "Greg Moore (Strider)" <mooregr@greenms.com>
Date: Fri, 12 Mar 1999 19:57:37 -0500

And if it does, you've just created one of the largest threats to LEO
bodies imaginable.

That would make it virtually impossible to launch another shuttle
flight.

--
Greg D. Moore President mooregr@greenms.com
Green Mountain Software http://www.greenms.com/
518-283-4083 MCSE

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: gherbert@crl3.crl.com (George Herbert)
Date: 13 Mar 1999 13:32:48 -0800

>> >This isn't simply a case of making it
>> hard to get the manholes off or such, the tanks could rupture.

It's not going to rupture. The LOX and LH feed lines are open to space
and will relieve pressure, once you disconnect it from the shuttle.

[Any ET->station conversion also has to include plates to seal those
feed lines...]

-george william herbert
Retro Aerospace
gherbert@retro.com gherbert@crl.com

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: Mike Dicenso <mdicenso@seds.lpl.arizona.edu>
Date: Thu, 18 Mar 1999 14:48:56 -0700

On Fri, 12 Mar 1999, Greg Moore (Strider) wrote:
> And if it does, you've just created one of the largest threats to LEO
> bodies imaginable.

Even before then, the ET would be shedding the foam insultation for at
least a couple of weeks because of exposure to atomic oxygen, and hard UV
radiation. There'll be a nice big expanding cloud of debris coming off the
ET. Depending on the altitude, the debris might reenter in a couple of
weeks because of the relative light-weight nature of the foam (of course
they said the same about the HST solar array wing too), or it could take
months. So you don't need the tanks to rupture just to create a debris
hazard from an ET.
-Mike

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: "John Stanley" <thestanleys@datastar.net>
Date: Thu, 18 Mar 1999 19:18:37 -0600

Sorry I didn't see this thread from the start but heres my 2 cents. The ET
will not, I repeat will not rupture. The ET serves as the backbone of the
entire STS. It absorbs and distributes all the loads generated during
launch and flight by the three orbiter main engines and the SRBs. I must
also mention that the loads this structure encounters during Proof test
during the manufacturing process exceed those experienced during flight.

There have been and still are concepts that utilize an expended ET in space.
Some examples are using the residual hydrogen and oxidizer as fuel or
environment gases for the Space Station. Docking an ET in the Station
complex and offloading fuel, water, etc into it (sort of like an on orbit
storage tank.) There have been thoughts of using the vast interior of the
ET for many other things.

As far as the foam posing a debris hazard I don't really think this is
a concern. The foam sees far harsher environments during launch and
flight than it would ever see in space. Speeds as low as 10,000 miles
per hour in thin atmospheres generates enormous aero-loads and
aero-heating. The temperature extremes (cryogenics inside & extremely
high temperature on the outside) are a rigorous test of this material
and the process that applies it. I have seen high altitude videos of
an ET re-entering the atmosphere. Should you get the opportunity to
view this video I'm sure you would not concern yourself with bits of
foam bothering us here on Good Planet Earth. The potential for damage
to LEO objects due to debris from an orbiting ET is extremely remote.
There just happens to be tons of junk up there right not that carries
a lot more mass than foam with a density of 2.5 lbs/cubic foot.

We already have the technology and equipment necessary to remove the
Manhole covers and other access port covers in space should we desire
to do so. I guess the bottom line is that this vehicle is a complex
and extemely robust piece of hardware. I'm certain that we will
eventually devise a plan to utilize its tremendous size and strength
even after it has served its purpose of moving humans safely into the
harsh enviorment of outer space. Again that's just my 2 cents.

John

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: Mike Dicenso <mdicenso@seds.lpl.arizona.edu>
Date: Fri, 19 Mar 1999 13:34:54 -0700

On Thu, 18 Mar 1999, John Stanley wrote:

> The ET will not, I repeat will not rupture. The ET serves as the
> backbone of the entire STS. It absorbs and distributes all the
> loads generated during launch and flight by the three orbiter main
> engines and the SRBs.

Err that's all well, and good. But just because the ET is able to handle
the loads imparted to it during launch, does not mean it will not rupture
at some point after it has been left in orbit. There are numerous
documented cases of rocket stages (essentially tanks) exploding on orbit
after sometimes spending years on-orbit. The only reason the STS ET
would'nt suffer such a catastropic failure is because of the open LOX/LH
disconect valves vent propellent overboard after seperation from the
orbiter.

> Some examples are using the residual hydrogen...

There are all kinds of ideas floating around out there, but many of them
require extensive modifications to the ET equal to, or greater than those
implimented for the SLW-ET now entering service. A more intelligent use of
the ET would be just to take the Skylab route, and fully outfit the LH
tank into a space station on the ground.

> As far as the foam posing a debris hazard I don't really think this
> is a concern. The foam sees far harsher environments during launch
> and flight than it would ever see in space.

Really? So they expose the ET insulation to atomic oxygen on a regular
basis? ET insulation has had a history throughout the program of coming
off during launch, and contributing to thermal tile damage (The most
recent example being STS-91, the first flight of an SLW-ET).

> Speeds as low as 10,000 miles per hour in thin atmospheres generates
> enormous aero-loads and aero-heating. The temperature extremes
> (cryogenics inside & extremely high temperature on the outside) are
> a rigorous test of this material and the process that applies it.

So do the shuttle thermal tiles, and blankets, yet the tiles are so
fragile that I can gouge them with my fingernail. There are plenty of
things that can destroy, or damage the ET insulation without having to
subject it to high speeds, or temperature extremes. Atomic oxygen is one
potenially destructive element found in space (on the ground it's
handling accidents, and woodpeckers).

> I have seen high altitude videos of an ET re-entering the
> atmosphere. Should you get the opportunity to view this video I'm
> sure you would not concern yourself with bits of foam bothering us
> here on Good Planet Earth.

That isn't a concern because the insulation foam wasn't intended to
survive reentry like that. The reentry of ET debris IS a problem if your
going sail a boat under the ET debris impact footprint in the Pacific.

> The potential for damage to LEO objects due to debris from an
> orbiting ET is extremely remote.

Somewhat true, the problem is getting worse over time, and is expected to
continue to get worse. So much so that numerous changes were made to the
ISS' debris shield system, and the shuttle radiators and TPS is being
modified to withstand impacts better. Having an ET add to the problem by
shedding it's insulation on orbit only aggravates a steadily increasing
problem.

> There just happens to be tons of junk up there right not that
> carries a lot more mass than foam with a density of 2.5 lbs/cubic foot.

A chunk of foam hitting hitting you, or a satellite can still have
enough KE to kill, or damage just as surely as if you took a gun, or
hand grenade to it. If there is a cloud of little bits of the stuff it can
also be a potential contamination source as well.

> We already have the technology and equipment necessary to remove the
> Manhole covers and other access port covers in space should we
> desire to do so.

The access ports are'nt big enough to move large items through, like the
ISS ISPERs racks either. Redesigning the ET to have large airlock hatches,
and such substantially changes the ballgame since cutting huge holes in
tankage changes the structural integrity (as per what happened to Node 2).
Cutting holes, and installing hatches on orbit presents whole new
problems.

> and strength even after it has served its purpose of moving humans safely
> into the harsh enviorment of outer space. Again that's just my 2 cents.

Your welcome to them. But solving the problems of putting an ET into orbit
is'nt just as simple as some folks would like to have us believe either.
-Mike

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: "John Stanley" <thestanleys@datastar.net>
Date: Fri, 19 Mar 1999 20:47:22 -0600

Well it appears I've upset someone. My intent was to simply provide some
information about a subject (The ET) that I have considerable experience
with. (23 years to be exact). If you took my comments as a personal assult
I do apologize. It was not my intent. I won't get into an online debate
about the subject it serves no worthy purpose. Suffice it to say that I'm
very comfortable with regards to the accuracy of the information contained
in the post. Please pardon my intrusion.

John

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: "Jorge R. Frank" <jrfrank@ibm-pc.org>
Date: Fri, 19 Mar 1999 21:29:00 -0600

> Please pardon my intrusion.

No - please feel free to contribute your experience. My one bone to
pick is your belief that shedded ET insulation will not pose an orbital
debris hazard. This is true - but only for spacecraft launched into the
same orbit as the ET. Spacecraft in other orbits - including those with
identical inclination but different RAANs - will encounter the ET
insulation at high relative velocities. This will present a hazard to
the spacecraft regardless of the "softness" of the ET insulation.
Recall the pitting to the shuttle windows on a past flight caused by a
microscopic paint flake.
--

JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" and think one step ahead of IBM.

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: Mike Dicenso <mdicenso@seds.lpl.arizona.edu>
Date: Sat, 20 Mar 1999 13:22:51 -0700

On Fri, 19 Mar 1999, Jorge R. Frank wrote:
> the spacecraft regardless of the "softness" of the ET insulation.
> Recall the pitting to the shuttle windows on a past flight caused by a
> microscopic paint flake.

Excellent example Jorge! That happened to Challenger on STS-7 didn't it?
There have also been the debris strike on Salyut, and Mir as well as I
recall.
-Mike

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: gbaikie@my-dejanews.com
Date: Sun, 21 Mar 1999 03:57:22 GMT

> Recall the pitting to the shuttle windows on a past flight caused by a
> microscopic paint flake.

Curious. How did they determine it was a paint flake, or was this simply a
guess?
-gb

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: "Jorge R. Frank" <jrfrank@ibm-pc.org>
Date: Sat, 20 Mar 1999 22:34:27 -0600

They analyzed the residue left in the pit in the window.

--

JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" and think one step ahead of IBM.

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: henry@spsystems.net (Henry Spencer)
Date: Sun, 21 Mar 1999 05:16:55 GMT

>Curious. How did they determine it was a paint flake, or was this simply a
>guess?

Traces of the impacting object remained in the little crater.
--
The good old days | Henry Spencer henry@spsystems.net
weren't. | (aka henry@zoo.toronto.edu)

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: gbaikie@my-dejanews.com
Date: Sun, 21 Mar 1999 23:47:18 GMT

> Traces of the impacting object remained in the little crater.

I'm trying to get idea of how much this was studied, so I hope I'm not
sounding like a troll. Was the shuttle window removed because it was badly
damaged, and therefore could be studied in detail, or were the traces scraped
off and put in a sample container? Paint is made of various oxides- pigment
and binding agents. It seems like if they really studied this, they could
determine the paint manufacture, and perhaps where the paint came from. It
seems to me that debris from say a 51 inclination shouldn't impact with very
much of speed vehicles in the same inclination- in other words ISS debris
wouldn't impact itself and that the speed of debris would depend largely on
the needed delta-v to get to a different inclination. Therefore you would
have different impact speeds which are knowable for various inclination and
this also could identify where the paint chip came from. -gb

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: Mike Dicenso <mdicenso@seds.lpl.arizona.edu>
Date: Sat, 20 Mar 1999 13:18:05 -0700

On Fri, 19 Mar 1999, John Stanley wrote:
> Well it appears I've upset someone.
Not at all!

> My intent was to simply provide some information about a subject
> (The ET) that I have considerable experience with. (23 years to be
> exact).

Does that mean actually working on the construction, or launch prep?
In many respects, some us involved in these debates have quite a bit of
experiance/knowledge were ETs are concerned, even if we've never worked
with them directly.

> I do apologize. It was not my intent. I won't get into an online debate
> about the subject it serves no worthy purpose.

No need, although I think it might be a good idea in the future to follow
the debate, or Deja News before getting involved. Much of the info covered
has already been brought up before, and answered in past debates.

> Suffice it to say that I'm very comfortable with regards to the
> accuracy of the information contained in the post. Please pardon my
> intrusion.

There's plenty of concerns about the usage of unmodified ETs on-orbit even
without the potential problem of a tank rupturing. The debris issue is
just one to be sure, but there is also the problem of just randomly
putting ETs up into different orbits every time without the benefit of GNC
of some sort (talk about Skylab revisited!).

-Mike

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: "John Stanley" <thestanleys@datastar.net>
Date: Sun, 21 Mar 1999 17:19:11 -0600

>Does that mean actually working on the construction, or launch prep?
>In many respects, some us involved in these debates have quite a bit of
>experiance/knowledge were ETs are concerned, even if we've never worked
>with them directly.

Manufacture and Test of the ET since 1976.

John

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: tabbott@intellex.com (Tom Abbott)
Date: Sun, 21 Mar 1999 22:05:40 GMT

On Fri, 19 Mar 1999 13:34:54 -0700, Mike Dicenso
<mdicenso@seds.lpl.arizona.edu> wrote:

>There are all kinds of ideas floating around out there, but many of them
>require extensive modifications to the ET equal to, or greater than those
>implimented for the SLW-ET now entering service. A more intelligent use of
>the ET would be just to take the Skylab route, and fully outfit the LH
>tank into a space station on the ground.

I like the way you think, Mike! :)

>> We already have the technology and equipment necessary to remove
>> the Manhole covers and other access port covers in space should we
>> desire to do so.

>The access ports aren't big enough to move large items through, like the
>ISS ISPERs racks either.

The standard ET access ports are 36 inches wide. ISS's access ports
are 44 inches(?). Astronauts have already demonstrated, in NASA's
underwater facility, that they can unbolt the ET's access doors and
pass back and forth freely while in spacesuits.

> Redesigning the ET to have large airlock hatches, and such
> substantially changes the ballgame since cutting huge holes in
> tankage changes the structural integrity (as per what happened to
> Node 2).

The 1995 NASA Geode External Tank space station had a very large
airlock (7.5 feet wide) cut into the ET oxygen tank before launch.
Here's what the Geode "Disclosure of Invention" has to say about the
modifications to the oxygen tank:

"The actual scarring of the External Tank for on-orbit utilization
has been reviewed by MMC/MAF and is regarded as achievable and
realistic, while also causing minimal impact to NSTS 07700, Vol X. In
an overview perspective, it entails utilizing the single-radius wall
of the barrel section of the LO2 tank (approx. 8.5 ft high). A
"double door/wall" has been proposed that would satisfy Ascent Design
requirments as well as those of related Ops Scenarios while on-orbit.
This configuration would be similar to the existing inspection plates
(manhole covers) located in both the LO2 and LH2 aft tank domes. The
main excursion from the certified design would be the introduction of
an inner door/plate that would serve as the primary cryogenic seal and
an outer cover that would be conformal to the ET outer moldline and
incorporate appropriate deployment schemes utilizing the Orbiter RMS.
Under the outer cover plate would be the Adapter Collar seal & attach
surface with integrated hardware for RMS docking of the unit. LO2
tank ullage volume and characteristics are anticipated to receive
minimal impact from the introduction of this hardware into the barrel
section and slosh baffles. Loads will be distributed through an
annulus compression ring, effectively isolating the 7.5 ft diameter
scarring from ascent loads."

>Cutting holes, and installing hatches on orbit presents whole new
>problems.

True.

>> and strength even after it has served its purpose of moving humans safely
>> into the harsh enviorment of outer space. Again that's just my 2 cents.

>Your welcome to them. But solving the problems of putting an ET into orbit
>isn't just as simple as some folks would like to have us believe either.
>-Mike

And, of course, it is not as hard as some others would have us
believe. Somewhere in the middle is about right.

TA

========
Newsgroups: sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: tabbott@intellex.com (Tom Abbott)
Date: Sun, 21 Mar 1999 21:19:52 GMT

On Thu, 18 Mar 1999 14:48:56 -0700, Mike Dicenso
<mdicenso@seds.lpl.arizona.edu> wrote:
> Even before then, the ET would be shedding the foam insultation for at
> least a couple of weeks because of exposure to atomic oxygen, and hard UV
> radiation. There'll be a nice big expanding cloud of debris coming off the
> ET.

I'm told by several people who ought to know that the ET's insulation
will not shed as described, because of some new process which
supposedly prevents this. I have no details on the specifics, but
that's what I've been told. Even if shedding is a problem, it can be
fixed fairly easily by using a defocused electronbeamgun to remove the
SOFI from the ET. An automated electrobeamgun could cover the entire
ET in a matter of a few days.

> Depending on the altitude, the debris might reenter in a couple of
> weeks because of the relative light-weight nature of the foam (of
> course they said the same about the HST solar array wing too), or it
> could take months. So you don't need the tanks to rupture just to
> create a debris hazard from an ET.

If the ET were held at a 175 mile altitude while the SOFI was removed,
the SOFI would deorbit in a matter of days.

TA

========
To: sci-space-tech@moderators.uu.net
Newsgroups: sci.space.policy,sci.space.tech,sci.space.shuttle
Subject: Re: External Tanks, Space Hotels, and Roton.
From: "Claude J. Lemelin" <clemelin@***NO_SPAM***netc.net>
Date: Wed, 10 Mar 1999 20:40:57 -0500

Hi,

Just to add to the discussion there is some ET space station design that
have been propose at the tenth Princeton/AIAA/ Space Study Institute
Conference (May 15-18, 1991). You can find these papers in the conference
proceedings

Space Manufacturing 8 Energy and Materials from Space published by AIAA
ISBN1-56347-022-5

See you

Diphda

========
To: sci-space-tech@moderators.uu.net
To: Rodent <rodent@thinkthink.com>
Newsgroups: sci.space.tech,sci.space.sci
Subject: Re: STS ET Re-use Questions
From: Tom <t2jr@bellsouth.net>
Date: Wed, 17 Mar 1999 02:40:03 GMT

Rodent wrote:

> #1. If STS ET is brought into orbit, would the tank rupture due to
> solar heating of the propellant?

There are pressure relief valves (See 3)

> #2. If so, how long until one or both tanks rupture?

Until a meteoroid or debris hits it.

> #3. Does the STS ET purposefully vent before deorbit?

The propellant lines are open to space and so vent continuously.

> #4. Conduits from STS ET to SSME are closed using a spring
> loaded device activated by explosive bolts. Can these valves
> be reopened without a redesign?

Probably not. The SSME's would need redesign to re-ignite however.

> #5. Could the LH and LOX be combined into water using a
> combustion chamber similar to an internal combustion engine
> (either piston or turbofan) and the power stored?
> **side note**

The SIVB had an O2/H2 burner to pressurize / heat the tank ullage gas.
However, solar is more efficient if you're talking about power
generation.

> I'm sure this could not be done inside the ET, but an OTV could
> perform the operation. I do know that the SSME's run hydrogen
> rich, so there would be be excess hydrogen. I considered running

They run rich for higher Isp due to the improved average molecular
weight resulting in a higher energy usage for a limited expansion ratio.

> the H and O through a fuel cell (or bank of them), but thought it
> would be to time consuming especially if solar thermal heating is
> a major factor. I know that a substantial thermal radiator would be
> needed for the heat involved with the ICE. This could come in
> handy for keeping the excess H at liquid temperature and possibly
> the ET residual fuel at cryogenic temp before processing.
> IMHO, Converting the H and O to water would be much more
> stable than trying to keep them separately in orbit.

More efficient to just loft the mass as water and use the full ET
capacity for propulsion.

> #6. It was my understanding that the hydrogen tank walls
> where too thin to be used for 14.7 lb pressure. Am I wrong
> in this assumption?

The H2 tanks operate at 33 psi and the O2 at 21 psi.

> #7. If so, could the hydrogen tank be used as a low pressure
> work shroud? Meaning, if the pressure could be brought to
> 2, 5 or even 10 psi, lighter, more flexible EVA suits could
> be used. Waste products such as unprocessable urine brine,
> dehydrated fecal matter, or even discard able equipment could
> be stored.

WAY too big a tank for that use. The drag makeup propellant alone would
eat up the extra propellant margin.

> #8. If the weight of the tank (including residual propellant) was
> counted as cargo, what would the launch $'s per lb be?

The tank is 66,021 lb. Residual propellant runs 10,000 to 15,000 lb.

> #9. Recently, Delta launches have had externally mounted cameras
> that transmit the ascent and orbital insertion. Could the STS ET be
> equipped with a number of these type of cameras to record the
> behavior of an ET when brought into orbit.

========
To: sci-space-tech@moderators.isc.org
Newsgroups: sci.space.tech
Subject: Re: STS ET Re-use Questions
From: "tdbear" <tdbear@mpx.com.au>
Date: Thu, 18 Mar 1999 15:15:49 +1100

Dear 'Rodent',

I can only provide a couple of suggestions to your questions. Please read
them.

Rodent wrote in message <36ED9545.C9262616@thinkthink.com>...
> #1. If STS ET is brought into orbit, would the tank rupture due to
> solar heating of the propellant?
>
> #2. If so, how long until one or both tanks rupture?
>
> #3. Does the STS ET purposefully vent before deorbit?

Yes, in order to break the tank up before it reaches the ocean, the
excess oxygen is vented to cause the tank to tumble. This increases
the aerodynamic and thermodynamic loads.

> #4. Conduits from STS ET to SSME are closed using a spring
> loaded device activated by explosive bolts. Can these valves
> be reopened without a redesign?
>
> #5. Could the LH and LOX be combined into water using a
> combustion chamber similar to an internal combustion engine
> (either piston or turbofan) and the power stored?

A combustion engine would burn the propellants, leaving you with heat,
vibration and not much else. A better idea would be to use fuel cells
like the ones on the Space shuttle. The problem might be the amount
of residual propellant in the tanks.

I remind you, however, that the tank weighs in the order of 30 tonnes
(The original tank weighed in the order of 33.5 tonnes). It is too
heavy for the Shuttle to take into Earth orbit. The Shuttle payload
is in the order of 21-23 tonnes.

> **side note**
> I'm sure this could not be done inside the ET, but an OTV could
> perform the operation. I do know that the SSME's run hydrogen
> rich, so there would be be excess hydrogen. I considered running
> the H and O through a fuel cell (or bank of them), but thought it
> would be to time consuming especially if solar thermal heating is
> a major factor. I know that a substantial thermal radiator would be
> needed for the heat involved with the ICE. This could come in
> handy for keeping the excess H at liquid temperature and possibly
> the ET residual fuel at cryogenic temp before processing.
> IMHO, Converting the H and O to water would be much more
> stable than trying to keep them separately in orbit.
>
> #6. It was my understanding that the hydrogen tank walls
> where too thin to be used for 14.7 lb pressure. Am I wrong
> in this assumption?
>
> #7. If so, could the hydrogen tank be used as a low pressure
> work shroud? Meaning, if the pressure could be brought to
> 2, 5 or even 10 psi, lighter, more flexible EVA suits could
> be used. Waste products such as unprocessable urine brine,
> dehydrated fecal matter, or even discard able equipment could
> be stored.
>
> #8. If the weight of the tank (including residual propellant) was
> counted as cargo, what would the launch $'s per lb be?
>
> #9. Recently, Delta launches have had externally mounted
> cameras that transmit the ascent and orbital insertion. Could
> the STS ET be equipped with a number of these type of
> cameras to record the behavior of an ET when brought
> into orbit.
> **side note**
> I'm sure NASA would seriously consider a proposal of
> this fashion. Possibly stirring interest in ET re-use once again.
> Any opinions on this?

To take the ET into orbit would require an additional booster of some sort.
In the days before the Challenger explosion, NASA seriously proposed using a
re-packaged Titan stage to increase the Shuttle's payload into orbit. I'm
not sure if the ET structure would be strong enough to handle the extra
load.

> --
> rodent (putting the eek in geek)
> <A HREF="mailto:rodent@thinkthink.com">
> ---------------------------
> Stop throwing away everything, ANY mass
> put in orbit is worth more than gold.

========
To: sci-space-tech@moderators.uu.net
Newsgroups: sci.space.tech
Subject: Re: STS ET Re-use Questions
From: Tom <t2jr@bellsouth.net>
Date: Sat, 20 Mar 1999 00:59:46 GMT

tdbear wrote:
>
> Dear 'Rodent',
>
> I can only provide a couple of suggestions to your questions. Please read
> them.
>
>
> I remind you, however, that the tank weighs in the order of 30 tonnes (The
> original tank weighed in the order of 33.5 tonnes). It is too heavy for the
> Shuttle to take into Earth orbit. The Shuttle payload is in the order of
> 21-23 tonnes.
>
> To take the ET into orbit would require an additional booster of some sort.
> In the days before the Challenger explosion, NASA seriously proposed using a
> re-packaged Titan stage to increase the Shuttle's payload into orbit. I'm
> not sure if the ET structure would be strong enough to handle the extra
> load.

This is not correct. The ET is already *ALMOST* in orbit. It weighs
66,000 lbs but the Orbiter weighs up to 248,000 lbs and places itself
in orbit easily. The orbiter carries 25,000 lbs of OMS propellant. At
MECO, the Orbiter/ET is in a 60 x 160 to 60 x 330 nmi orbit depending
on final destination. There's enough OMS fuel to get the orbiter to
330 nmi so the Orbiter could put an ET as high as 250 nmi or so.
Higher if you use a descent tether. (Tie a tether to the ET. Spool out
the tether to about 600 miles. This lowers the Orbiter by 120 nmi and
raises the ET by 480 nmi. Cut the tether and the orbiter drops to a
130 x 10 nmi reentry orbit but the ET gets slung to a 730 x 1210 nmi
orbit.

========
To: sci-space-tech@moderators.uu.net
Newsgroups: sci.space.tech
Subject: Re: STS ET Re-use Questions
From: "Jorge R. Frank" <jrfrank@ibm-pc.org>
Date: Fri, 19 Mar 1999 22:18:19 -0600

tdbear wrote:
> I remind you, however, that the tank weighs in the order of 30
> tonnes (The original tank weighed in the order of 33.5 tonnes). It
> is too heavy for the Shuttle to take into Earth orbit. The Shuttle
> payload is in the order of 21-23 tonnes.

<snip>

> To take the ET into orbit would require an additional booster of
> some sort. In the days before the Challenger explosion, NASA
> seriously proposed using a re-packaged Titan stage to increase the
> Shuttle's payload into orbit. I'm not sure if the ET structure
> would be strong enough to handle the extra load.

It's not quite that bad. The shuttle currently carries the ET all the
way through powered ascent. For today's direct-insertion ascents, all
that would be required to put an ET in orbit would be for the the
shuttle to delay ET SEP until after the OMS-2 burn. The extra weight of
the ET would increase the propellant cost of OMS-2 by 1000-4000 lbm
(depending on OMS-2 altitude and orbit ellipticity), but it would not
require an extra booster.

Now, *keeping* an ET in orbit once an orbiter has deposited it there is
a different story...

--

JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" and think one step ahead of IBM.

========
Newsgroups: sci.space.tech
Subject: Re: STS ET Re-use Questions
From: navigaiter@aol.com (Navigaiter)
Date: 19 Mar 1999 07:10:19 GMT

> #8. If the weight of the tank (including residual propellant) was
> counted as cargo, what would the launch $'s per lb be? ...
> I'm sure NASA would seriously consider a proposal of this
> fashion. Possibly stirring interest in ET re-use once again. Any
> opinions on this?

Assuming my connecting your two statements is appropriate, it would
seem that NASA would be interested in posting an attractive cost/pound
to orbit figure which delivering an ET to orbit would offer.

The challenge is partly to interest investors in owning an orbiting
set of tanks. Us space enthusiasts know that that orbital property
will have *tremendous* value in time. Better than aol stock ;-)

If NASA were able to apply common sense, they would try auctioning the
delivered tanks. But they don't because there are political, strategic
and security issues around selling government surplus equipment
located in such an important place as earth orbit.

Space enthusiasts must lose their naivetee about the reasons for the
seemingly stupid waste of taxpayers' expensive ET's. Then they may
fight the real demon -- politics.