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Date: Fri, 29 Mar 91 01:47:21 -0500 (EST)
Subject: SPACE Digest V13 #317

SPACE Digest                                     Volume 13 : Issue 317

Today's Topics:
	     Re: railguns and electro-magnetic launchers
	       Space Station Plan Completed (Forwarded)
			    Re: "Follies"

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----------------------------------------------------------------------

Date: 21 Mar 91 08:08:55 GMT
From: snorkelwacker.mit.edu!stanford.edu!leland.Stanford.EDU!zowie@apple.com  (Craig DeForest)
Subject: Re: railguns and electro-magnetic launchers

prentice@triton.unm.edu (John Prentice) writes:
>henry@zoo.toronto.edu (Henry Spencer) writes:
>>prentice@triton.unm.edu (John Prentice) writes:
>>>I thought the real problem was surviving the initial acceleration...
>>mumble radar proximity fuzes in WW2 mumble Project HARP.
>EM launchers involve accelerations many orders of magnitude larger than 
>chemical guns (or even light gas guns).  I have seen some railguns push 
>100 g's in weapons tests.  ... Does anyone
>know what accelerations are involved?

Let's do a back-of-the-terminal calculation [gee, actually *THINK*?
on USENET?  Flame him to death!]

Lesse: the bullet of a `typical' hunting rifle comes out at the
speed of sound, after accelerating from rest inside the (1m) barrel.
Assume constant acceleration:
	a = v^2 / d = (300m/s)^2 / 1m = 10^5 m/s^2 = 10^4 g's!
This is clearly much larger than the largest railgun acceleration you saw.
Are you sure you meant 100 g's and not 100 kilo-g's?

In fact, an arrow goes about 70 m/s, and got there in about 0.5m; so
the bow-and-arrow combination does about 1000 g's!  This is still an
order of magnitude greater acceleration than your railgun! Are you
*sure* you meant 100 g's and not 100 kilo-g's?  [Sanity check: ya pull
about 70#; an arrow weighs about an ounce -- that's about a thousand
g's, allright] This is an interesting comment on material strength:
arrows are typically light wood (pine?) or sheet metal or plastic,
with flimsy plastic or real feathers at the back.  All of these
materials withstand the initial (and much stronger final) acceleration
in the arrow!

For an EM launcher, we want (about) 10km/sec, in (say) 100m.  This is
	( 10^8 / 10^2 ) m/s^2 = 10^5 g's
which is an order of magnitude above the acceleration in the `typical' 
hunting rifle, but roughly *equal* to the acceleration in a `high-powered'
hunting rifle with exit speed 1000 m/s.

A 10m launcher (about as high as a five-story dormitory) would take
10^6 g's, a clear order-of-magnitude increase over the `high-powered'
hunting rifle.  Ouch!  We'll probably need a long launcher.

Since the acceleration scales as the *square* of the exit velocity, the
100m EM launcher could be used as the (most fuel-intensive!) first boost
in a multi-stage launch.  If we only wanted to go 1km/s, we would only
undergo the same paltry ( :-) ) 1000 g's as a pinewood arrow!  

Can we make precision instrumentation that can undergo 1000 g's?  This 
question will have to wait: my shockproof Timex says it's time to go... :)

-- 
When thinking is outlawed, only   |  Craig DeForest
criminals will have brains!       |     zowie@banneker.stanford.edu 
                 DON'T DRINK SOAP! DILUTE! DILUTE! OK!

------------------------------

Date: 21 Mar 91 17:02:52 GMT
From: agate!bionet!uwm.edu!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@ucbvax.Berkeley.EDU  (Ron Baalke)
Subject: Space Station Plan Completed (Forwarded)


Mark Hess
Headquarters, Washington, D.C.                                  March 21, 1991
(Phone:  202/453-4164)

RELEASE:  91-45

SPACE STATION FREEDOM RESTRUCTURING PLAN COMPLETED

	NASA today delivered the "restructuring" report to the Congress,
outlining an extensive redesign of the Freedom space station.  The new design
is cheaper, smaller, easier to assemble in orbit and will require fewer Shuttle
flights to build.

	Major new features of the redesigned space station - shorter U.S.
laboratory and habitat modules that can be outfitted and verified on the ground
and a pre-integrated truss that can be assembled on the ground and tested with
all of its subsystems intact - will significantly reduce intravehicular
activity (IVA) and on-orbit extravehicular activity (EVA) needed to build and
maintain Freedom.

	"This new design for Space Station Freedom accomplishes every major
goal we set for ourselves when we kicked off this effort last November," said
William B. Lenoir, Associate Administrator for Space Flight.  "We took the
directions from Congress and the Augustine Commission recommendations to heart,
and the program we are announcing today addresses each and every one of their
requirements.

	"We've cut costs, simplified the design and reduced the complexity of
the project.  At the same time, Freedom will be a quality facility, providing a
research laboratory unsurpassed in the world for life sciences and microgravity
research, and a stepping stone into the future, enabling NASA to conduct the
research and planning necessary for human exploration of the solar system.  And,
we have maintained our international commitments," he continued.

	A 1991 fiscal year budget shortfall of more than $550 million, along
with Congressional directions to significantly reduce out-year spending,
prompted NASA to begin the restructuring of Freedom.  Congress told NASA to
expect no more than 8 to 10 percent growth over the next 5 years
(FY 1992-1996), with peak spending for Freedom not to exceed $2.5-2.6 billion.
The budgetary ground rules, including the cut for FY 1991, represent a $5.7
billion shortfall from what NASA had planned to spend for Freedom over that
same time period.

	NASA directed the review in November 1990 with instructions to the
Freedom project team to:  develop a phased approach with quasi-independent
phases; protect life and materials science; maintain international agreements
and capability; limit assembly flights to no more than four annually; and
achieve first element launch, man-tended capability and permanently manned
capability as early as possible.

	The restructured program calls for the first element launch of the
space station to be made in the second quarter of FY 1996 (January -
March 1996), and man-tended capability to be achieved in the third quarter of
FY 1997 (April-June 1997).

	In the man-tended phase, astronauts brought up to Freedom by the
Space Shuttle will be able to work inside the U.S. laboratory for periods of 2
weeks.  They will return to Earth with the Shuttle.  At this stage, one set of
Freedom's solar arrays will generate about 22 kw of power with a minimum of
11 kw available to users.  Six Shuttle flights will be required to achieve
the man-tended configuration.

	Freedom will achieve a permanently manned configuration in Fiscal Year
2000.  This configuration will consist of the U.S. laboratory and habitat, as
well as the European and Japanese laboratories; the Canadian Mobile Servicing
System; accommodations for a live-in crew of four; and three sets of solar
arrays furnishing 65 kw of electrical power, with a minimum of 30 kw going to
the users and the remainder to housekeeping chores.

	A new requirement before permanently occupying the station will be the
availability of an Assured Crew Return Vehicle to return space station crew
members to the Earth in an emergency.  Seventeen Shuttle flights will be needed
to build the permanently manned configuration.

	Provisions to expand the space station have been maintained.  The
follow-on phase of the Freedom program will include another solar array to
achieve 75 kw, provisions for 4 additional crew members and could include
additional capabilities such as a second preintegrated laboratory and
additional nodes.  This phase would use the new launch system for launch and
assembly if the launch system is available.

	The redesigned U.S. lab and hab modules are 27 feet long and 14.5 feet
in diameter, about 40 percent shorter than the previous design.  The smaller
size allows the modules to be fully outfitted and tested on the ground prior to
being launched into orbit.  The U.S. lab module will hold a total of 24 8-foot
wide racks, 15 of which initially are devoted to scientific work.  At
permanently manned capability, 28 experiment racks will be available to U.S.
investigators: 12 in the U.S. lab, 11 in the ESA lab and 5 in the Japanese lab.

	The redesigned truss segments will be built, preassembled and checked
out on the ground.  Formerly, the truss was to have been assembled, like a
massive erector set, by astronauts performing space walks.  NASA estimates the
pre-integrated truss will cut assembly EVA by more than 50 percent.

	While work on the Attached Payload Accommodations Equipment (APAE)
suitable for large external payloads has been stopped, utility ports for small
external payloads will be placed along the truss.  The overall width of the
station has been reduced from 493 feet to 353 feet.

	Complexity of other station systems also has been reduced and where
possible, hardware already flying on the Space Shuttle will be used in place of
developing new hardware for the station.  Also called for in the plan is the
transfer of the Flight Telerobotic Servicer to NASA's Office of Aeronautics,
Exploration and Technology.  This, together with the deferral of the APAE, has
eliminated the Goddard Space Flight Center's Work Package 3 from the Freedom
program.

	In addition to changes to the flight hardware, a number of changes to
ground facilities are planned.  The Space Station Processing Facility to be
built at the Kennedy Space Center will not be fully outfitted, and a new
hazardous processing facility has been deleted in favor of using an existing
facility.  The size of planned facilities at the Johnson Space Center - the
control center and crew training facilities - have been scaled back.  Payload
facilities at Marshall Space Flight Center are being deferred and existing
facilities will be used in the interim.

	Due to funding cutbacks and hardware changes in the program, some
layoffs of prime and subcontractor personal have already taken place, and more
are expected.  At Work Package 1, no layoffs at the prime contractor, Boeing,
are expected, but more than 500 people will be reduced from the subcontractor
roles, some of which will be accommodated through transfers and attrition.

	At Work Package 2, prime contractor McDonnell Douglas has already
reduced its work force by about 160, with half that number being layoffs.
Major subcontractors to McDonnell Douglas will be reduced by about 470, with
layoffs accounting for approximately half of that, and another 200 will be
reduced from supporting development, with about 65 of that total coming from
terminations.  At Work Package 4, no layoffs are expected, but as many as 40
people in support jobs at Lewis Research Center will be reassigned.  Layoffs
of about 30 percent of the work force at the Space Station Engineering and
Integration Contractor, Grumman, were announced earlier this month.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|      Ron Baalke         | baalke@mars.jpl.nasa.gov
     | | | |  __ \ /| | | |      Jet Propulsion Lab | 
  ___| | | | |__) |/  | | |___   M/S 301-355        | Change is constant. 
 /___| | | |  ___/    | |/__ /|  Pasadena, CA 91109 | 
 |_____|/  |_|/       |_____|/                      |

------------------------------

Date: Wed, 20 Mar 91 10:57:15 -0500
From: "Allen W. Sherzer" <aws@iti.org>
Subject: Re: "Follies"
Newsgroups: sci.space
Cc: 

In article <9103191610.AA11742@cmr.ncsl.nist.gov>:

>>* We need 4 orders of magnitude drop from today's costs for space 
>>  colonization to be affordable.

>There are many types of space colonization possible,
>some of which could get along with significantly higher transportation costs.

A comparison with past efforts is interesting. According to (I think) G.
Harry Stein, both the Plymouth Rock and Salt Lake City colonies where started
with 50 middle to upper middle class famlies selling everything they owned
to pay for the voyage.

Now figure 50 families today with two children and middle to upper income.
At $100K each raised form liquidating their net worth we have $5M. We need to
lift ~750 pounds per family (figure 500 pounds for the people and another
200 pounds for personal effects) for a total of 37.5K pounds. This comes
to $133/pound which is less than two orders from current prices to LEO.

Now they will need to get from LEO to the moon or some L point. However, with
access to lunar resources which will be far cheaper so I figure it rounds off
to under two order reduction. 

Now this approach does assume that there is an infrastructure there to
support the colonists in terms of jobs and resources. However, this can
be provided for in the same way as all other large infrastructure jobs
are done: the government pays for it in anticipation of enough activity later
on to pay for it.

It therefore seems that only about two orders of magnitude are needed.

>ALS
>or the new technology launcher system (with development expected to take about
>a decade, and perhaps as much as 10X reduction in launch costs).

ALS will not achieve an order of magnitude reduction in launch costs. In fact,
I will bet money that it ends up MORE expensive than the Shuttle. This program
will end up as the Space Shuttle of the 90's: lots of money to contractors
few useful results. This program has got to be killed or we will accomplish
nothing in the 90's. Why are we building ALS when we could have better
launchers for 10% the cost and a third of the time?

    Allen

------------------------------

End of SPACE Digest V13 #317
*******************