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basking in its warm rays nature seeks

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this nuclear reactor burns four million

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tons of hydrogen every second creating

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ancient observers worship the

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life-giving rays of this day star

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modern science has taught us to harness

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its power

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this superstar is essential to life on

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earth as well as to one of man's boldest

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ventures

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196 000

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cells will collect energy to power this

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laboratory and indeed become the solar

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the united states

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canada

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japan

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and the european space agency have come

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responsibility for the entire electric

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power system known as work package 4

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rests in cleveland ohio at the nasa

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the power collection system is being

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developed by the solar array branch of

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the photovoltaic power module division

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design of space station began in 1984.

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now its pencils down

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time to build and test the actual flight

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hardware

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in the summer of 1991 for the first time

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anywhere in the world

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an array of cells and structural

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components were tested together in the

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simulated low earth orbit environment of

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tank 5 in the electric propulsion

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funding from nasa's office of safety and

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mission quality and the work package 4

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project office

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allowed engineers to develop and design

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a high-fidelity plasma generation and

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diagnostic system the intent

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to test the electrodynamic reaction

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between the photovoltaic system the

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a nitrogen cold wall was attached to a

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test fixture to regulate temperature of

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the test article

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the cage design allowed for quick

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installation and removal of hardware

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from the vacuum tank

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a light bank of 252 ded lamps was built

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to provide illumination equal to

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one-third of the sun's intensity

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spherical probes measured the current

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voltage profile to determine plasma

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density

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in preparation for the test an engineer

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checks to ensure that illumination is

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falling evenly on each solar cell

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the cells eight millimeters thick and

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eight centimeters square are the largest

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the cells are welded to a flexible

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printed circuit which is insulated from

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the outside environment the cell edges

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sixteen thousand four hundred individual

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cells are grouped into blankets one

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hundred ten feet long by fifteen feet

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wide

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each blanket is protected by and

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deployed from a blanket box

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underwater testing was conducted by

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lockheed corporation aiding engineers in

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improving deployment techniques of the

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from the beginning of life on earth and

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now in space

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nature has relied on the sun

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these sunflower seedlings track the sun

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technology imitates nature

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once freedom's wings are attached to the

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truss alpha and beta gimbals will enable

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them to track the sun during orbit

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60 minutes in sunlight and 30 minutes in

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eclipse

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while in sunlight the six wings will

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collect light and convert it directly to

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electric current

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at the same time 304 nickel hydrogen

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battery cells will be charged to provide

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power while freedom is in earth shade

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up and energized the solar arrays will

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supply more than 56 kilowatts of

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condition power to the user

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the most power ever used in space

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solar energy will supply power for

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experiments

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research projects

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housekeeping functions

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and life support systems

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however these can come crashing to a

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halt in the harsh environment of space

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micrometeors can damage freedom

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structure

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contamination can degrade its power

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and an invisible gas known as plasma can

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cause

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arcing why is that a threat

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the potential effects of such arcing was

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studied by the photovoltaic power module

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division

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project manager marion felder

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the threat that plasma poses to the

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space station freedom was examined here

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in tank 5 during the plasma interactions

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test the objectives of this test were to

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investigate on a systems level the

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possibly detrimental effects of the

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space plasma on the photovoltaic system

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as well as on the structures that make

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up space station freedom

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we also wanted to investigate the

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effectiveness of a possible mitigation

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strategy that is a plasma contactor for

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hardware we used two fully populated

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photovoltaic panels in combination with

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a variety of anodized aluminum

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structures which were there to simulate

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various structures on the space station

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freedom

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the solar ray circuit that we had was

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capable of generating 160 volts at

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almost one amp under test illumination

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conditions we used the voltage that was

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generated on the solar array to drive

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the potential of the aluminum piece to a

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voltage that would be quite close to

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what it would be seeing when on orbit

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the combination of the largest aluminum

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panels and the photovoltaic circuit was

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approximately one four hundred ninety

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the scale of the space station freedom

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and therefore allowed us to get the very

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first large-scale test of plasma

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environment interactions with space

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station type hardware

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our data capture system was designed to

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return information in three specific

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areas current collection floating

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potential and arc transients as well as

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to give us information on key

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environmental parameters like

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temperatures and the plasma potential

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concern for the possible detrimental

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effects of arcing on the space station

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freedom led us to plan and conduct this

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plasma interactions test

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so that the program office could assess

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the risks and develop engineering

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solutions

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we look to the space environment's

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effects branch here at lewis for a more

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detailed description of the low-earth

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orbit plasma environment and its

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contrary to popular belief space station

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freedom will be orbiting not in empty

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space but in the upper reaches of the

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earth's atmosphere the upper reaches of

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the atmosphere are mainly atomic oxygen

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and this atomic oxygen gets ionized by

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the ultraviolet radiation from the sun

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ultraviolet radiation splits the atomic

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oxygen atoms up into an ion and electron

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and in the altitudes the space station

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will be flying there will be something

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like a million electrons and ions per

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cubic centimeter

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that is flying through

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this space plasma as we call it is is

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going to be important in terms of

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interactions between the space station

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and its surroundings

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first of all what what will happen if

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the arcing does occur

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one of the things is it can

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cause tiny holes in the anodized surface

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and change its properties in particular

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could change the thermal properties of

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the surface so that it wouldn't maintain

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the right temperature

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in addition the material that comes off

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during these arcs

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will deposit somewhere else on the space

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station the solution to the possible

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arcing problem on space station we think

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is a device called the plasma contactor

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mike patterson of the space propulsion

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technology division explains his group's

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involvement with the test here at nasa

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lewis at the epl facility tank 5 our

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organization provided support for the

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plasma interactions test for the space

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station freedom solar array one of the

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critical aspects of conducting that

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experiment was to provide a simulation

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of the low earth orbit space plasma

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environment and to do that we provided

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holic acid plasma sources to generate a

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quiescent low density low electron

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temperature space plasma environment we

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used a number of hollow cathode plasma

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source devices

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optimized for operation to provide a low

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electron temperature and a very uniform

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plasma to engulf the solar array to

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simulate the low earth orbit environment

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the plasma contactors have been

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developed previously for specific

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mission applications on specific

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spacecraft primarily for science this is

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really the first time that the plasma

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contactor is going to be used as a

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utility as a technology to ensure that

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the spacecraft can perform its function

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as it turns out it's a vital component

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it will be a vital component of the

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power system aboard space station and

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it's critical for space station

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operations

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so in that in that context it's the

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first time that the technology has

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really been utilized and it's not a

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demonstration of the technology it's

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there to perform a specific function the

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demanding requirements for the plasma

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contactor system for space station

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freedom uh require us to uh

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do everything we can to push the

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holocaustic technology that we presently

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have

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and uh that's a a real challenge for us

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but we'll be able to deliver on that

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one of the important space flight

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experiments for space station is

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what we call sampy

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that's

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solar array module plasma interaction

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experiment

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here at lewis

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it's going to be flown on the space

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shuttle in the year 1994

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and it's being built right now hopefully

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when it flies we'll have confirmation

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in a room much like this lewis will

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monitor the performance of the space

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station's electric power system once on

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orbit

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personal computers such as these are

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used daily to design systems and conduct

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analyses to verify characteristics of

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space station freedom

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soon computers will be used to run the

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machines that fabricate the various

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components

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along with sampi work package 4 plans to

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conduct a qualification type plasma

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interactions test with a flight design

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solar array circuit to confirm the

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operational characteristics of the solar

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arrays in plasma

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work package 4 also plans to take

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advantage of other space flight

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experiments such as pass plus and spear

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3 to gain confidence in the array's

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operation before it flies

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beginning in the mid 90s with the first

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element launch of one photovoltaic power

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module

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and continuing with the remaining

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elements

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space station freedom will be

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constructed in stages to yield a

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permanently manned configuration by the

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end of the decade

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the knowledge that we gain from our

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research in tank 5 will enable