apollo experience report flight-control data needs, terminal display devices and ground system...

8/8/2019 Apollo Experience Report Flight-Control Data Needs, Terminal Display Devices and Ground System Configuration R

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N A S A T E C H N IC A L N O T E N A SA TN 0-7685

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C O P Y

APOLLO EXPERIENCE REPORT -FLIGHT-CONTROL DATA NEEDS,TERMINAL DISPLAY DEVICES,

IREMENTSby Richard A. HooverLyndon B. Johnson spuce CenterHouston, Texus 77058

NAT ION AL AERONAUTICS AN D SPACE ADMIN ISTRATIO N WASHINGTON, D. C. MA Y 1974


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1. Report No. 2. Government Accession No.

APOLLO EXPERIENCE REPORTAND GROUND SYSTEM CONFIGURATION REQUIREMENTSFLIGHT-CONTROL DATA NEEDS, TERMINAL DISPLAY DEVICES,

17. Key Words (Suggested by Author(s) )' Real-Time Operation* Ground-Based Control' Ground Support Equipment' nflight MonitoringConsoles ' Computer-Driven Television

7. Author is)Richard A. Hoover, JSC

18. Distr ibu tion StatementSubject Category 31

9. Perform ing Organiza tion Name and AddressLyndon B. Johnson Space Cente rHouston, Texas 77058

19. S ecuri ty Classif. (of this repor t ) 20. Security Classif. (of this page) 21. NO. of PagesNone None 13

12. Sponsoring Agency Name and AddressNational Aerona utics and Space AdministrationWashington, D. C. 2054615. Supplementary Notes

22. Price$3.00

3. Recipient's Catalog No _.5. Report DateMav 1974

6. Performing Organization Code

8. Performing Organization Rep ort No.JSC S-396

10. Work Unit No.9 56-22 -00- 00- 72

11. Contract o r Grant No.

13. Ty pe of Report and Period CoveredTechnical Note

14 . Sponsoring Agency Code

1 16. AbstractThe development of flight-control fac ili tie s for the Apollo Progr am is reviewed fr om t he viewpointof t he us er organization. These facilities a r e treated in three categories: data system s, ground-based display and control syst ems , and configuration management.Pr ogr am fac to rs on the selection, sizing, and configuration management of the se sys tem s a r ediscussed.of s ystem sensitivity t o the program factors.

The effects of c er ta in ApolloRecommendations a r e made regarding improvement of the s ys tem s and the reduction


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control center (MCC) were used extensively during Project Mercury and the Gemini Pro-gram.mission-control team located in the MCC; the remo te-si te team relayed decisions andimplemented approved actio ns. However, if time did not permit, the remote-si te teamcould take action and make decisions based on mission rules that were established pre-miss ion. Early in the Apollo Pr og ra m, the approach of centr alized control includedboth manned and unmanned re mo te sites. This dual approach nec essit ated two uniquese ts of remote-site computer progr ams. The progr ams for the unmanned sit es providedcra ft fr om the MCC, where reliabl e communications could be provided. The pr og ra msfor the manned si te s provided disp lays of tele metry and track ing data and local commandcontrol to flight-control person nel located at the site. This approach imposed a heavyprogram-development, checkout, and maintenance workload. The re su lt s wer e elimi-nation of many desi rable requirement s, lat e delivery of the pro gra ms to the sit es, anddegraded reliability. When communication sat ell ite s became operational before theApollo 5 mission, relia ble worldwide communications wer e available; there fore, mannedremote sit es were eliminated for the remain der of th e Apollo Pr og ra m.

If time permitted, all decisions and actions wer e approved by a centralized

high-speed telemetry and tra cking dat a to the MCC and command control of the spa ce-

FLI GHT-CONTROL DATA NEEDSThe instantaneous bandwidth of t he combined vehicle te lem etr y downlinks ( i.e . ,

100 to 200 kbps) great ly exceeded the flight-control data need s; the ref ore , the conceptof "display a few paramet ers at a time with rapid acces s to all others" w a s adopted andapplied to the data flow from the rem ote si te s to the MCC and to the data display in theMCC. The data-flow sys tem provided a lib rar y of data-flow fo rm at s (each fo rm at con-taining a maximum of 2 . 2 4 kilobits of vehicle telemetry data) from the remote s it es tothe MCC (table I). The formatti ng technique used w a s a combination of vehicle selection,par ame ter selection, and sampl e-rat e reduction techniques.During the first few Earth-o rbita l mis sions , involving only a booster and either

the command and service module (CSM) o r the lunar module ( L M ) , only one high-speeddata format at a time w a s required fro m each remot e site . During the lunar missions,the need w a s increased to two simultaneous high-speed data for mat s from each remo tesite. This change w a s a re su lt of th e two new high-activity phase s: the lunar-landingand the lunar-launch phases, in which both the CSM and LM were active. High-speeddata-format-selection control w a s exercised from the MCC.

The concept of "display a few param eters at a time with rapid acce ss to all others"w a s also applied to the computer-driven television (TV) displays. The pa ra me te rs thatwere available from high-speed data form ats at the MCC wer e placed on computer-drivenTV display formats so that only a few display f or ma ts had t o be displayed at a given time.

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TABLE I. - DATA-FLOW FORMAT CONSTRAINTS

Format name

SLV/CSM backupSLV launchLM onlyCSM and LM PCMb (no OBCC)CSM and LM backupCSM maneuver and LM coastCSM onlyCSM PCM only (no OBC)

dSPS burnLM maneuver and CSM coastErasable memory dumpSLV orbi tCSM only (Program 22)OBC data

asaturn launch vehicle.bpulse code modulation.dCOnboard computer.

Serv ice propulsion sys tem.

Vehicle forma t bit rate , bpsSLVa10752 150

000000000

215000

CSM1075

00

95010501600224022402240

420(e)

02240

420

LM00

224011501150

640000

1820(e)

00

1820

eOptimum manner of formatting determined by implementing organization.

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SELECTION OF T E R M IN A L D I S P L A Y D E V IC E SB a l a n c e of G e n e r a l-Pu p o s e a n d S p e c i a l-Pu p o s eD i s p l a y D e v i ce s

The concept of a general-purpose display device such as TV was adopted to allowlarg e variations in display-presentation techniques and to provide acc ess to lar geamounts of data in a small console area. The limitations of any genera l-purpose devicefor special applications were recognized. Theref ore, the genera l-purp ose devices wereaugmented by the use of special-purpose display devices to provide such chara cte ris tic sas high sample rate , high accura cy, attention getting, and time histor ies. This conceptof a balance between general-purpose and special-purpose display devices w a s veryuseful in both the Gemini and Apollo Pro gr am s. The choice of what balanc e to use issubjective and is sensit ive to the nature of the program being run and to the level of ex-perience with si mi la r functions. As an example of the effect of the experience level,CSM systems monitoring w a s very similar to previous manned spacecraft monitoring;the ref ore, the general-purpose TV displa ys we re used extensively. However, scientific-experiment operation for th e Apollo lunar sur fac e experiments package (ALSEP) w a s newto flight control, and unique special-purpose display devices (i.e., drum recorders,multipoint rec orde rs, and meters) were used for experiment-data presentation. A s ex-perience is gained with scientific-experiment operation, an additional category ofgeneral-purpose display devices may be added to the cur ren t display syst em.

G e n e r a l - P u r p o s e D i s p l a y ( T e l e v i s i o n )The TV display system is the prime general-purpose method of display within theMCC. Analysis of required display charact er is ti cs such as c1arit.y and density of datapresentation, data sour ces, distribution of di splays , and hardcopying of th e dat a resulted

in the choice of the high-resolution TV technique. This selec tion w a s based on the easeof distri bution and on the types of input information to th e display s ys tem. Of the fivecategories of inputs, four wer e scenic . The inputs a r e as follows:

1. Computer-driven displays (the only nonscenic type)2. Opaque televiewers (c ame ra s mounted over ta bles in rem ote locations withinthe MCC and used fo r such manually prep ared information as trend plots, drawings,and Flight Plan revisions)3 . External TV (Kennedy Space Center launch TV and spacecraft TV)4 . Reference slid e files5. Other ca me ras within the MCCThese sour ces a r e routed through a switching matrix to provid e outputs to individ-ual console T V monitors, ceiling-hung TV moni tors, and large projection group-displaymonitors. Of these various input so urce s, the computer-driven di splays and the opaque

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televiewe rs a r e the most useful. External TV provided a significant addition fo r thelaunch and spacecraft TV cam era presentations. The refe renc e slide file, designed toprovide rapid ac ce ss to document sto rage , was of little use because of the const rain tsplaced on text data (i.e . , information could not be taken fro m existing documentation be-cause sp ecial text formatting w a s necessary for TV presentation).The categorie s of computer-driven display forma ts a r e alphanumeric tabulations,

X -Y and time-history plots, met er rep resentati ons, and schematic and dynamic digital-dat a combinations. The alphanumeric tabulations, X - Y plots, and time-hist ory plotshave been used extensively and a r e considered the most adaptable type presenta tion forcomputer-driven TV. The met er r epresenta tions were eventually deleted from thesyst em because of the poor quality of the display formats. Presentation by a schematicthat included dynamic digital data w a s tried on sev era l occasions. This category provedto be satisfactory from a data-presentation standpoint; however, reconfiguration of thecategory was very costly when compared to the cost for alphanumeric tabulations.Ther efor e, thi s category should not be considered as a standard format category andshould be used only in special c ase s.

During the Earth-orbi tal flights of the Apollo Prog ra m, a complement of28 computer-driven TV channels w a s sufficient. However, expansion to 36 channels wasrequired for the Apollo lunar-landing missions.

Two control modes were provided for the TV display syst em. The capabil ities aredisc usse d in the following sections .Display request mode. - An individual console may request a display for mat; the

computer gen erates the data, for mat s the display, outputs the data to the next availablecomputer-driven TV channel, and automatically connects that channel to the TV monitorof the requesting console. The concept of a computer-driven channel assignment wasbased on a "first come, first served" basis as opposed to consigning channels to displaysor consoles. Initially, difficulties were experienced when all channels were being usedand additional critical displays were needed. To provide positive control, a new displayformat w a s added to identify which display format w a s on each channel and to identifywhich console had requested the display. Through the use of this display, the flight-control team could determine which display for mat s to rel eas e to the proper channels.channel and rec eive s whatever data a r e on that channel. This concept of sharin g TVchannels has been very workable and has resulted in the need for significantly fewerchannels.

Channel attach mode. - In the channel attach mode, a console requests a given TV

A hardcopy subsystem w a s included as par t of the TV display syste m. The re -quirements for this subsystem were the same as for TV display (i.e., hardcopy of bothdata and scenic-type displays). This subsystem has been unsatisfactory because of poorlegibili ty. Experience gained during the Apollo Pr og ra m has proved that only computer-driv en data displays need to be hardcopied and, therefore , that the scenic hardcopy re-quiremen t could be eliminated. This would make poss ible the use of many existing dir ec tcomputer printout/plotting devi ces instead of the cu rre nt TV photographic-hardcopysubsystem.

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Special-Purpose Di play DevicesEvent modules. - The event module is a special-pu rpose display device used exten-sively on consoles . Initially, events we re grouped 18 and 36 events pe r module. Theinitial concept wa s to provide only those events on event modules that w er e applicableto all mission phases; all other event displays wer e to be provided by the us e of thecomputer-driven TV syst em because these displays can be released when not in use.However, experience showed that f e w events met this c rite rion; therefore, the evolutionof the us e of event modules during the Gemini and Apollo Pr og ra ms r esul ted in the c ur -rent concept that the pr im e method of event display is the us e of event ligh ts. Thi sconcept change caused a significant in crea se in the si ze of the event-display hardwareand software, including the development of 72-event modules for high-density event di s-

play. Because the original syste m was designed for expansion, no significant problemwas encountered. Event-light modules are used extensively, both in the miss ion oper-ations contro l room (MOCR) fo r prim e-p ara met er monitoring and in the staff supportrooms for detail-parameter monitoring. The two sou rce s of event drive s ar e the real-tim e computer complex (the sa me computer that d riv es the co mputer-driven TV chan-nels), which is required for param eters that must be processed or limit sensed at ara te no grea ter than once per second; and a pulse-code-modulation (PCM) ground sta tio n,which is requ ired fo r high-sample-rate event disp lays . In the ear ly pha ses of the ApolloPro gra m, event displays directly fro m the ground station (i.e . , bypassing the computer)were also desired because of a lack of confidence in inline computer sy st em s.

__-nalog strip-chart recor ders. - The analog strip-chart rec ord ers wer e used pri-marily for detailed analyses of sy stem pa ra me te rs (especially those requiri ng high Sam-ple rates) ; therefore, the recor der s were in the staff support rooms. These rec ord ersal so bypassed the computer and wer e driven dire ctl y out of the PCM ground s tation.Two strip -char t re co rd er s used in the flight dynamics staff support room (SSR) wer e anexception because they were used to display guidance parameters that had to be processedby the real -time computer complex. Thes e two strip -ch art r ec or de rs were viewed byTV; the pickup ca me ra s viewed the strip-c hart re co rd er s directl y. This TV method ofdisplay was very useful and was extended to ALSEP scientific parameters (i .e . , X-, Y-,and Z-axes of the lunar se ism ometer ). More extensive us e of TV fo r the display of an-alog para meters as a function of ti me is anticipated. The two methods of T V presenta-tion of analog display investigated fo r the rem ain der of the Apollo Prog ram we re the us eof TV-viewing str ip-ch art re co rd er s fo r high-sa mple-rate presentatio n and the use ofcomputer-generated time-history plot s.

Analog met ers . - Experience in the use of analog meter s as an end-display devicehas been interesting, and seve ral conclusions can be made. Initial attempts were madeto depict meter-type displays on the computer-driv en TV displays. As mentioned in theTV discussion, thi s method w a s unsatisfac tory and, because proportionately la rg eamounts of computer capacity were req uir ed, the method was discontinued. The use ofhard ware me te rs increase d immediately after the elimination of m et er r epre sent atio nson computer-driven T V displays. These hardware mete rs were driven directly fro mthe PCM ground statio ns by digital-to-analog conv er te rs . A common rationale was usedregarding the hardware meter s, the event-light panels, and the strip-ch art rec ord ers .Initially, the user s had little confidence in computer-dri ven displa ys; ther efore , me te rsdr iven by th e PCM ground station provided a backup to the compu ter-driven dis plays.As confidence in the computer displays increas ed, the number of hard ware met er s wasreduced. The change in me te r number and location as the Apollo P rog ram progressedexemplified this increase in confidence. For the AS-201 mission in February 1966,

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which w a s a Saturn-IB (S-IB) launch-vehicle-only mission, 30 met ers were in the MOCR.For the Apollo 5 mission in January 1968, which involved an S-IB launch vehicle and anunmanned LM, the number of met er s had increased t o 49. For the Apollo 6 mission inApril 1968, which involved a C5 launch vehicle and an unmanned CSM, a maximum of68 met ers w a s reached. At thi s time, a strong trend developed to move the met er sfr om the MOCR to the staff support rooms. By the time of the Apollo 13 mission inApril 1970, only 4 3 met ers were left when al l vehicles were required.

In summa ry, the following conclusions can be made about mete rs. Early in theApollo Pr og ra m, heavy rel iance was placed on me te rs because of lack of confidence incomputers. As the number of vehicles increased during the e arly missions, the numberof m et er s increas ed proportionally. Midway through the program, a shift w a s noted;most of the me te rs were relegated to the staff support rooms for detail analysis. Thisshift represented an increase in reliance on the computer-driven TV displays. Finally,a reduction in the number of m et er s occurred a s the staff support rooms reli ed on thecomputer-driven TV displays. The last prim e use for me te rs in the Apollo system w a sfor the detailed monitoring of the Saturn launch vehicle, a short-lived, highly activesystem.Projection-plotting devices. - The pro j ection-plotting devices wer e implementedduring the Gemini Pro gra m. Standard, direc t-writ e X -Y plotboards were used asbackup dev ices because the proj ection-plotting devices were a developmental system,The backup direct-write plotboards were removed early in the Apollo Program after theproj ection-plotting devices became operational. The proj ection-plotting devices we reused prim aril y for tr ajecto ry displays (e. g. , velocity as a function of flight-path angleplots with limit lines). The devices we re also used as general-purpose displays to de-pict the mission progress (i .e . , the relative location of t he spacecra ft during tran slun arcoast).Event recorders. - Event reco rders provided accura te high-sample-rate time

hi sto ri es of events. Initial implementation for the Apollo P rog ram was a 200-event pencapability in a remotely located equipment room. By the time of the Apollo 11 mission,verif ication of event occurrence in a time-dependent manner became a necessary taskof the vehicle syst ems SSR; therefore , an additional 400-event pen capability w a s addedin the vehicle systems SSR. These re co rders were not collocated with the consoles be-cau se of floors pace constraints.co rd er s and conso les had been collocated; however, collocation was not consideredmandatory because most of the events were duplicated on the console event lights andthe computer-driven TV formats.

Recorder utility would have been improved if the re-

Unique display devi ces. - A unique cardioscope display module w a s used fo r pres-entation of ast ronaut hear t waveforms. The cardioscope w a s chosen instead of the TVbecause of t he high accuracy of waveform that was requir ed. The cardioscope paral leledthe sam e information on strip-ch art rec ord ers in the medical SSR. Heart and respira-tion rates we re presented on special-purpose digital-read-out modules as par t of a uniqueinput-computation syst em for the flight surgeon. A third category of unique display de-vices was the event-sequence-override module. The use of these modules was discon-tinued because many spacecraft syst ems had different event sequences depending on themode of sy st em opera tion. Computer-driven TV w a s used where event sequences wereof intere st. The need to overri de telemetry events diminished as confidence in thespacec raf t and ground telemetry syst ems improved through the use of cross-checking ofdifferent parameters .

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MANAGEMENT OF GR OUND -SYSTEMS CONFl GURA Tl ONA s used in thi s repor t, configuration requirements r ef er to the specification of thearrangement of the ground-systems data fo rm at s, displays, and controls. Because Of

the developmental nature of the Apollo Pr ogram and the short launch inte rvals , requir e-ments were levied against the ground sys tems to provide various degrees of configurationflexibility from mission to mission. Therefore, the configuration requiremen ts wereconstrained t o be within the configuration capability of t he original ground sys tem design.

C o n f i g u r a t i o n - R e q u i r e m e n t C a t e g o r i e sConfiguration requiremen ts were divided into six categories based primarily o nthe leadtime needed for the reconfiguration of each category.1. Callup of remo te si te facili ties and interfaces2 . Data-flow format configuration ( i.e. , the parame ters and sample ra te in each

format , within the cons traint s given in table I)3 . Special data process ing of a mathematical nature (e . g. , the determination ofthe fuel volume from p re ssu re and temperatu re telemetry measurements)4 . Command-system configuration (e. g. , the command-execute panel arrange-ment and the identification of which commands a r e to be stor ed in the remote-s it e com-pu ter s for mission execution)5. Display-system configuration (e . g. , the layout of t he computer-dr iven T Vdisplay formats and the arrangement of par ameters on event panel s, me te rs , andrecorders)6 . Intercommunication panel configuration (e. g. , ac ce ss to the various loops andloop arrangement on the panels)

D o c u m e n t a t io n M e t h o dThe method of documenting the configuration req ui remen ts evolved fr om a methodof wr iting the requir ements in text form, as w a s done in Project Mercury, to a hybridmethod of computer-generated/manual text preparation. The us e of computer -generateddocumentation w a s valuable where many configuration changes we re caused by a devel-opmental flight program such as the Apollo Program (i.e. , early missions had few ve-

hicles and simple mission profiles, whereas l at er mi ssions included mo re numerousand mo re highly developed vehicles and complex mission profiles). Three advantagesof the computer-generation method were as follows.1. The computer could sor t the req uir emen ts efficiently. (The requirements wereprepa red according to flight-control function, such as all configurations applicable tothe CSM guidance function, whereas the implementing organization pre fer red groupingrequirements by system, such as all data-flow configuration requirements.)

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2 . The changes from previous miss ion configurations were identified easily.3 . Maximum use w a s made of previous mission-configuration requirements with-

out having to retype and check the unaffected configura tions. Manual text prepara tionw a s st il l requir ed fo r the specification of new or modified special data-p rocessingrequirements.

Sin gle -Po int Coordina t ion, Review, and ApprovalConfiguration-requirement management was accomplished by one flight-controlorganization. The respons ibili ties of this organization we re to ensu re that scheduleswere met, policies were applied, requ irements were integrated, duplication was avoided,requ irements wer e within the capability of the syst ems, and late requir emen ts wereevaluated from a standpoint of justification and impact.

Schedu esThe schedule fo r submittal of configuration req uir eme nts began with the initialsubmittal 10 months before the mission.9 months and 1 month before the mission, depending on the requir emen t category .(Changes t,o the data-flow for mat s we re terminated at 9 months premission, changes tospecial data-processing requirements were terminated at 8 months premission , and all

configurations wer e terminated at 1 month premissio n. ) Generally, these requirementcutoff dates we re a res ult of t he leadtime necessar y to implement and check out that r e-quirement category ; however, the last date at 1 month premissi on w a s to ens ure thattraining integrity w a s not affected by changing the system configuration.

Final cutoff dates were spaced between

The mo st significant configuration-requirement problem experienced during theApollo Pr ogr am was the long leadtime associated with thre e requirement categories .The se cate gori es wer e the most important ones from a vehicle-systems-monitoringstandpoint (i.e . , data-flow format configuration at 9 months premission and special dataproc essin g and computer-driven TV displays at 8 months premission ). The most sig-nificant fa cto r causing the long leadtimes was the design approach applied in the ground-sys tem s softwa re prog rams. Although the design approach provided for mission-to-miss ion reconfiguration, extensive prog ram checkout als o w a s necessary to ensurerelia bilit y. Th re e additional Apollo Progr am fac to rs combined with the long leadtimeto ca us e many requireme nts to be eliminated o r delayed until la ter in the progr am.Thes e thre e facto rs were the sho rt launch interval between missions, the lar ge volumeof req uir ement s, and the lat e changes to the flight vehicles or mission profiles after theground-system-requirement cutoff da tes had passed. As experienced during Proje ctMer cur y and the Gemini Pr og ra m, a larg e volume of configuration changes occ urr ed .This occurrence is characteristic of a developmental program wherein each successiveflight is mo re complex than the preceding.one, and the pro gram includes different m is-sion profi les and vehicles.until lat er i n the prog ram had les s than mandatory justification. Late mandatory re -quirements consumed a la rg e portion of th e available manpower and computer-hour re -so ur ce s because of extensive coordination and rete sting . Consequently, even mo renonmandatory requirement s often were eliminated or delayed, and flight-control pro-ced ure s in turn w ere changed late in the premission preparati on and training cycle.

Generally, the requirem ents that were eliminated or delayed

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C ON C L U D IN G REMARKSThe development of both manned and unmanned rem ote -si te computer p ro gr am s

caused an excess ive program-development workload. Initially, th is excess ive workloadresu lted in defici ent program content and reliab ility. When the communication sate lli te sprovided reliabl e worldwide coverage, the manned re mot e sites were eliminated; theres ult was highly reliable and satisf actory remot e-s ite pr og ram s. The concept of "dis-play only a few para met ers with rapid access to all others " proved t o be both feasibleand des irable . The amount of dat a that had to be monitored simul taneou sly and, there-for e, the sizing of the data processing, control, and display syst ems were proportionalto the number of vehicles that were active simultaneously. The number of har dwar e di s-play devices required to back up the computer-driven displa ys w a s inversely proportionalto the level of experience the us er organization had in using computer sys tem s. A str on gtrend toward computer-driven display s occ urre d as experi ence and confidence we regained.mission. This trend resulted in a significant improvement in the ability to monitor the

The concept of a balance between g eneral -purpo se and special- purpos e display de-vices w a s valid. As the siz e of the total display syst em was incre ased , the balance wasmaintained with a slight shift in favor of the gen era l-pu rpo se dev ices. When newmission-control functions were introduced (e. g. , scientific-experiment operations), theshift was strongly toward specia l-purp ose display devic es; however, as experience wasgained, the shift rev erse d in favor of the genera l-purp ose device s. The choice of tele-vision as the genera l-purpose display sys tem provided excellent flexibility of r ea l-t imeinformation-presentation techniques, data sour ces , and display distribution. An addi-tional type of genera l-purp ose display device oriented toward n ear- rea l-ti me and history -information display (i.e . , microfi lm) was considered. An evaluation of televisiondisplay sour ce s indicated that the most useful so urc es were the computer-driven displa ysand the opaque televiewer, whereas the ref ere nc e sli de file was unsatisfactory becauseof unique formatting constraints that were incompatible with standard documentation.An evaluation of television display format techniques indicated that alphanumerictabulations and plots wer e most useful. A sy st em s sch emat ics presen tation with dynamicdigital data w a s a good presen tation technique, but it s reconf igurat ion was costly .Because the me te r pictorial technique was unsatisf actory , it was discontinued. The twomethods of computer-driven television display ac ce ss (display request and channelattach) operated w e l l and reduced the siz e and cos t of the display system . The req uire -ment to hardcopy scenic television displays re sul ted in an unsatisfac tory hardcopysystem.and fac ili tate s the use of exis ting high-quality di re ct computer printout/plotting dev ices .Experience ha s shown that the elimination of t hi s requiremen t is acceptable

Th e application of computer -gen era ted document at on to configuration req uire men tswas beneficial in the Apollo P rog ra m and is expected to be beneficial fo r any complexdevelopmental flight pro gra m. The coordination, review , and approval of configurationrequirements by a single-point operations organization was approp riate to a developmen-tal flight program such as the Apollo Pro gr am.gen erat ed documentation and the advan tages of configuration-req uiremen t managementb y a single-point operations organization would be reduced grea tly for an "all-up" pro -gram such as Skylab.

However, the benef its of computer-

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A la rg e volume of configuration-requirement changes should be anticipated in anydevelopmental flight program . The long leadtimes fo r configuration requiremen ts werea significant problem in the Apollo Pro gra m. The leadtime is dependent on the initialdesign approach. Increase d emphasis should be placed on this fa ctor ( i.e . , rapid re-configuration, especially in the software systems) during the system s-design phase offutu re flight prog rams . Two concepts trie d in the Apollo Pr ogr am a r e applicable: themodular or tab le fill-in approach, which reduces o r eliminates th e need for extensiveprogram checkout after each reconfiguration; and the "universal" design approach, whichdoes not r equ ire reconfiguration (e. g. , the manual-select keyboard fo r televisiondisplay ac ces s and the digital-select matr ix fo r the univers al command system).

Lyndon B. Johnson Space CenterNational Aeronaut ics and Space AdministrationHouston, Texas, January 30, 1974956-22-00-00-72

NASA-Langley, 1974 S- 39 6 11


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apollo experience report flight-control data needs, terminal display devices and ground system...

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