Simulation of Gemini-Agena Docking

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SIMULATION OF GEMINI-AGENA DOCKINGBy Byron M. Jaquet and Donald R . R i l e y

NASA Langley Rese arch C en te rLangley Station, Hampton, V a .

Presented a t Meeting No. 14 of Committee A-18,Aerospace Vehicle Flight Control Systemsof t h e SAE Aerospace Equipment Division

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N ew York, N.Y.J u l y 8-10, 1964


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SIMULATION OF GEMINI-AGENA DOCKINGBy Byron M. Jaquet* and Donald R. Riley*

NASA Langley Research CenterLangley Station, Hampton, Va .

INTRODUCTION

Ful l - sca le s imula t ions of the docking phase of Project Gemini have beenunde r i nves t i ga t i on a t the Langley Research Center for th e p a s t y e a r ( r e f s . 1and 2 ) .t ime, t he present paper w i l l only review information concerning Gemini-Agenadocking.

Since only a small por t i on o f t he d a t a can be presented in a shor t

The data presented herein are in troduced i n two separa te pa r t s .p a r t i s concerned with resul ts f rom a general s tudy i n which a p a i r o f f i n g e r -t i p c o n tr o ll e rs were used . These con t ro l le r s , one f o r a t t i tu de and one f o rtr an sl at io n, were not Gemini proto types. The primary purpose of t h i s study wast o obtain informat ion concerning fuel and t i m e requi red for docking wi th theprimary ra te command and the backup direct attitude control modes.

The f i r s t

The second pa r t of t h i s presenta t io n i s concerned wi th the eva lua t ion , forth e docking phase, of t h e two ba sic a t t i t u d e co nt ro l modes and protot ypes ofactual Gemini hand control lers .

The d ata p resented her ein were obtained wit h the Langley vi su al dockings imula tor .v i s io n t o provide f i l l - s ca le images of th e t a rg e t vehic le . The simula tor w i l lbe d i scus sed shor t l y .

This i s a f ixed-base type device which employs close d-c ircu i t t e l e -

DOCKING PHASE OF PROJECT GEMTNI:

Since the mission profile and the purpose of Project Gemini have been w e l ldocumented, they w i l l not be reviewed again. Following rendezvous, th e as tr o-nau t s w i l l begin th e docking maneuvers i n order t o achieve contac t between th etwo vehicles .be made wit hin c er ta in ve loc i ty and displacement to ler an ce s . During th e dockingpha se, maneuvering and alinem ent cues can be o bta ine d from out-of-the-windowobse rva t i ons o f t he t a rge t veh i c l e . It i s i n t h i s range tha t s imula t ion s tudiesof docking have been conducted a t Langley.c l es near ing complet ion of t he docking phase j u s t p r i or t o con tac t .

Des ign cons idera t ions of the two vehic les requi re tha t contac t

Figure 1 i l l u s t r a t e s t h e two v eh i-

~~~~*Aerospace Engineers.L-4163


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DESCRIPTION OF VEHICLES AND SIMULATORY

GeminiA br i e f de sc ri pt io n of t h e Gemini and Agena ve hi cl es i s pe r t i nen t be fo reproceeding t o th e s imulat ion results .

reent ry vehic le and a maneuvering uni t ( f ig . 1).8 a t t i t u de con t ro l engines and 8 t r ans l a t i on eng ines , a l l of which use hyper-g o l i c f u e l s. All engines are loca ted behind the spacecraf t c enter of gravi ty .Because of t h i s rearward engine loca t ion , coupl ing occurs between ve r t i ca l andl a t e r a l t r ans l a t i on -con t ro l i npu t s and t he p i t c h and y aw spacecraft motions.The pi t ch and yaw co ntro l inp ut s s i mi lar ly produce ve r t ic a l and l a t e r a lt r a n s l a t i o n s .

The Gemini spacecraft consists of theThe maneuvering unit contains

Two bas i c a t t i t ud e con t ro l modes a r e ava i l ab l e i n t he spacec ra f t f o rdocking.body ax is i s propor t iona l t o co nt ro l le r def lec t i on . The presence of ra te feed-back i n t he system e f f ec t i ve ly e l im ina t e s t he coup ling of t h e t r an s l a t i on -co nt ro l input s in to t he angular motions. The ba si c backup mode i s a d i r e c t o n-off acceleration command system.manually, t he co r rec t ion s necessary t o account fo r the coupl ing e f fe c t s . Withe i th er a t t i t ud e mode spacecraf t t r an s la t io ns a r e provided by an on-of f acce le r -a t i o n command system. Two th ree-axis hand cont ro l le r s are u se d t o a c t u a t e t h et ra ns la t io n and a t t i tu de engines. These w i l l be discussed subsequently.

The primary mode i s r a t e command with which angular ra te about each

With t h i s mode t h e a str on au t must provide,

AgenaThe Agena ta rge t vehic le ( f ig . 1) has a ?-foot-diameter, shock-mounted,docking ring on the front which serves t o channel the Gemini nose t o t he

coupling mechanism.on the Gemini nose provide r o l l posi t ion ing .The V-shaped s lo t i n th e docking r i ng and th e indexing bar

Visual Docking SimulatorThe visual docking simulator i s of th e f ixed-base type and s imulat es lon-g i t u d ina l d i s t ances up t o 300 f e e t and ve r t i ca l and l a t e r a l d i s t a n c e s up t o100 f e e t .An a r t i s t ' s ske tch of the v i sua l docking s imula tor i s shown i n f ig ur e 2.

Inc luded inThe sim ula tor co ns is ts of analog-computer equipment combined with a WAF F-151gunnery t r a i ne r which has been adapted f o r t h e s tudy of docking.t h e gunnery t r a in e r was a clo sed -cir cui t te le vi s i on system. Complete s ix-degree-of-freedom motion i s obtained from three angular degrees of freedom of a small-sc ale model of t h e Agena, t r an sl at io n of th e model i n f ro nt of t h e TV pickupcamera, and the azimuth and elevation motion of a two-axis mirror located abovet h e p i l o t ' s h e a d . A 20-foot-diameter sph er ic a l pro jec t ion screen enc loses af u l l - s i z e wooden mockup of t h e Gemini sp ac e cr af t. Computer equipment as so ci at edwi th th e gunnery t ra in er de te rmines the p os i t i on of th e model on th e range bed,

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t h e proper asp ect of t h e model, and th e proper azimuth and ele va tio n ang les oft h e mi rro r. The analog computer solv es th e six-degree-of-freedom equatio ns ofre la t ive mot ion .

RESULTS AND DISCUSSION

General Study of DockingThis s imulator has been used t o s tudy the g eneral a spe cts of docking usingth e f i n ge r t i p con t ro l l e r s shown i n f i gu re 3 . The t r ans l a t i on con t ro l l e r i s asimple on-off device with which t h e p i l o t maneuvers fo re and a f t , up and down,and l e f t and right with corresponding motions of the handle .t r o l l e r pr ov id es r o l l ( t w i s t ) , yaw ( ri g ht and l e f t ) , and p it c h (up and down)

motions by corresponding deflections.on a cent r i fuge wi th a pi lo t wear ing a pres su re su i t . The instruments shown onthe pane l are used pr imar i l y fo r check-out and p i l o t fam i l ia r iza t ion .

The at t i tude con-This cont ro l le r has had extens ive t es t s

A summary of some r e s u l t s of docking from about 300 f e e t up t o c on ta ctus ing t h e f i nge r - type con t ro l l e r s desc r ibed p rev ious ly w i l l now be presented.The data were obta ined wi th Langley research p i l o t s and engineers as t he simu-l a to r p i lo t s . Maneuvering cues were obtained only from the out-of-the-windowdi sp l ay .d i r e c t a t t i t u de con t ro l modes.The p i l o t s made th e docking runs using e i t h er th e ra te command o r t he

Figure 4 pre sen ts boundaries of fu e l and f l i g h t t i m e f o r t h e f o ur p a r t i c i -pants .60 percent and 85 percen t of t he t o t a l number of docking runs.from bot h t he 60-percent and 83-percent da ta boundaries t h a t more t i m e i sreq uire d t o complete docking when t h e d ir e c t mode i s used than when the primaryrate command mode i s used . This probably re su l t s from t h e more d i f f i c u l tp i l o t i n g t a s k a s s o c i a te d w i th t h e direct mode.i n d i ca t e t h a t a p i l o t a t peak proficiency could probably dock using l e s s f u e lwith t h e d i r e c t mode altho ugh he would tak e long er.p le te docking has not been spec i f ied the d i f fe rence in t i m e between the twomodes i s probably of l i t t l e consequence.

These boundar ie s r ep re sen t t h e f u e l and f l i gh t t i m e f o r t h e lo we stI t i s apparent

The 60-percent d at a boun dariesSince a given time t o com-

Design considerations of the two vehicles require that docking be accom-p l i s he d w i t h in c e r t a i n t o l e r a n c e s of veloci ty, posi t ion, and angular a l inement .Simula t ion s tudies a t Langley have indicated that a wel l - t ra ined p i lo t can sue-ces s fu l l y dock wi th in t h e spec i f i ed t o l e r ances us ing t h e ra te command mode. Toachieve the same degree of pro f icie ncy with th e d i r ec t mode req uir es moret r a i n i n g .

Pi lot Opinion Rat ingsThe a t t i t u d e c on tro l modes and prototypes of a ct ua l Gemini hand co nt ro l le rs

( f i g . 5 ) were evaluated during simulated docking runs.designed so t h a t an a s t r on a u t i n a pressure s u i t could operate each with handThese con t ro l l e r s were

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motions.t i o n s . This r a t i n g s c a l e w a s developed by Cooper a t the Ames Research Center Yf o r p i l o t s t o r a t e a i rp l a n e ha nd li ng q u a l i t i e s . I t has been employed for t h eevaluat ion of the Gemini at t i tude modes and hand control lers . Figure 7 p r e s e n t sth e ra t in gs f o r the two ba s ic a t t i t ud e modes avai lab le fo r docking. The pr imaryr a t e command mode w a s r a t ed , on the ave rage , w e l l w i th in the sa t i s f ac to ry r eg ionwhereas the backup direct mode w a s r a t e d j u s t b a r e l y s a t i s f a c t o r y .

Figure 6 p r e s e n t s t h e p i l o t o pi ni on r a t i n g s c a l e us ed i n t h e e v a lu a-

Figure 8 p r e s e n t s t h e p i l o t o p in i on r a t i n g s f o r t h e hand c o n t r o l l e r s . TheThe t r an s l a -resul ts are from two programs involving two groups of astronauts .t i o n cont ro l le r had not been previous ly used i n s imula t ion s tu die s . The ra t i ng sfo r t h i s con t ro l l e r were predom inately i n the unsa t i s f ac to ry r eg ion . The objec -t ionable features were uneven forces about each axis , loosenes s i n t he mecha-nism, and some bin din g when de fl ec te d. These f a c t o r s made i t d i f f i c u l t t o a pp lydes i r ed inpu t s . A s a r e s u l t of t hese s tud ies the con t ro l l e r has been r edes ignedand has s ince been rebui l t .

The a t t i t ud e c on t ro l l e r , u sed i n p rev ious s im ula t ion s tud ies , w a s r a t e de n t i r e l y i n t h e s a t i s f a c t o r y r e gi on .

CONCLUDING RENARKS

I n summary, Pr oj ec t Mercury has demonstrated t h a t sim ula tor s provide ar e a l i s t i c env ironment t o eva lua te co n t r o l l e r s and co n t ro l sys tems o f spaceveh ic les . With t h i s i n mind, t he present r es ul t s of fu l l - s ca le Gemini-Agenadocking stu die s ind ica ted th a t succ essf ul docking can be accomplished consis-t e n t l y w it h e i t h e r t h e p ri ma ry r a t e command mode or backup direct mode. Theuse of navigat ional ins t ruments i s not mandatory since an out-of-the-window viewof t he Agena tar ge t veh ic le suppl ies a l l of t he necessary informat ion t o performt h e docking ta s k. Suc cess ful docking with th e di r e c t command mode i s more dif-f i c u l t t ha n wi th t h e ra te command mode and r e q u i r es a h igher degree o f p i lo tp ro f i c i ency .

REFERENCES

1. Langley Research Center St af f : A Compilation of Recent Research Rela ted t ot h e Apollo Mission. NASA TM X-890, 1963.2 . Hatch, Howard G . , Riley , D. R . , and Cobb, Jere B . : Full-Scale Gemini-Agena

Docking Using Fixed-Base and Moving-Base S im ul at or s.1964. AIAA paper No. 64-334,

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Simulation of Gemini-Agena Docking

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