,

NASA TECHNICAL fi MEMORANDUM

b

COMMUNICATIONS SYSTEM FOR ZERO-G SIMULATION IN WATER

by H. E. SMITH Manufacturing Engineering Laboratory

N.iZS.4 TM X-53547

December 6, 1966

# NASA

I

L George C. Marshdl Space Flzght Center, Hantsuille, Aldbamd

TECHNICAL MEMORANDUM X- 53547

COMMUNICATIONS SYSTEM FOR ZERO-G SIMULATION IN WATER

BY

H. E. Smith

George C. Marshall Space Flight Center Huntsville, Alabama

ABSTRACT

This report presents a description of a two-way communications system connecting nine personnel stations and a public address system. The system includes underwater speakers that can be heard by the safety divers.

Operating instructions for the system are also given.

P NASA -GEORGE C. MARSHALL SPACE FLIGHT CENTER

NASA -GEORGE C. MARSHALL SPACE FLIGHT CENTER

TECHNICAL MEMORANDUM X- 53547

COMMUNICATIONS SYSTEM FOR ZERO-G SIMULATION I N WATER

BY

H. E. Smith

MANU FAC TU RING ENGINEERING LA BORA TORY RESEARCH AND DEVELOPMENT OPEFWTIONS

TABLE O F CONTENTS

Page

I SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

INTRODUCTION I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DESCRIPTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

OPERATING INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,4

SystemOpera t ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 System Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

APPENDIX - SYSTEM WIRING DIAGRAMS. . . . . . . . . . . . . . . . . . . . . 7

LIST OF ILLUSTRATIONS

Figure Title Page

I. Life Support Control Console ........................ 3 2 , Main Control Panel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Amplifier Control Panel ........................... 5

A- I. Speaker Control-Communications System f o r Zero-G Simulation in Water MRbTsK 1070-2. . . . . . . . . . . . . . . . . . . 9

A-2. Power Supplies for Communications System- Zero-G Simulation in Water MR & TsK 1070-1. . . ....................... 1 0

A-3a. Communication System for Zero-G Simulation in Water MR & TsK 1070-0 . . . . . . . . . . . . . . . . . . . . . . . . . 11

A-3b. Communication System for Zero-G Simulation in Water MR & TsK 1070-0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

iii

TECHNICAL MEMORANDUM X- 53547

COMMUNICATIONS SYSTEM FOR ZERO-G S l M U l A T l O N IN WATER

SUMMARY

A system providing communication between personnel conducting underwater neutral buoyancy experiments is described. system connects seven observers, a diver, and a spare station. Al l com- munications are broadcast over a public address system which includes under- water speakers.

The communications

The feasibility of providing two-way communication between the safety divers and other personnel is currently under investigation.

I NTRODUCT I ON

The Manufacturing Engineering Laboratory of the George C. Marshall Space Flight Center has been conducting tests concerned with fabrication, as- sembly, maintenance and repair of large s t ructures and associated apparatus under conditions of weightlessness. Zero-G simulation techniques using a water tank and a test subject in an underwater pressure suit are employed in these tests.

The pr imary safety requirement is to establish and maintain two-way communications between the test subject and personnel in control of life support. Tes t personnel must be advised immediately of any malfunction in the pressure sui t o r equipment so, that corrective action can be taken.

To avoid delay, a temporary communications system was designed and placed in service. This was a small, portable, 1 2 volt system with communi- cations between only two people and the man inside the suit. This was con- sidered adequate for testing the suit and for a few minor experiments. A l l requirements for the neutral buoyancy communications system were established by taking into consideration the following two items:

1. The safety of the diver

2. What was needed to adequately perform any anticipated future experiments.

DESCR I PT I ON

The system was designed with nine two-way communication stations, and three one-way stations. There is a main audio level control for the system with an individual audio level control for each station. cation units consist of the following positions:

The two-way communi-

1.

2.

3.

4.

5.

6.

7 .

8.

9.

Experiment Conductor

Life Support Controller

Medical Doctor

Data Engineer

Deck Safety Man No. I

Deck Safety Man No. 2

Video and Tape Recorder

Pressure Suit

Spare

The pressure suit must have two-way communications at all times. Al l other stations w i l l be on receiving at all t imes, with the transmission of any o r all positions (except the pressure su i t ) controlled by the controller at the main panel (Fig. I ) . The controller may select any of three modes of operation for any station (Fig. 2 ) : talk, p re s s to talk, or off. In the lttalkll mode, the operator

a switch before talking over the system. In the ftoffll mode, the operator can only listen. However, if he wishes to talk, he may depress the "press to talk" switch. This will turn on a light on the main panel indicating which operator would like to speak (Fig. 2 ) . The controller may then switch the station into the system o r not, as he so chooses.

I may talk at will. In the "press to talk" mode, the operator must first depress

2

FIGURE 1. LIFE SUPPORT CONTROL CONSOLE 3

FIGURE 2. MAIN CONTROL PANEL

The one-way stations are a public address speaker system designed to dr ive 20 watts peak audio power, and an underwater speaker system capable of driving 100 watts audio power. 50-watt amplifiers. underwater speakers. However, it has been determined that, f o r the 25-foot diameter , 15-fOOt deep tank, two 25-watt speakers are adequate. Therefore , the system was designed to switch either amplifier to ei ther set of speakers . This gives a capability of putting 100 watts of audio power into the water if it is needed, and a l so , during normal operation, furnishes a stand-by amplifier and a set of speakers in the event e i ther stops functioning (Fig. 3 ) . The opera- tion of the underwater speaker system is necessary a t a l l t imes because the safety d ivers need to hear all communications and should not be res t r ic ted with connecting cables.

The underwater system consis ts of two Each amplifier may be used to drive two 16-ohm, 25-watt

The complete system was designed to operate f rom a 12 volt battery as a stand-by power source. In the event of a power fai lure , the system may be switched to battery operation by turning the power "ON-OFF-BATT" switch to ' ' BA T T .

System wiring diagrams are presented in the Appendix.

OPERATING INSTRUCTIONS

Operation of the neutral buoyancy tank communication system is simple and straightforward. Instructions for placing the system in operation and shutting it down are presented below,

4

System Operation

I.

2.

Place underwater speakers 18 inches below water surface.

Turn power "ON-OFF-BATT1' switch to "ON. I '

3. Turn underwater speaker and amplifier switch to desired combina- tion (located on amplifier panel) .

4.

5.

Turn "SUIT VOLUME CONTROL" full clockwise.

Increase "MAIN VOLUME CONTROL" for des i red audio in sui t headset.

FIGURE 3. AMPLIFIER CONTROL PANEL

5

6. Adjust WNDERWATER SPEAKER VOLUME CONTROL" for desired underwater audio level. clockwise position, increase main volume control for desired level and then adjust sui t volume control. )

(If audio level remains low with volume control in full

7. Select mode of operation for each station, i. e. , "TALK, ' I "OFF, I ' or "PRESS TO.TALK. If The station 5 mode-selector switch controls the station on the left side of the front panel. The station 6 mode-selector switch controls the modes of operation for the station on the right side of the main panel.

8. Adjust public address "SPEAKER VOLUME CONTROL. If

9. Adjust each station VOLUME CONTROL" for desired audio level.

System Shutdown

i. Switch power switch to "OFF. ''

2. Turn underwater speaker switches to "OFF" (on amplifier panel).

3. Remove underwater speakers from water .

NOTE:

a. In the event of power failure switch power switch to "BATT" position.

b. Main amplifier volume control should be as low as possible fo r adequate audio level.

c. Underwater speakers should be removed from water when not in use.

RECOMMENDAT IONS

From the experience obtained in the zero-G simulation tank, it is felt that two-way communications between the safety divers and the test subject is necessary for maximum safety. At this time the safety divers can only listen. A system is now being designed that will furnish two-way communica- tions between the safety divers, the test subject, and all other stations; and will be in operation by May i , 1967.

6

APPENDIX

SYSTEM W IR ING DIAGRAMS

7

w

9

l l 5 V 60Q

ATR - DC TO AC-CONVERTER -1 - r-

ON 0 I T I

T2 .8A r - 7

I

~ i! q I

1 ' . I L- CHASSIS

ISOLATION TRANSFORMER

P-6160

3 0 \ Q

T O ALLEN T-x) AMFUFIERS

MDA952-I

5n 5w 0 - 2 4 V

IOOOJIF-- 5 0 VDC--

0 - I O V

1

FIGURE A-2. POWER SUPPLIES FOR COMMUNICATIONS SYSTEM - ZERO-G SIMULATION IN WATER MR & TsK 1070-1

10

I .

i . I N 3 4 4

> n 6 2 0 n 1/2 w

SIGMA 4F - IO00

1

- - - 50 n CARBON

MIKE I 3 I

I

I

I I

F 2N404 I

L 6 1 1 4 M A

PRESS f S6 DTALK ----

I f * I 4

OFF

P I THRU P 7 AMPHENOL ItXIlf 3 p6

TO SPEAKER JACK OF BENDIX MODEL D-200A

PB THRU P I 3

AMPHENOL 1 ~ ~ I ~ ~

PI4 THRU P 2 0 P T 0 7 P - B - 4 S 3 PTO 6E-B-4P - P x

50 IY .- _ _ CARE1 MIKE

FIGURE A-3a. COMMUNICATION SYSTEM FOR ZERO-G SIMULATION IN WATER MRdtTsK 1070-0

I STATION S

s o n la CARBON MIKE

IN34A e L 4 '4MA L

& P 4 [ I{ , CABLE

PRESS TO TALK

I ' ;4

TALK c

A+ SET I

CARBON MIKE

e

. 5 d SET

NOTES:

I. SEE MR e T sk 1070-1 8 - 2 FOR WIRING DIAGRAM ON POWER SUPPLIES AND SPEAKER CONTROLS.

Ad&

“el IN34A

p3 c CABLE 4:

PRESS TO TALI

t

5 3

2 TALK

L-7 I STATION 3 ‘?3 CARBON

IN34A el + P 2 [ ‘i CABLEi

& 6OOA HEADSET

P / I I

IN34A 1: I

I*-- I STATION I ’

SI

3 TALK

=L

FIGURE A-3b. COMMUNICATION SYSTEM FOR ZERO-G SIMULATION IN WATER MRkTsK 1070-0

I3

. . TO UNDERWATER SUIT

kL TO ALLEN T-50 AMPLIFIER

* -24VDC

- - PTOTE-8-2S PTOBP -8-2P