A new carrier system has been developed for economical and quick response flight of small attached payloads on the space shuttle. Hitchhiker-G can accommodate up to 750 lb. of customer payloads in canisters or mounted to an exposed plate. The carrier connects to the orbiter's electrical systems and provides up to six customers with standard electrical services including power, real time telemetry, and commands. A transparent data and command system concept is employed to allow the customer to easily use his own ground support equipment and personnel to control his payload during integration and flight operations. The first Hitchhiker-G was successfully flown in January 1986 on STS 61C

Goldsmith, T. C.

English

NASA Technical Reports Server

N87- 20320
HITCHHIKER-G, A NEW CARRIER SYSTEM
FOR ATTACHED SHUTTLE PAYLOADS
T. C. Goldsmith
Hitchhiker-G Project Manager
Attached Shuttle Payloads
Goddard Space Flight Center
Greenbelt Md. 20771
301-286-8799
July, 1986
ABSTRACT:
A new carrier system has been developed for economical and quick response
flight of small attached payloads on the space shuttle. Hitchhiker-G can accom-
modate up to 750 lb. of customer payloads in canisters or mounted to an exposed
plate. The carrier connects to the orbiter's electrical systems and provides up to
six customers with standard electrical services including power, real time tele-
metry, and commands. A "transparent" data and command system concept is
employed to allow the customer to easily use his own ground support equipment
and personnel to control his payload during integration and flight operations. The
first Hitchhiker-G was successfully flown in January 1986 on STS 61C.
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HITCHHIKER PROGRAM
The Hitchhiker Program was initiated in early 1984 by the NASA Office of
Space Flight with the objectives of providing a quick reaction and low cost capa-
bility for flying small payloads that required somewhat more services than Get
Away Special (GAS) experiments but did not require the extensive, custom, ser-
vices of a Spacelab. The Hitchhikers are to be flyable as little as six months
after being manifested and will be flown four times a year on an opportunity
basis. Two versions of Hitchhiker were selected: Hitchhiker-G, developed by
Goddard, can carry up to six customer payloads weighing a total of up to 750
lbs.; Hitchhiker-M, to be developed by Marshall, will carry up to three payloads
for a total customer weight of up to 1170 lbs. The electrical and mechanical
interfaces of the two Hitchhiker carriers are different but the program manage-
ment and manifesting will be done in a similar manner.
Hitchhikers and their payloads are provided with power, command, and data ser-
vices from the orbiter using a new special harness in each orbiter which allows a
Hitchhiker to be flown without interfering with up to four primary payloads on
the same flight. Hitchhikers are carried in "bays" 2 and 3 near the forward end
of the payload bay. Hitchhiker-G is side mounted on the starboard side to avoid
interference from the RMS which is normally carried on the port side. In order
to meet the requirement for quick reaction Hitchhiker-G is designed with stan-
dard pre-defined electrical interfaces and also has special transparent data system
features to reduce the time required to perform electrical integration and check-
out of the customer hardware to the carrier. Mechanical interfaces are also
simple and consist of a flat vertical plate with a 70 ram. grid hole pattern or a
canister similar to GAS with or without a motorized door.
Hitchhikers are considered secondary payloads and may not interfere with pri-
mary payload requirements on the same mission. Unique crew activity and atti-
tude (pointing) requirements of a limited nature (eg. several hours) can usually
be accommodated but may extend the lead time requirement.
SHUTTLE PAYLOAD OF OPPORTUNITY CARRIER (SPOC)
The Hitchhiker-G was implemented using the Shuttle Payload of Opportunity Car-
rier (SPOC). In addition to Hitchhiker-G, SPOC is being used to support non-
Hitchhiker programs which are manifested as primary payloads and are therefore
not limited with regard to payload weight, crew activity, pointing requirements,
etc. within the normal STS capability. Currently the largest of these is the
Shuttle High Energy Astrophysics Laboratory -2 (SHEAL-2) which weighs over
12000 lbs. and is over 20 feet long.
The SPOC system is designed to be modular and expandable in accordance with
payload requirements to allow maximum efficiency in utilizing orbiter resources
and thereby increase the potential for early manifesting on the Shuttle. Various
SPOC configurations starting at 500 lbs. total weight are shown in fig. 1.
(Hitchhiker-G is confined to configurations occupying only two bays.)
The SPOC system consists of the following elements:
The avionics unit provides standard electrical interfaces for up to six customer
payloads. It contains a microprocessor control unit, relay switching equipment,
128
medium-rate multiplexer, and other hardware necessary to interface with the cus-
tomer hardware and orbiter. A small hand controller in the cabin allows the
crew to activate and de-activate the payload and provides an independent com-
mand path to control inhibits to any hazardous functions.
The SPOC plate provides a 50 by 60 inch mounting surface for the avionics and
customer hardware. The plate accepts 3/8 inch bolts on 70 ram. centers and is
equipped with heaters, thermostats and thermistors for maintaining and measuring
thermal control of the plate and mounted hardware as well as thermal blankets
and surfaces for the back and unused portions of the front of the plate. Plate
mounted customer hardware may need additional customer provided blankets,
heaters, or other thermal control provisions.
The SPOC motorized door canister has mechanical interfaces nearly identical to a
GAS canister and can accommodate a customer payload of up to 170 lbs., 19.75
inches in diameter and 28 inches deep. A sealed canister (no door) can also be
chosen and can accommodate 200 lbs. of payload in an atmosphere of nitrogen or
air. The canisters are not insulated and can radiate somewhat more heat than
GAS canisters. The customer's payload must contain heaters and thermostats to
maintain the desired temperature.
The standard electrical interface or "port" consists of a signal cable and a
separate power cable which provide the following:
o Two 28 V (+/- 4 V) 10 Amp. power lines which can be turned
on (together) by ground command. Customer power and energy
are monitored by the carrier system. The maximum simultaneous
total customer power for a Hitchhiker is 1300 W and the nominal
maximum total customer energy is 6 KWH/ day with additional
energy negotiable.
o F9ur 28V bi-level or pulse commands (10 ma max) which can be
used with relay drivers and relays to control additional power
switching within a payload. (For canister payloads one command
is reserved for control of the door.)
o An asynchronous 1200 baud uplink command channel.
o An asynchronous 1200 baud low-rate downlink data channel.
This data is available over Ku-band service or S-band service and
can also be recorded on the orbiter's tape recorder.
o A medium-rate downlink channel 1-1400 KB/s for use with the
real-time-only Ku-band TDRS service. The total simultaneous cus-
tomer data rate for the Hitchhiker-G cannot exceed 1400 KB/s.
o IRIG-B serial time code and a one ,pulse per minute square wave
signal which can be complemented oy a time command via the
aSove asynchronous uplink channel.
o Three channels for temperature sensors to allow measurement of
payload temperatures even when the payload Rower Is off (for
canister payloads these channels are reserved for door position,
canister pressure, and temperature).
o An analog channel, 0-5¥, 8 bit quantizing, 10 hertz sample rate.
An index pulse is also supplied which can be used to advance a
user supplied analog multiplexer to allow measuring a large num-
ber of parameters.
129
In order to provide low cost, quick reaction, and increased autonomy for the
customer, SPOC has been implemented with a transparent data system concept
(fig. 3). The Customer provided Ground Support Equipment (CGSE), associated
software, and personnel can be used to generate commands to the customer's pay-
load and display data from the payload during payload to carrier integration and
verification testing and also during flight operations. The asynchronous data and
command interfaces, and medium-rate data interface are transparent in that the
interface between the customer's flight hardware and the carrier is identical in
electrical characteristics and protocols to the corresponding interface between the
SPOC GSE and the CGSE thus the GSE the customer used during development of
his instrument may be used without modification during carrier integration and
flight. The remaining interfaces (bi-level commands, analog channel, etc.) can
also be connected but require conversion to asynchronous format at the CGSE. If
desired the CGSE can also be provided with orbiter attitude and position data.
These interfaces operate in real-time with transmission delays of 5-15 seconds
during flight. Simpler experiments with minimal command and data display
requirements can be accommodated without customer delivered GSE. All of the
data is available on magnetic tape within one month after the flight.
HITCHHIKER-G MANIFESTING SCENARIO
Prospective Hitchhiker-G customers first discuss their requirements with the
Goddard Project Office to determine feasibility and compatibility with the
Hitchhiker-G capabilities. They then submit a Customer Payload Requirements
(CPR) document to GSFC and a Request for Flight (NASA form 100) through
NASA Headquarters. When accepted by Headquarters, payloads are placed in a
queue system (currently being developed) and then selected for flight on a spe-
cific Hitchhiker-G mission. Sources of payloads are expected to include NASA
sponsored, DoD sponsored, participants in NASA Joint Endeavor Agreements or
Foreign cooperative agreements, and (when pricing policy is completed) other
customers. Prices for commercial use of Hitchhiker-G haven't been finalized but
are expected to be on the order of several hundred thousand dollars for a one
port payload.
Approximately 8 months before flight the customer delivers complete documenta-
tion on his payload to GSFC. The safety data package requirements are similar
to GAS in the case of canister payloads but are somewhat more complex if the
customer's equipment will be plate mounted. About 4 months before flight the
customer's hardware is delivered to GSFC and with the help of the customer and
his CGSE the payload is integrated to the carrier, and system functional tests
and EMI tests are performed. Prior to delivery the customer is responsible for
performing any necessary tests required for safety certification (such as static
load tests) as well as any tests required by the customer to confirm proper oper-
ation (such as vacuum or vibration tests). Following tests at GSFC the integrated
payload is shipped to Kennedy Space Center and integrated into the orbiter
where only interface verification tests are performed. Launch occurs typically
about 8 weeks after orbiter integration. During flight the Hitchhiker-G is oper-
ated from a control center at GSFC with participation of the customers and their
CGSE. Displays of orbit position, attitude, ancillary data, and any downlink TV
are provided along with access to crew voice transmissions. Following landing
the Hitchhiker-G is removed and de-integrated and the customer hardware is
returned to the customer at GSFC.
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HITCHHIKER-G MISSIONS ) • 't.
The Hitchhiker-Gl payload (fig. 4) flew on STS 61C in January 1986. The cus-
tomer payloads were: The USAF Particle Analysis Cameras for Shuttle (PACS)
which was designed to make photographs of particle contamination in the vicinity
of the orbiter; The NASA/GSFC Capillary Pump Loop (CPL) experiment which
determined the zero-gravity performance of a proposed Space Station thermal
system; and the NASA/Perkin Elmer Shuttle Environmental Effects on Coated
Mirrors (SEECM) experiment which studied the effects of residual atmosphere on
telescope mirror contamination. The PACS consisted of a stereo camera and flash
assembly mounted on the upper portion of the plate. The CPL instrument was
carried in a sealed canister and was connected to multiple power ports to allow
over 1000 W of power to be used. The mission was successful and the experi-
menters are currently studying their data. The carrier operated nominally with
over 800 commands being sent and over 120 hours of data obtained. A number
of minor ground system problems are being corrected for the subsequent flights.
Hitchhiker-G2 will carry a USAF/NRL Ultraviolet Limb Imaging Experiment
(UVLIM) which will scan the horizon to obtain data on the constituents of the
atmosphere; the NASA/GSFC Pumped Two-Phase (PTP) experiment which will test
Space Station thermal control equipment; and a NASA/JSC Plasma Motor Gener-
ator experiment which contains a probe to be ejected from a canister during the
flight.
FUTURE ENHANCEMENTS UNDER STUDY
The following are enhancements which may be added to the SPOC system in the
future depending on demand and feasibility:
o An ejection mechanism to allow deployment of small probes or
.spacecratt from the canister. This would be similar to the exist-
lng GAS system except that power and elactrical services could be
obtained prior to launch via an umbilical connector. Spin-up
capability is also being studied. Payloads up to 150 lbs. could be
accommodated.
o A larger canister with ejection mechanism for larger attached or
ejected payloads up to approximately 350 lbs. and 30 inches in
alameter.
o A method for late installation of payloads into motorized door
canisters on the launch pad to reduce the time-to-launch from 8
weeks to 2-3 days.
o A probe bus for ejectable experiments is being considered. This
bus would be ejected from a canister, contain batteries, .data sys-
tem, transmitter, and receiver and would carry a customer's instru-
ments for a brief mission in the vicinity of the orbiter while
communicating to an antenna and SPOC port on the attached car-
rier.
131
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132
SPOC i "!"-..._ ORBITER
CORE PLATE GAS BEA_ _ ...,._/
_--------_ UPPER CLAMP ,_ _ _'t,
AV,O,,,cs ox i.i ilii",iii-i
_ I t -'" _:lJ _FIELo
_ SECTION
Fig. 2 SPOC PLATE
CUSTOMER I_ CUSTOMER _ CUSTOMER
PAYLOAD GROUND SUPPORT OPERATOR
(CP) EQUIPMENT
(CGSE)
AT CUSTOMER'S FACILITY
_H_ sPo_ I I C_,E. I I CO=_OM_RI ICUSTOMER DATA _ GROUND SUPPORT L_ GROUND SUPPORTPAYLOAD SYSTE (CCGSE) (CGSE)
AT CUSTOMER CARRIER INTEGRATION
CUSTOMER
OPERATOR
CUSTOMER
PAYLOAD
ORBITER GROUND SUPPORT GROUND SUPPORT
EQUIPMENT EQUIPMENT
(CCGSE) (CGSE)
AT FLIGHT OPERATIONS
CUSTOMER
OPERATOR I
Fig. 3_ SPOC TRANSPARENT DATA SYSTEM COMMUNICATIONS
133
Fig. 4 HITCHHIKER-G1 PAYLOAD AFTER INSTALLATION INTO ORBITER
i iH
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