HS-376 explained

The Boeing 376 (sometimes referred to as the BSS-376, and previously as the HS-376) is a communications satellite bus introduced in 1978 by Hughes Space and Communications Company. It was a spin-stabilized bus, a successor to Hughes HS-333.

Design

The satellite bus was designed and manufactured by Hughes. This spin-stabilized platform had two main sections. The spinning section was kept rotating at 50 rpm to maintain attitude, and a despun section was used by the payload to maintain radio coverage.

The spinning section included the apogee kick motor, most of the attitude control, the power subsystem and the command and telemetry subsystems. The despun section contained the communications payload, including the antennas and transponders.

The stock version had a launch mass of 1100kgto1450kgkg (2,400lbto3,200lbkg), a mass of 540kgto790kgkg (1,190lbto1,740lbkg) after reaching geostationary orbit and an 8 to 10-year design life. When stowed for launch, its dimensions were 2.8mto3.15mm (09.2feetto10.33feetm) in height and 2.16m (07.09feet) in diameter. With its solar panels fully extended its height was 6.6mto8mm (21.7feetto26feetm).

Its power system generated approximately 1,100 to 1,200 watts of power at beginning of life, thanks to two cylindrical solar panels. The bottom panel was retracted around the body and top panel for launch, and extended downwards for operation. It also had two NiCd batteries for solar eclipses.

Versions

There were four variations of this platform:

• HS-376: The original version of the platform was launched in 1977. It had a mass between 1.1tonne1.45tonne.
• HS-376L: The Longer life version of the platform was launched in 1991. It had reduced power of 700 Watts and reduced electronics weight, which allowed for increased station keeping propellant supply. This lengthened the design life to 13.5 years.
• HS-376HP: A Higher Power version of the platform was launched in 1995. It had a mass between 1.45tonne1.55tonne.
• HS-376W: The Wide version of the platform was launched in 1990. It was wider, more powerful and modernized electronics. It was a joint development with INPE. It had a diameter of 3.43m (11.25feet) and more power.

Satellites

The HS-376 was a very successful satellite platform with 58 satellites ordered, built and launched. It was also the first satellite to launch from the Space Shuttle.

Satellite	Other names	Operator	Model	Ordered	Launch	Launch vehicle	Launch result	Mass (kg) at...		Remarks
								Launch	BOL
			HS-376	1977	1980-11-15			1117	540
			HS-376	1977	1981-09-24			1117	540
			HS-376	1980	1982-02-26			1100	582
			HS-376	1982	1982-06-09			1100	582
			HS-376		1982-08-26			1140	634
			HS-376	1978	1982-11-11			1140	563
			HS-376	1981	1982-11-11			1117	540
	Nahuel I2		HS-376	1978	1983-06-18			1140	563
	Palapa Pacific 1		HS-376	1980	1983-06-18			1200	692
			HS-376		1983-06-28			1200	709
			HS-376	1980	1983-07-28			1140	653
			HS-376		1983-09-22			1200	709
			HS-376	1980	1984-02-03			1200	692	Launched along Westar 6. PAM-D failed to ignite, Shuttle recovered the satellite. Was relaunched as Palapa B2R.
			HS-376		1984-02-03			1244	582	Launched along Palapa B2. PAM-D failed to ignite, Shuttle recovered the satellite. Was relaunched as AsiaSat 1.
	HGS 5		HS-376	1983	1984-08-30			1117	540
			HS-376	1980	1984-08-30			1140	653
			HS-376		1984-09-21			1200	709
	Satcom 4R Arabsat 1D		HS-376		1984-11-08			1140	634
	SBTS 1		HS-376	1982	1985-02-08			1195
	Nahuel I1 Brasil 1T		HS-376	1978	1985-04-12			1140	563
			HS-376	1982	1985-06-17			1140	647
			HS-376	1980	1985-06-17			1140	653
			HS-376	1982	1985-08-27			1250	654
			HS-376	1982	1985-11-27			1250	654
			HS-376	1982	1985-11-27			1140	647
	SBTS 2		HS-376	1982	1986-03-28			1195
			HS-376	1984	1987-03-20			1200	692
			HS-376	1982	1987-09-16			1250	696
			HS-376	1983	1988-09-08			1117	540
			HS-376	1987	1989-08-27			1250	660
			HS-376		1990-04-07			1244	582	Was Westar 6, but the launch on Space Shuttle failed. It was recovered and launched again as AsiaSat 1.
			HS-376		1990-04-13			1200	692	Was Palapa B2, but the launch on Space Shuttle failed. It was recovered and launched again as Palapa B2R.
			HS-376	1987	1990-08-18			1250	662
			HS-376		1990-11-15
			HS-376	1989	1992-03-14			1390	788
			HS-376		1992-05-14			1200	692
			HS-376	1989	1992-08-22			1390	788	Launch failure
			HS-376	1983	1992-10-12			1390	709
			HS-376L	1991	1993-12-18			1080	629
			HS-376	1992	1994-02-19			1390	788
			HS-376	1992	1994-07-21			1400	726
			HS-376W	1990	1994-08-10			1757	1052
			HS-376L	1991	1994-10-07			1080	629
			HS-376W	1990	1995-03-28			1757	1052
			HS-376	1994	1996-01-12			1450	886
			HS-376	1995	1996-05-24			1390	788
			HS-376	1995	1996-07-03			1400	726
	Chinasat-7 HGS 2		HS-376	1995	1996-08-18			1384	734	Launch failure
			HS-376	1994	1996-11-13			1450	886
			HS-376	1993	1997-04-16			1236	723
			HS-376HP	1995	1997-05-20			1467	853
			HS-376W	1995	1998-02-04			1757	1052
			HS-376	1993	1998-04-28			1236	723
			HS-376HP	1997	1998-06-10			1451	853
			HS-376HP	1997	1998-10-05			1465	815
			HS-376HP	1997	1998-11-22			1425	793
			HS-376W	1998	2000-08-17			1757	1052
			HS-376HP	1999	2000-12-20			1445	824
			HS-376HP	2000	2002-03-29			1514	908
			HS-376HP	2000	2003-09-27			1530	895

See also

• Boeing 601
• Boeing Satellite Development Center