Index

CHAPTER 6

ENVIRONMENT AND LOADS

6.1 Summary

This chapter introduces the natural environment of launch site, thermal environment during Payload operation, electromagnetic environment during launch preparation and LV flight, as well as thermal environments, mechanical environments (vibration, shock & noise) during LV flight.

6.2 Pre-launch Environments

6.2.1 Natural Environment

LM-2C can be launched in the three launch sites, JSLC, XSLC & TSLC. The natural environmental data in these three sites concluded by long-term statistic research. The environmental data in JSLC are emphasized as listed below.

Month

Highest (° C)

Lowest (° C)

Mean (° C)

January

14.20

-32.40

-11.20

February

17.70

-33.10

-6.20

March

24.10

-21.90

1.90

April

31.60

-13.60

11.10

May

38.10

-5.60

19.10

June

40.90

5.00

24.60

July

42.80

9.70

26.50

August

40.60

7.70

24.60

September

36.40

-4.60

17.60

October

30.10

-14.50

8.30

November

22.10

-27.50

-1.70

December

16.00

-34.00

-9.60

6.2.2 Payload Processing Environment

Payload will be checked, tested in Payload Processing Buildings (BS2 and BS3) and then transported to the launch pad for launch. The environment impacting Payload includes 3 phases: (1) Processing in BS2 and BS3; (2) Transportation from BS3 to launch pad; (3) preparation on launch tower.

6.2.2.1 Environment of Payload in Processing Building

The satellite will be tested and fueled in the BS2 and BS3 which are equipped with air conditioning system. The temperature, humidity and cleanness can be guaranteed in the whole process. Refer to chapter 7.

6.2.2.2 Environment of Payload during Transportation to Launch Tower

After finishing fairing encapsulation in BS3, the fairing/payload combination will be transported to launch pad. The environment for Payload during transportation can be assured by temperature-control measures (such as thermal blanket). The environmental parameters in fairing are as follows:

Temperature: 10° C~25° C

Relative humidity: 30%~60%

Cleanliness: 100,000 level

6.2.2.3 Air-conditioning inside Fairing at Launch Pad

The fairing air-conditioning system, shown in Figure 6-1, will be started after the payload was mated to the launch vehicle. The typical air-conditioning parameters inside the fairing are as follows:

Temperature: 15° C~22° C

Relative Humidity: 30%~45%

Cleanliness: 100,000 level

Air Flow Rate: 23~91kg/min

The air-conditioning is shut off at L-45 minutes and would be recovered in 40 minutes if the launch aborted.

 

Figure 6-1 Fairing Air-conditioning on the Launch Tower

The SC battery cooling system can also be provided with the following typical parameters:

Temperature: 10° C~16° C

Relative Humidity: 30%~60%

Cleanliness: 100,000 level

Air Flow Rate: >1.36kg/min

Relative pressure: <35Kpa

 

6.2.3 Electromagnetic Environment

6.2.3.1 On-board Radio Equipment

Characteristics of on-board radio equipment are shown below:

EQUIPMENT

FREQUENCY

(MHz)

POWER

(W)

susceptibility (dBW)

Polarization

Antenna position

Telemetry Transmitter 1

2200~2300

10

 

linear

Stage-2 Inter-tank section

Telemetry Transmitter 2

2200~2300

3x2

 

linear

SD

Beacon

5300~5400(down)

5650~5850(up)

1.5

-110

 

Stage -2 Inter-tank

section

Transponder

Rec.5550~56500.8us,800bit

0.8m s,

800bit

-91

linear

Stage -2 Inter-tank

section

Beacon

2750~2800

1

 

linear

Stage-2 Inter-tank

section

Telemetry command Receiver

600~700

 

-129

linear

Stage-2 Inter-tank

section

6.2.3.2 Electromagnetic Radiation Reduction

The payload is shielded by the launch tower and fairing. The electromagnetic strength is reduced 12dB at 0.1~10GHz comparing to the outside environment.

6.2.3.3 LV Electromagnetic Radiation and Susceptibility

The energy levels of launch vehicle electromagnetic radiation and susceptibility are measured at SC/LV separation plane. They are shown in Figure 6-2 to Figure 6-5.

 

 

Figure 6-2 Narrow Band Magnetic Emission from LM-2C

Figure 6-3 Narrow Band Electric Field Radiation from LM-2C

Figure 6-4 Broad Band Electric Field Radiation from LM-2C

Figure 6-5 Permissive Electric Field Radiation from LM-2C

 

 

6.2.3.4 EMC Analysis among Payload, LV and Launch Site

To conduct the EMC analysis among Payload, LV and launch site, both Payload and LV sides should provide related information to each other. The information provided by CALT are indicated in the Figure 6-2 to 6-5 in this chapter, while the information provided by SC side are as follows:

  1. Payload RF system configuration, characteristics, working period, antenna position and direction, etc.
  2. Values and curves of the narrow-band electric field of intentional and parasitic radiation generated by Payload RF system at Payload/LV separation plane and values and curves of the electromagnetic susceptibility accepted by Payload.

CALT will perform the preliminary EMC analysis based on the information provided by SC side, and both sides will determine whether it is necessary to request further information according to the analysis result.

6.2.3.5 Usage of SC RF Equipment

SC side and CALT will coordinate the RF working time phase during launch campaign and LV flight.

6.2.4 Contamination Control

The molecule deposition on Payload surface is less than 2mg/m2/week. The total mass loss is less than 1%. The volatile of condensable material is less than 0.1%.

6.3 Flight Environment

The mechanical environment for Payload is at Payload/LV interface. The pressure environment and thermal environment is just for typical fairing.

6.3.1 Pressure Environment

When the launch vehicle flies in the atmosphere, the fairing air-depressurization is provided by 12 vents (total venting area 350cm2) opened on the lower cylindrical section. The typical design range of fairing internal pressure is presented in Figure 6-6. The maximum depressurization rate inside fairing will not exceed 6.0 kPa/sec.

Figure 6-6 Fairing Internal Pressure vs. Flight Time

(Maximum Pressure depressurization rate Vs. time is 6.0kPa/sec.)

6.3.2 Thermal environment

The radiation heat flux density and radiant rate from the inner surface of the fairing is shown in Figure 6-7.

The free molecular heating flux at fairing jettisoning shall be lower than 1135W/m2. After fairing jettisoning, the thermal effects caused by the sun radiation, Earth infrared radiation and albedo will also be considered. The specific affects will be determined through the Payload/LV thermal coupling analysis by CALT.

Figure 6-7 Radiation Heat Flux Density and Radiant Rate

on the Inner Surface of Each Section of the Fairing

 

 

6.3.3 Static Acceleration

6.3.3.1 Longitudinal Static Acceleration

The longitudinal static acceleration is caused by the LV engine thrust and aerodynamic foresees. The acceleration is usually given in longitudinal static over load. The maximum overload is 4.6g for first stage flight and 6.7g for second stage flight, which could be varied slightly to different payloads.

6.3.3.2 Lateral Static Acceleration

The lateral static acceleration is caused by the LV maneuver and aerodynamic foresees. The maximum overload will not exceed 0.4g during the whole flight, which also could be varied slightly to different payloads.

6.3.4 Dynamic Environment

The LV suffers engine thrust, aerodynamic forces (including buffeting during transonic phase, wind aloft, etc.), various separation forces (such as stage-1/stage-2 separation, fairing jettisoning, SC/LV separation, etc.) during powered flight phase. It is also affected by disturbances caused by engine jet and transonic acoustic noise. According to the acting forces and LV responses, the dynamic environment can be divided into sinusoidal vibration, random vibration, shock and acoustic.

6.3.4.1 Sinusoidal Vibration

The sinusoidal vibration mainly occurs in the processes of engine ignition and shut-off, transonic flight and stage separations. The sinusoidal vibration (zero-peak value) at Payload/LV interface is shown below.

Direction

Frequency Range (Hz)

Amplitude or Acceleration

Two-stage LM-2C

LM-2C/CTS

Longitudinal

5 10

2 mm

2.5mm

10 100

0.8g

1.0 g

Lateral

5 10

1.5mm

1.75mm

10-100

0.6g

0.7g

6.3.4.2 Random Vibration

The Payload random vibration is mainly generated by noise and reaches the maximum at the lift-off and transonic flight periods.

The random vibration Power Spectral Density and the total Root-Mean-Square (RMS) values at Payload/LV separation plane in three directions are given in the table below.

Frequency Range (Hz)

Power Spectral Density

Total RMS Value

20 - 150

+3dB/octave.

6.94 g

150 - 800

0.04 g2/Hz

800 - 2000

-6 dB/octave.

 

6.3.4.3 Acoustic Noise

The flight noise mainly includes the engine noise and aerodynamic noise. The maximum acoustic noise Payload suffers occurs at the moment of lift-off and during the transonic flight phase. The values in the table below are the maximum noise levels in fairing.

Central Frequency of Octave Bandwidth (Hz)

Acoustic Pressure Level (dB)

31.5

118

63

131

125

134.5

250

135

500

133.5

1000

127

2000

122

4000

118

8000

114

Total Acoustic Pressure Level

140

0 dB referenced to 2´ 10-5 Pa.

6.3.4.4 Shock Environment

The maximum shock Payload suffers occurs at the Payload/LV separation. Different separation mechanism and preload forces will affect the separation shock significantly. The typical shock response spectrum at Payload/LV separation plane is shown bellow.

Frequency Range (Hz)

Response Acceleration (Q=10)

100-1500

+9.0 dB/octave.

1500-6000

4000 g

6.4 Load Conditions for Payload Design

6.4.1 Frequency Requirement

To avoid the Payload resonance with launch vehicle, the primary frequency of Payload structure should meet the following requirement (under the condition that the Payload is rigidly mounted on the LV separation plane.):

The frequency of the lateral main mode>12Hz

The frequency of the longitudinal main mode >35Hz

Whereas:

For Two-stage LM-2C, payload here means the SC.

For LM-2C/CTS, payload here means the SC plus CTS.

6.4.2 Loads Applied for Payload Structure Design

During LV flight, the Payload suffers four cases: the transonic phase or Maximum Dynamic Pressure phase, the first stage engines shut down, the first and second stage separation, and the second stage main engines shut down. Therefore, the following limit loads at SC/LV separation plane corresponding to different conditions in flight are recommended for Payload design consideration.

Flight Condition

Longitudinal Acceleration(g)

Lateral Acceleration(g)

Static

Dynamic

Combined

Transonic and MDP

+2.2

0.4

+2.6

1.0

Stage-1 shut down

+4.6

1.0

+5.6

0.6

Stage-1/2 separation

+0.8

3.0

+3.8/-2.2

0.8

Stage-2 shut down

+6.7

0.5

+7.2

0.4

Notes:

Payload design loads

=

Limit loads

´

Safety factor *

* The safety factor is determined by the Payload designer. (CALT suggests ³ 1.25).

6.4.3 Coupled Load Analysis

The Payload manufacturer should provide the Payload mathematical model to CALT for Coupled Loads Analysis (CLA). CALT will predict the Payload maximum dynamic response by coupled load analysis. The detailed data exchange requirements and special technical specifications will be coordinated by SC side and LV side.The Payload manufacturer should confirm that the Payload could survive from the predicted environment and has adequate safety margin.

 

6.5 Payload Qualification and Acceptance Test Specifications

6.5.1 Static Test (Qualification)

The main Payload structure must pass static qualification tests without damage. The test level must be not lower than Payload design load required in Paragraph 6.4.2.

6.5.2 Dynamic Environment Test

6.5.2.1 Sine Vibration Test

During tests, the Payload must be rigidly mounted on the shaker. The tables below specifies the vibration acceleration level (zero - peak) of Payload qualification and acceptance tests at Payload/LV interface. (See Figure 6-8a&b).

Frequency

(Hz)

Test Load

Acceptance

Qualification

For

LM-2C/CTS

Longitudinal

5-10

2.5 mm

4.0 mm

10-100

1.0 g

1.6 g

Lateral

5-10

1.75 mm

3.0 mm

10-100

0.7 g

1.2 g

Scan rate

 

4 Oct/min

2 Oct/min

For Two-stage LM-2C

Longitudinal

5-10

2.0 mm

3.25 mm

10-100

0.8 g

1.3 g

Lateral

5-10

1.5 mm

2.5 mm

10-100

0.6 g

1.0 g

Scan rate

 

4 Oct/min

2 Oct/min

Notes:

Figure 6-8a Sinusoidal Vibration Test in Longitudinal & lateral directions

(For LM-2C/CTS)

Figure 6-8b Sinusoidal Vibration Test in Longitudinal & lateral directions

(For Two-stage LM-2C)

6.5.2.2 Random Vibration Test

During tests, the Payload structure must be rigidly mounted onto the shaker. The table below specifies the Payload qualification and acceptance test levels at Payload/LV interface. (See Figure 6-9).

Frequency

(Hz)

Acceptance

Qualification

Spectrum Density

Total rms

(Grms)

Spectrum Density

Total rms

(Grms)

20 - 150

+3 dB/oct

6.94 g

+3 dB/oct

10.41 g

150 - 800

0.04 g2/Hz

0.09 g2/Hz

800 - 2000

-6 dB/octave.

-6 dB/octave

Duration

1 min.

2 min.

Notes:

Figure 6-9 Random Vibration Power Spectrum Density Test Conditions

(For Two-stage LM-2C and LM-2C/CTS in All Directions)

6.5.2.3 Acoustic Test

The acceptance and qualification test levels are given in the following table (also see Figure 6-10).

Central Octave Frequency (Hz)

Acceptance Sound

Pressure Level (dB)

Qualification Sound Pressure Level (dB)

Tolerance

(dB)

31.5

122

126

-2/+4

63

128

132

-1/+3

125

134

138

250

139

143

500

135

139

1000

130

134

2000

125

129

4000

120

124

-6/+4

8000

116

120

Total Sound

Pressure Level

142

146

-1/+3

0 dB is equal to 2´ 10-5 Pa.

Test Duration:

R Acceptance test: 1.0 minute

R Qualification test: 2.0 minutes

Figure 6-10 Payload Acoustic Test

6.5.2.4 Shock Test

The shock test level is specified in Paragraph 6.3.4.4. Such test shall be performed once for acceptance, and twice for qualification. A 6.0dB tolerance in test specification is allowed. However, the test strength must be applied so that in the shock response spectral analysis over 1/6 octave on the test results, 30% of the response acceleration values at central frequencies shall be greater than or equal to the values of test level. (See Figure 6-11)

The shock test can also be performed through Payload/LV separation test by using of flight Payload, payload adapter, and separation system. Such test shall be performed once for acceptance, and twice for qualification.

Frequency Range (Hz)

Shock Response Spectrum (Q=10)

100~1500

9.0 dB/oct.

1500~6000

4000g

Figure 6-11 Shock Response Spectrum at Payload/LV Separation Plane