P3D Launch Sequence Study (Part III)

Started: June 21, 1997 -- Last Update: July 1, 1997

Viktor Kudielka (ÖVSV P3D Mission Analysis Project)

Introduction

This document is intended as a base for discussion of alternative launch sequences of P3D. This part III considers the new launch schedules as well as changes of S/C and propellant masses.

Previous parts:
P3D Launch Sequence Study, Part I, Dec. 5, 1996,
P3D Launch Sequence Study, Part II, Feb. 12, 1997

Start Data

• Start date: Ariane flight AR502, September 30, 1997
• Launch window/actual start time: Ariane Standard Launch Window, first perigee at 12:40 UT (+/- 00:40) ??
• GTO data:
  • mean motion: 2.24859 orbits/day
  • eccentricity: .717
  • inclination: 7.763°
  • argument of perigee: 178.0°
  • longitude of ascending node(RAAN): depending on start date and time, 003.4° assumed
• Satellite Data:
  • dry mass: 300 - 400 kg actual
  • start mass: 550 - 650 kg actual
  • arc jet propellant(NH3): 51.8 kg max.
  • bi-propellant(MNH+N2O4): 192 kg max.
  • arc jet velocity: 4750 m/s
  • arc jet mass flow: 25 10^-6 kg/sec
  • 400 N motor velocity: 3000 m/s
  • bipropellant mass flow: .1333 kg/sec

Nominal DeltaV

• Assumptions:
  • dry mass: 356 kg
  • start mass: 600 kg
  • arc-jet propellant: 52 kg
  • bi-propellant: 192 kg
  • arc jet velocity: 4750 m/s
  • 400 N motor velocity: 3000 m/s
  • Efficiency: 1.0

1. Arc-jet first: 4750 ln(600/548) + 3000 ln(548/356) = 430.6 + 1294 = 1724.6 m/s
2. Bi-prop first: 3000 ln(600/408) + 4750 ln(408/356) = 1157 + 647.6 = 1804.6 m/s

Worst Case DeltaV

• Assumptions:
  • dry mass: 406 kg
  • start mass: 650 kg
  • arc-jet propellant: 52 kg
  • bi-propellant: 192 kg
  • arc jet velocity: 4750 m/s
  • 400 N motor velocity: 3000 m/s
  • Efficiency: 1.0

1. Arc-jet first: 4750 ln(650/598) + 3000 ln(598/406) = 396 + 1161.7 = 1557.7 m/s
2. Bi-prop first: 3000 ln(650/458) + 4750 ln(458/406) = 1050.3 + 572.4 = 1622.7 m/s

Scenario S1

This scenario serves as a demonstration only, since impulsive mamoeuvers are assumed exclusively. The ideal target argP=315° is reached after about 1 year. The inclination of 61° at RAAN=230° makes shure, that an ArgP= 315° +/- 15° is maintained for about 11 years. The apogee will stay much longer (> 25 years) over the northern hemisphere. The height of perigee will increase to 8000 km. Other start times or dates will cause a substantial different behaviour.

The following table presents details of the powered flight phase.

Orbit	ArgP	sma	ecc	inc	HeightPer	HeightApo	VPer	VApo	deltaV
#	deg	km		deg	km	km	m/s	m/s	m/s
001	178.00	24611	0.7175	07.76	575	35890	09922	1632	0000
003	178.66	24611	0.7174	07.77	577	35888	09920	1632	0000
003	178.66	32223	0.7841	07.77	577	51113	10111	1223	0191
008	180.16	32223	0.7838	07.78	589	51101	10102	1225	0000
009	180.14	32223	0.7838	39.81	590	51101	10102	1225	0676
570	270.16	32223	0.7842	38.30	577	51113	10112	1223	0000
571	315.02	32223	0.7841	61.25	579	51111	10110	1224	1073

Figures S1.1A and S1.1B show the whole period of powered flight. Figures S1.2A and S1.2B show the final drift phase.

Summary -- Scenario S1

• Start date September 30, 1997
• GTO RAAN = 3.4°
• Increasing orbital period to 16 hours (bi-prop, deltaV = 191 m/s)
• At ArgP = 180° inclination change by 32° to 39.8° (bi-prop, deltaV = 676 m/s)
• At ArgP = 270° rotation around major axis by 52° (bi-prop, deltaV = 1073 m/s)
• New orbit with ArgP = 315° and i = 61.25° after about one year
• Grand Total deltaV = 1939 m/s

Scenario T1

This scenario is an attempt to find a proper balance of bi-prop and arc-jet operation. In addition the required deltaV is kept low, by compromising on the trend of ArgP during the final drift phase and also on the time needed for the orbital manoeuvers. Arc-jet operation is assumed to be in one hour intervals around perigee. The reduced efficiency due to the misalignment of flight path and spin axis is not yet taken into account.

Orbit	ArgP	sma	ecc	inc	HeightPer	HeightApo	VPer	VApo	deltaV
#	deg	km		deg	km	km	m/s	m/s	m/s
0001	178.00	24611	0.7175	07.76	0575	35890	09922	1632	000
0008	180.28	24611	0.7172	07.77	0582	35883	09917	1633	000
0009	180.30	24611	0.7172	21.77	0583	35883	09916	1633	398
1709	270.02	51260	0.8686	21.82	0356	89409	10517	0739	420
1710	335.00	51260	0.8685	61.53	0363	89401	10511	0740	728
2060	337.23	32195	0.7705	64.15	1012	50621	09772	1267	229

Figures T1.1A and T1.1B show the whole period of powered flight. Figures T1.2A and T1.2B show the final drift phase.

Summary -- Scenario T1

• Start date September 30, 1997
• GTO RAAN = 3.4°
• At ArgP = 180° inclination change by 14° to 21.8° (bi-prop, deltaV = 398 m/s)
• Increasing orbital period to 32 hours (arc-jet, deltaV = 420 m/s, more than one full rotation of ArgP necessary)
• At ArgP = 270° rotation around major axis by 59° (bi-prop, deltaV = 728 m/s)
• Reducing orbital period to 16 hours (arc-jet, deltaV = 229 m/s)
• New orbit with ArgP = 337° and i = 64° after about 1600 days
• Total deltaV bi-prop = 1126 m/s
• Total deltaV arc-jet = 649 m/s
• Grand Total deltaV = 1776 m/s

Scenario T2

The major drawback of scenario T1 is the very long time for the initial orbital manoeuvers. When we insist on the major inclination change at the first occurence of ArgP = 270°, we have to use the bi-prop motor for increasing the orbital period. In order to minimize the necessary bi-prop mass, we drop the initial inclination increase (for adjusting the argP) alltogether and start with an apogee very near the equator. We have to increase the orbital period as much as possible (assuming 89000 km height of apogee is the maximum for reliable operation) in order to use the arc-jet after the major inclination change for reducing the period to 16 hours. Most probably we could terminate the spin mode already after 130 days.

The final drift period does not look very attractive, but since some propellant for the arc-jet might be left, we can investigate a further orbital refinement later.

Orbit	ArgP	sma	ecc	inc	HeightPer	HeightApo	VPer	VApo	deltaV
#	deg	km		deg	km	km	m/s	m/s	m/s
0001	178.00	24611	0.7175	07.76	0575	35890	09922	1632	000
0295	269.25	27400	0.7434	07.82	0654	41390	09941	1463	083
0297	269.88	51172	0.8626	07.82	0652	88937	10277	0758	334
0300	351.25	51172	0.8626	63.31	0652	88936	10277	0758	792
0528	352.59	32200	0.7892	63.69	0411	51232	10249	1208	223

Figures T2.1A and T2.1B show the whole period of powered flight. Figures T2.2A and T2.2B show the final drift phase.

Summary -- Scenario T2

• Start date September 30, 1997
• GTO RAAN = 3.4°
• Increasing orbital period to 32 hours (arc-jet: deltaV = 83 m/s, bi-prop: deltaV = 334 m/s)
• At ArgP = 270° rotation around major axis by 63° (bi-prop, deltaV = 792 m/s)
• Reducing orbital period to 16 hours (arc-jet, deltaV = 223 m/s)
• New orbit with ArgP = 352.6° and i = 63.7° after 370 days
• Total deltaV bi-prop = 1126 m/s
• Total deltaV arc-jet = 306 m/s
• Grand Total deltaV = 1432 m/s

Scenario T3

While T2 represents the attempt to reduce the elapsed time drastically, T3 demonstrates that a further reduction of the bi-pro deltaV requirements is possible. Arc-jet operations are assumed to last for one hour around perigee. ArgP is for a pretty long period near the equator, this is the price for the minimum bi-prop deltaV. Height of perigee is also low after the major inclination change. For an actual case some more refinements are necessary.

Orbit	ArgP	sma	ecc	inc	HeightPer	HeightApo	VPer	VApo	deltaV
#	deg	km		deg	km	km	m/s	m/s	m/s
0001	178.00	24611	0.7175	07.76	0575	35890	09922	1632	000
0129	218.63	27400	0.7442	07.83	0632	41412	09959	1461	083
0179	233.86	45279	0.8445	07.85	0661	77141	10220	0861	285
0322	270.00	51248	0.8666	07.77	0458	89281	10433	0746	049
0323	351.30	51248	0.8668	63.30	0450	89289	10439	0745	779
0551	353.44	32199	0.7940	62.58	0254	51388	10384	1192	221

Figures T3.1A and T3.1B show the whole period of powered flight. Figures T3.2A and T3.2B show the final drift phase.

Summary -- Scenario T3

• Start date September 30, 1997
• GTO RAAN = 3.4°
• Increasing orbital period to 32 hours (arc-jet: deltaV = 132 m/s, bi-prop: deltaV = 285 m/s)
• At ArgP = 270° rotation around major axis by 63° (bi-prop, deltaV = 779 m/s)
• Reducing orbital period to 16 hours (arc-jet, deltaV = 221 m/s)
• New orbit with ArgP = 353.4° and i = 62.6° after 470 days
• Total deltaV bi-prop = 1064 m/s
• Total deltaV arc-jet = 353 m/s
• Grand Total deltaV = 1417 m/s

Scenario T4

Scenario T4 uses the same strategy as T3 to go to a 32 hour orbit within the 90 degree drift of ArgP. Additionally there is a small (3 degrees) inclination change at ArgP = 180°, in order to get the apogee a little further north after the major inclination change. The size of this initial inclination change is restricted by the available mass of bi-propellant.

Orbit	ArgP	sma	ecc	inc	HeightPer	HeightApo	VPer	VApo	deltaV
#	deg	km		deg	km	km	m/s	m/s	m/s
0001	178.00	24611	0.7175	07.76	0575	35890	09922	1632	000
0008	180.28	24611	0.7172	07.77	0582	35883	09917	1633	000
0009	180.48	24611	0.7172	10.77	0583	35883	09916	1633	086
0126	217.06	27214	0.7424	10.81	0632	41040	09954	1471	078
0176	232.17	45286	0.8446	10.81	0658	77159	10223	0861	290
0314	270.13	51234	0.8669	10.65	0439	89273	10448	0745	049
0315	348.09	51234	0.8668	63.51	0447	89265	10441	0745	779
0538	349.99	32193	0.7899	62.82	0385	51245	10271	1205	222

Figures T4.1A and T4.1B show the whole period of powered flight. Figures T4.2A and T4.2B show the final drift phase.

Summary -- Scenario T4

• Start date September 30, 1997
• GTO RAAN = 3.4°
• At ArgP = 180° inclination change by 3° to 10.8° (bi-prop, deltaV = 86 m/s)
• Increasing orbital period to 32 hours (arc-jet: deltaV = 127 m/s, bi-prop: deltaV = 290 m/s)
• At ArgP = 270° rotation around major axis by 63° (bi-prop, deltaV = 779 m/s)
• Reducing orbital period to 16 hours (arc-jet, deltaV = 222 m/s)
• New orbit with ArgP = 350° and i = 62.8° after 455 days
• Total deltaV bi-prop = 1154 m/s
• Total deltaV arc-jet = 349 m/s
• Grand Total deltaV = 1503 m/s