Bussard Ramjet
SENIOR MEMBER
- Joined
- Nov 10, 2014
- Messages
- 3,978
- Reaction score
- 2
- Country
- Location
China’s Long March 3B Lofts Shijian-13 Satellite to Test High-Throughput Communications & Ion Drive
April 12, 2017
China’s Long March 3B rocket blasted off from the Xichang Satellite Launch Center on Wednesday, lifting into orbit the country’s first high-throughput communications satellite that is set for an experimental mission to test out electric propulsion and laser communications.
Lifting off from China’s Sichuan province at 11:04 UTC, 7:04 p.m. local time, Long March 3B was to turn to the south east to fly over the Chinese mainland before heading out over the Pacific Ocean for the standard half-hour ascent profile into a highly elliptical Geostationary Transfer Orbit. Official confirmation of launch success came forward through Chinese media around one hour after liftoff.
The 4,600-Kilogram satellite Long March 3B was carrying is known as Shijian-13 or ChinaSat-16 developed by the China Academy of Space Technology (CAST) and operated in a cooperation between CAST and communications provider ChinaSatcom. Shijian-13 was the original name of the satellite, flying under China’s space technology test program, while the ChinaSat-16 designation places it under the country’s state-controlled satellite communications program.
Shijian-13 carries the first high-throughput satellite (HTS) payload developed by China and it will test a new electric propulsion system for orbit-raising and stationkeeping in Geostationary Orbit.
The satellite hosts a broadband communications system operating in the Ka-Band frequency range and capable of a data throughput of 20gbps, making it the most powerful communications satellite sent into orbit by the Chinese. Shijian-13’s Ka-Band payload will provide 26 user beams covering the Chinese mainland and offshore areas, also delivering connectivity to airborne and maritime users as well as supporting emergency communications.
The satellite will deliver multimedia services and Internet connectivity with special focus on aeronautical services and China’s high-speed trains. Services delivered by the satellite will also be used for distance learning and telemedicine, connecting remote areas of the country.
Shijian-13 will take up station at 110.5 degrees East from where it can cover the entire Chinese territory as well as the Asia-Pacific Region.
In addition to its HTS payload, Shijian-13 is hosting a new electric propulsion system centered around the LIPS-200 ion engine developed by the Lanzhou Institute of Physics and first flight-tested on the Shijian-9A satellite in 2012.
Ion engines employ a heavy atomic species, typically Xenon, that is ionized, accelerated in an electric field and expelled at extremely high velocity – allowing the system to operate extremely efficiently in terms of the impulse achieved. Compared to conventional chemical rocket engines, ion engine systems offer a tenfold increase in specific impulse, but only reach a fraction of the thrust – making them suitable for in-orbit maneuvers over an extended time period whereas chemical propulsion is used for large changes in velocity in a short time span.
LIPS-200 – Image: Lanzhou Institute of Physics
Electric propulsion systems have the major benefit of increasing the payload mass a satellite is carrying or decreasing launch costs through reduction of spacecraft mass.
The LIPS-200 propulsion system comprises the ion thruster itself, a power processing unit, electric-propulsion control unit, Xenon tank, pressure regulation & flow control unit and a line connection unit. The overall mass of the system is 36 Kilograms, excluding the Xenon propellant.
The LIPS-200 ion thruster delivers a nominal thrust of 40 millinewtons at a specific impulse of 3136 seconds, requiring 1,200 Watts of electrical power during operation. Ground testing validated the design parameters of the engine over a 7500-hour operation period, but flight testing over several years in the operational space environment is necessary before declaring the system fully operational.
LIPS-200 Architecture – Image: Lanzhou Institute of Physics
On the Shijian-13 mission, LIPS-200 will be primarily used for stationkeeping in Geostationary Orbit. Stationkeeping is necessary due to perturbations in the satellite’s orbit caused by gravitational influences from Earth as well as solar pressure which, in combination, cause a GEO satellite to drift in the East-West direction and induce a North-South motion that would eventually place the satellite into an inclined orbit. East-West stationkeeping only requires 1.3m/s of delta-v per year and is almost negligible in propellant consumption when using conventional thrusters, however, North-South stationkeeping (NSSK) requires around 50m/s per year.
China outlined a plan to employ electric propulsion for NSSK to fully certify the technology and understand its capabilities before implementing it in other areas such as transfer from LEO to GEO and deep space exploration.
No information is available on the laser communications terminal reportedly carried by Shijian-13. China made a number of developments in this area in recent years, specifically the inauguration of ultra-secure quantum communications that are completed via optical laser terminals. Extending this technology from Low Earth Orbit to Geostationary Orbit would mark a major accomplishment in the country’s continuing drive in the area of quantum computing and communications.
Shijian-13 is based on the upgraded DFH-3B satellite platform with a bus size of 2.2 by 2.0 by 3.1 meters, capable of hosting payloads in the 500kg range. The bus includes six principal subsystems to provide a stable platform for the payload with the bus in charge of power generation & distribution, propulsion, attitude determination and control, thermal control and data handling. The three-axis stabilized platform has a nominal end-of-life power supply of 1,700 Watts and a life expectancy of at least 15 years.
Tasked with launching the Shijian-13 satellite was the Long March 3B/G2 (Y43) launch vehicle, weighing in at 456,000 Kilograms and standing 56.33 meters tall with a core diameter of 3.35 meters. The rocket comprises four boosters and a three-stage stack with the lower stages consuming hypergolic propellants, Unsymmetrical Dimethylhydrazine and Nitrogen Tetroxide while the third stage uses cryogenic propellants, Liquid Hydrogen and Liquid Oxygen.
Long March 3 thundered off at 11:04 UTC with a thrust of 604 metric ton-force, rising into the skies over the Xichang launch base in the Sichuan province in south-western China. After a vertical ascent of a few seconds, the rocket began to pitch and roll onto its planned ascent path, taking it south-east across China before passing over the Pacific Ocean.
With all engines firing at full throttle, Long March 3B/E burned 2,350 Kilograms of propellant per second as it started racing uphill and making its way downrange, passing Mach 1 and encountering Maximum Aerodynamic Pressure. Each of the four boosters delivered 75,500 Kilogram-force of additional thrust to the vehicle using a single DaFY-5-1 engine. The boosters consumed their propellant load of 41,200kg, each, over the course of a burn of 140 seconds after which they dropped away from the three-stage rocket.
With the boosters gone, the Core Stage continued powering the vehicle using a DaFY-6-1 cluster of four engines delivering 302 metric tons of thrust. Overall, the 24.8-meter tall first stage launched with a propellant load of 186,200 Kilograms that was expended in two minutes and 38 seconds. Immediately after engine cutoff of the first stage, the second stage commanded its four-chamber vernier engine to ignite as part of the hot-staging sequence employed by the Long March 3B.
A series of 14 pyrotechnic bolts were fired to disconnect the first and second stage, allowing the second stage’s four-chamber vernier engine to move the stack away from the empty core with a thrust of five tons. Moments after staging, the second stage ignited its DaFY-20-1 main engine, soaring up to a full thrust of 75,660 Kilogram-force to continue powered ascent. Overall, the second stage launched with a propellant load of 49,400 Kilograms measuring 12.92 meters in length and 3.35 meters in diameter.
While the second stage was firing, Long March 3B departed the dense atmosphere, making it safe to jettison the protective payload fairing and expose the Shijian-13 satellite for the rest of its ride uphill.
The second stage performed a nominal burn of 178 seconds with the vernier engine burning about six seconds longer than the main engine. Immediately after shutdown, the pyrotechnic stage separation system was initiated and solid-fueled retrorockets moved the second stage away.
One second after staging, the 12.4-meter long third stage ignited its two cryogenic YF-75 engines, generating a total thrust of 16,000 Kilogram-force as part of its initial burn to accelerate the stack to orbital velocity in order to enter a Low Earth Parking Orbit.
The Low Earth Parking orbit, around 190 Kilometers in altitude, was reached after a third stage burn of around four minutes and 45 seconds, marking the start of a coast phase. The coast phase, nearly 11 minutes in duration, was set up to allow the stack to fly to a position where the second burn could be performed around the equator passage so that the high-point of the orbit would be placed over the equator.
This second burn lasted for approximately three minutes and 15 seconds and was followed by a variable velocity adjustment that involved the vernier engines of the third stage which continued to fire until the navigation platform sensed that the targeted injection velocity was achieved, thus optimizing the accuracy of the orbital insertion with spacecraft separation occurring approximately 26 minutes after launch.
http://spaceflight101.com/long-march-3b-launches-shijian-13/
实践十三号的五宗“最”—让你永不失联
2017-04-12 CAST_CASC 中国空间技术研究院
实践十三号（中星16号）卫星的成功发射是建设航天强国的又一重要标志性成就，使中国卫星通信能力实现重大跨越。中国由此叩开通信卫星“高通量时代”的大门。
▲高通量卫星的技术特点
作为东方红三号B平台全配置首发星、我国首颗高通量通信卫星、我国首颗电推进工程化应用的卫星，实践十三号（中星16号）卫星在国内高轨卫星领域创造了五宗“最”。
01最先在我国卫星上应用Ka频段多波束宽带通信系统
通信总容量超过20Gbit/s,卫星将引领我国高通量卫星通信技术发展；可支持多用户、大容量双向载荷，在广大地区通过该卫星进行数据高速下载的同时，可支持大量用户高速上传数据。
▲高通量卫星系统和传统卫星通信系统对比
02最先实现在我国高轨卫星上使用电推进
东方红－3B卫星平台是我国研制的最新一代中等容量通信卫星平台，它采用了综合电子、电推进、高效热控、锂离子蓄电池等先进技术，这些技术可推广应用至其他平台，有效促进卫星平台能力，将实现我国卫星平台技术水平跨越式提升。
View attachment 390258
▲通信卫星事业部研制团队
电推进系统在无需消耗化学推进剂情况下就能够完成卫星全寿命期内南北位置保持任务，卫星可承载能力显著提升，功用更加强大。电推进是一种先进的空间推进技术，相对于传统的化学推进，具有高比冲、小推力、长寿命、高可靠等特点。在长寿命航天器上应用电推进能大幅减少推进剂的携带量，提高有效载荷比，延长航天器寿命。研究院就瞄准国际前沿，将电推进作为平台标准配置，抓总开展了大量的设计、仿真和分析。这对我国高轨卫星来说是具有革命性的技术突破，卫星承载能力显著提升。
▲兰州空间技术物理研究所的研究人员正装配电推力器
03最先在我国高轨卫星上搭载激光通信系统
由于激光通信具有高带宽、高传输速率优点，是满足大容量、高速率通信的重要手段之一，我院研制团队与哈尔滨工业大学等单位联合攻关，成功将激光通信系统应用于高通量卫星，相关技术指标达到国际先进水平。
▲实践十三号（中星16号）号运行原理图
04最先在我国卫星上把技术试验和示范应用相结合
作为我国首颗Ka宽带通信卫星，实践13号（中星16号）卫星在完成东方红－3B卫星平台和载荷新技术一系列在轨试验验证后，卫星将纳入“中星”卫星系列，被命名为中星16号卫星，开展Ka频段宽带通信系统的应用推广，提供双向宽带通信示范化运营服务，这样可加速科研成果的应用转化，既满足了新技术在轨试验的目的，又满足了载荷示范应用的要求，提高了工程综合效益。
▲高通量卫星的应用领域
05最先将我国地球静止轨道卫星发射窗口时间由凌晨提前至傍晚19点
在以往的卫星发射任务中，主要考虑卫星的安全余量，发射窗口时间通常选在凌晨零时左右。在实践十三号（中星16号）卫星发射窗口的确定过程中，研制团队充分研究了发射窗口提前所导致的地影时间增加、测控不可见弧段延长、变轨期间蓄电池放电等不利影响，并利用东方红三号B平台技术革新所带来的性能提升，制定了详细的飞行程序和预案，在新窗口下成功完成了发射任务，实现了卫星可在2个窗口时间选择发射的先例，同时也保证了工作人员的正常作息时间。本次发射标志着我国卫星发射及运营管理水平在多样化的道路上取得了长足进步。
▲实践十三号（中星16号）卫星成功发射
http://mp.weixin.qq.com/s/rmm2NXhN_Ie6ZwJblo_TVg
Just for reference here, ViaSat1 launched in 2011, has a throughput of 140Gb, compared with 20 Gb of this satellite in 2017.
It seems China is at least 2-3 generations behind the leading American commercial operators.
