Space Transportation System Technology I

"A man may die, nations may rise and fall, but an idea lives on." 

~John F. Kennedy~ 

Bapak Teddy Lesmana, MM., Ph.D. Mengunjungi Museum Dirgantara dan Antariksa di USA.

Perkembangan Teknologi Antariksa di Indonesia - Indonesia belum pernah terlibat secara langsung dalam eksplorasi ruang angkasa, tetapi Indonesia sebenarnya termasuk negara yang cukup disegani karena pengalamannya dalam mengeksploitasi teknologi keantariksaan. Saat penggunaan satelit bagi sebagian besar negara masih sangat jarang, Indonesia telah meluncurkan satelitnya yang pertama, Palapa A1 pada 9 Juli 1976. Ini mencatatkan Indonesia sebagai negara ketiga di dunia setelah AS dan Canada yang menggunakan satelit komunikasi domestiknya sendiri. Indonesia juga sudah memanfaatkan jasanya untuk meluncurkan satelit Palapa generasi kedua, Palapa B1, pada 19 Juni 1983.

• SPACE SHUTTLE PROGRAM

• SPACE SHUTTLE REQUIREMENTS

• LAUNCH SITES

• BACKGROUND AND STATUS

• MISSION PROFILE

• ABORTS

• RETURN TO LAUNCH SITE OVERVIEW

• TRANSATLANTIC LANDING ABORT OVERVIEW

• ABORT TO ORBIT OVERVIEW

• ABORT ONCE AROUND OVERVIEW

• CONTINGENCY ABORT OVERVIEW

• ORBITER GROUND TURNAROUND

ORBITER MANUFACTURING AND ASSEMBLY

OPERATIONAL IMPROVEMENTS AND MODIFICATIONS

• ORBITER

• ORBITAL MANEUVERING SYSTEM/REACTION CONTROL

• SYSTEM AC-MOTOR-OPERATED VALVES

• PRIMARY RCS MODS

• FUEL CELL MODS

• AUXILIARY POWER UNIT MODS

• MAIN LANDING GEAR

• NOSE WHEEL STEERING MODS

• THERMAL PROTECTION SYSTEM MODS

• WING MODIFICATION

• MIDFUSELAGE MODIFICATIONS

• GENERAL-PURPOSE COMPUTERS

• INERTIAL MEASUREMENT UNIT MODS

• CREW ESCAPE SYSTEM

• EMERGENCY EGRESS SLIDE

• 17-INCH ORBITER/EXTERNAL TANK DISCONNECTS

• SPACE SHUTTLE MAIN ENGINE MARGIN IMPROVEMENT PROGRAM

• SSME FLIGHT PROGRAM

• SOLID ROCKET MOTOR REDESIGN

• ORIGINAL VERSUS REDESIGNED SRM FIELD JOINT

• ORIGINAL VERSUS REDESIGNED SRM CASE-TO-NOZZEL JOINT

• NOZZLE

• FACTORY JOINT

• PROPELLANT

• IGNITION SYSTEM

• GROUND SUPPORT EQUIPMENT

• DESIGN ANALYSIS SUMMARY

• VERIFICATION/CERTIFICATION TEST

• NON-DESTRUCTIVE EVALUATION

• CONTINGENCY PLANNING

• INDEPENDENT OVERSIGHT

Indonesia sebenarnya memiliki potensi yang jarang dimiliki negara lain untuk mengembangkan teknologi antariksanya sendiri. Potensi itu berupa garis katulistiwa yang membentang di atasnya. Sekitar 13% dari garis katulistiwa berada di atas wilayah Indonesia. Dengan demikian, Indonesia tercatat sebagai negara pemilik garis katulistiwa yang terpanjang di dunia. Hal ini menjadikan wilayah Indonesia sebagai tempat yang sangat ideal untuk menjadi lokasi peluncuran roket pengangkut satelit. Peluncuran roket dari dekat garis katulistiwa akan lebih menghemat bahan bakar roket, dan karenanya lebih murah dari segi biaya.

Kontes Roket Indonesia (Korindo)

Roket merupakan salah satu wahana dirgantara yang memiliki makna startegis. Wahana ini mampu digunakan untuk melaksanakan misi perdamaian maupun pertahanan, misalnya sebagai:

Roket Peluncur Satelit (RPS), 

Roket penelitian cuaca, 

Roket kendali, 

Roket balistik dari : darat ke darat, darat ke udara dan udara ke udara. 

Dengan kata lain, roket juga bisa berfungsi sebagai peralatan untuk menjaga kedaulatan dan meningkatkan martabat bangsa, baik di darat, laut maupun di udara sampai dengan antariksa. 

Oleh karena itu, negara yang menguasai kemandirian teknologi peroketan dengan baik, akan disegani oleh negara- negara lain di seluruh dunia. Indonesia sebagai negara besar dan luas sudah sepatutnya dapat meraih kemandirian yang berkelanjutan dalam penguasaan teknologi roket. 

Oleh sebab itu diperlukan upaya yang terus menerus untuk mewujudkan kemandirian ini, salah satunya melalui usaha menumbuh kembangkan rasa cinta teknologi dirgantara, khususnya teknologi peroketan sejak dini, yakni dengan mengadakan Kompetisi Muatan Roket Indonesia tingkat perguruan tinggi (KOMURINDO) setiap tahun sebagai sarana pendidikan dan menarik minat, sekaligus untuk menyiapkan bibit unggul tenaga ahli peroketan, yang akan diikuti oleh mahasiswa seluruh perguruan tinggi di Indonesia. 

Diharapkan, kompetisi ini dapat meningkatkan kemampuan mahasiswa dalam merancang bangun teknologi peroketan pada bagian muatan roket; dari mulai mendesain, membuat, menguji fungsional sampai dengan melaksanakan uji terbang muatan roket, sesuai dengan perilaku roket peluncur muatan. 

Melalui pemahaman perilaku roket peluncur yang diterapkan pada persyaratan operasional muatan roket, mahasiswa akan mampu memahami teknologi peroketan, yang pada perkembangannya, muatan hasil rancang bangun mahasiswa ini dapat menjadi cikal bakal lahirnya satelit Indonesia hasil karya bangsa Indonesia secara mandiri, sedangkan roket peluncurnya, dalam sekala besar dan teknologi yang lebih canggih dapat dikembangkan menjadi Roket Peluncur Satelit. 

Disamping itu, Kompetisi roket ini juga dapat meningkatkan rasa persatuan dan nasionalisme mahasiswa khususnya serta masyarakat pada umumnya di bidang teknologi peroketan. Juga dapat memperpendek jarak perbedaan penguasaan iptek dirgantara dan memperluas penyebarannya diantara perguruan tinggi di seluruh Indonesia.

Kontes Muatan Roket Indonesia 2011 





Kegiatan Korindo 2010

"Dari 38 perguruan tinggi ini terdapat 40 tim yang masing-masing akan menampilkan kemampuan fungsial muatan roket," kata Penanggung Jawab Teknis Kompetisi Roket Indonesia (Korindo) ke-3 Dr. Rika Andiarti. 

Kompetisi Roket Indonesia 2010 diselenggarakan DP2M Ditjen Dikti bekerja sama dengan Lembaga Penerbangan dan Antariksa Nasional (Lapan), Universitas Gadjah Mada, Pemkab Bantul dan Akademi Angkatan Udara.

Dewan juri Kompetisi Roket Indonesia 2010 terdiri dari lima orang, yaitu Dr. Ing. Agus Nuryanto (Lapan), Dr. Endra Pitowarno (PENS-ITS), Dr. Indrawanto (ITB), Dr. Wahidin Wahab (UI), Dr. Heru Susanto (UGM).

Sains Rocket

A rocket is a missile, spacecraft, aircraft or other vehicle that obtains thrust from a rocket engine. In any and all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction. Rocket engines push rockets forward simply by throwing their exhaust backwards extremely fast.

While comparatively inefficient for low speed use, rockets are relatively lightweight and powerful, capable of generating large accelerations and of attaining extremely high speeds with reasonable efficiency. Rockets are not reliant on the atmosphere and work very well in space.

Rockets for military and recreational uses date back to at least 13th century China. Significant scientific, interplanetary and industrial use did not occur until the 20th century, when rocketry was the enabling technology of the Space Age, including setting foot on the moon. Rockets are now used for fireworks, weaponry, ejection seats, launch vehicles for artificial satellites, human spaceflight, and space exploration.

Chemical rockets are the most common type of rocket and they typically create their exhaust by the combustion of rocket propellant. Chemical rockets store a large amount of energy in an easily released form, and can be very dangerous. However, careful design, testing, construction and use minimizes risks.

Reaktor Nuklir untuk Aplikasi Antariksa

"Everything is becoming science fiction. From the margins of an almost invisible literature has sprung the intact reality of the 20th century."
 ~J. G. Ballard, 1930.~

The Martian Surface Reactor: An Advanced Nuclear Power Station for Manned Extraterrestrial Exploration

A. Bushman, D.M. Carpenter, T.S. Ellis, S.P. Gallagher, M.D. Hershcovitch, M.C. Hine, E.D. Johnson, S.C. Kane, M.R. Presley, A.H. Roach, S. Shaikh, M.P. Short, and M.A. Stawicki




Add and Edited By:

Arip Nurahman
Department of Physics, Faculty of Sciences and mathematics
Indonesian University of Education
and
Follower Open Course Ware at MIT-Harvard University. M.A. USA.

Abstract

As part of the 22.033/22.33 Nuclear Systems Design project, this group designed a100 kWe Martian/Lunar surface reactor system to work for 5 EFPY in support of extraterrestrial human exploration efforts. The reactor design was optimized over the following criteria: small mass and size, controllability, launchability/accident safety, and high reliability. The Martian Surface Reactor was comprised of four main systems: the core, power conversion system, radiator and shielding.

The core produces 1.2 MWth and operates in a fast spectrum. Li heat pipes cool the core and couple to the power conversion system. The heat pipes compliment the chosen pin-type fuel geometry arranged in a tri-cusp configuration. The reactor fuel is UN (33.1w/o enriched), the cladding and structural materials in core are Re, and a Hf vessel encases the core. The reflector is Zr3Si2, chosen for its high albedo. Control is achieved by rotating drums, using a TaB2 shutter material. Under a wide range of postulated accident scenarios, this core remains sub-critical and poses minimal environmental hazards.

The power conversion system consists of three parts: a power conversion unit, a transmission system and a heat exchanger. The power conversion unit is a series of cesium thermionic cells, each one wrapped around a core heat pipe. The thermionic emitter is Re at 1800 K, and the collector is molybdenum at 950 K. These units, operating at 10+% efficiency, produce 125 kWe DC and transmit 100 kWe AC. The power transmission system includes 25 separate DC-to-AC converters, transformers to step up the transmission voltage, and 25 km of 22 gauge copper wire for actual electricity transmission. The remaining 900 kWth then gets transmitted to the heat pipes of the radiator via an annular heat pipe heat exchanger that fits over the thermionics. This power conversion system was designed with much redundancy and high safety margins; the highest percent power loss due to a single point failure is 4%.

The radiator is a series of potassium heat pipes with carbon-carbon fins attached. For each core heat pipe there is one radiator heat pipe. The series of heat pipe/fin combinations form a conical shell around the reactor. There is only a 10 degree temperature drop between the heat exchanger and radiator surface, making the radiating temperature 940 K. In the radiator, the maximum cooling loss due to a single point failure is less than 1%.

The shielding system is a bi-layer shadow shield that covers an 80º arc of the core. The inner layer of the shield is a boron carbide neutron shield; the outer layer is a tungsten gamma shield. The tungsten shield is coated with SiC to prevent oxidation in the Martian atmosphere. At a distance of 11 meters from the reactor, on the shielded side, the radiation dose falls to an acceptable 2 mrem/hr; on the unshielded side, an exclusion zone extends to 14 m from the core. The shield is movable to protect crew no matter the initial orientation of the core.

When combined together, the four systems comprise the MSR. The system is roughly conical, 4.8 m in diameter and 3 m tall. The total mass of the reactor is 6.5 MT.

Nuclear Reactors for Space Applications 

With the renewed interest in deep space applications, Professor A. Kadak has instituted several studies on nuclear power systems for space applications using the nuclear engineering design course offered for both graduate and undergraduate students. The first such study considered the design of nuclear electric power for propulsion and a terrestrial power station for manned Mars missions. This project was presented to NASA senior project planners in Washington DC in 2003.

Following that meeting and a subsequent meeting with Naval Reactors engineers, feedback was used to redesign the reactor from a highly efficient spent fuel Plutonium core to a highly enriched uranium core by a Master’s thesis student. This year, due to President Bush’s desire to test the new concepts on the Moon, a terrestrial 100 kwe plant was redesigned for use on both Mars and the Moon in the design project in the fall of 2004. As a result of these projects, the nuclear engineering department is gaining valuable experience in nuclear space applications.

Publications

Nuclear Space Applications (NSA) Program

Abstract	MIT-NSA-TR-001	V. Dostal, K. Gezelius, J. Horng, J. Koser, J.P. Iv, E. Shwageraus, P. Yarsky, and A.C. Kadak, "Mission to Mars: How to Get People There and Back with Nuclear Energy" (September 2004).
Abstract	MIT-NSA-TR-002	P. Yarsky, A.C. Kadak, and M.J. Driscoll, "Design of a Sodium-cooled Epithermal Long-term Exploration Nuclear Engine" (September 2004).
Abstract	MIT-NSA-TR-003	A. Bushman, D.M. Carpenter, T.S. Ellis, S.P. Gallagher, M.D. Hershcovitch, M.C. Hine, E.D. Johnson, S.C. Kane, M.R. Presley, A.H. Roach, S. Shaikh, M.P. Short, and M.A. Stawicki, "The Martian Surface Reactor: An Advanced Nuclear Power Station for Manned Extraterrestrial Exploration" (December 2004).

"Aplikasi IPTEK NUKLIR dalam Penjelajahan Angkasa Luar, Akan menjadi Power Utama"

~Arip~

Sources:

1.MIT Nuclear Space Research
2.SPACE POWER REACTORS
3.Nuclear Reactors for Space

Space Power Reactors

"Manusia harus segera bekerjasama untuk membangun sebuah alat bertenaga nuklir untuk melintasi tapal batas langit"

~Arip Nurahman~

This EOE article is adapted from an information paper published by the World Nuclear Association (WNA). WNA information papers are frequently updated, so for greater detail or more up to date numbers, please see the latest version on WNA website.

http://www.world-nuclear.org

 

Radioisotope Systems

So far, radioisotope thermoelectric generators (RTGs) have been the main power source for US space work over more than 40 years, since 1961. The high decay heat of plutonium-238 (²³⁸Pu) (0.56 W/g) enables its use as an electricity source in the RTGs of spacecraft, satellites, navigation beacons, etc. Heat from the oxide fuel is converted to electricity through static thermoelectric elements (solid-state thermocouples), with no moving parts. RTGs are safe, reliable and maintenance-free, and can provide heat or electricity for decades under very harsh conditions, particularly where solar power is not feasible.

Thus far, 45 RTGs have powered 25 US space vehicles including Apollo, Pioneer, Viking, Voyager, Galileo, Ulysses and New Horizons space missions as well as many civil and military satellites. The Cassini spacecraft carries three RTGs providing 870 watts of power en route to Saturn. Voyager spacecraft which have sent back pictures of distant planets have already operated for over 20 years and are expected to send back signals powered by their RTGs for another 15-25 years. The Viking and Rover landers on Mars depended on RTG power sources, as will the Mars Rovers to be launched in 2009.

The latest RTG is a 290 watt system known as the GPHS RTG. The thermal power source for this system is the General Purpose Heat Source (GPHS). Each GPHS contains four iridium-clad ²³⁸Pu fuel pellets, stands 5 cm tall, 10 cm square and weighs 1.44 kg. Eighteen GPHS units power one GPHS RTG. The Multi-Mission RTG (MMRTG), a current research focus, will use 8 GPHS units producing 2 kW that can then be used to generate 100 watts of electricity. 

The Stirling Radioisotope Generator (SRG) is based on a 55-watt electric converter powered by one GPHS unit. The hot end of the Stirling converter reaches 650°C and heated helium drives a free piston reciprocating in a linear alternator, heat being rejected at the cold end of the engine. The AC is then converted to 55 watts direct current (DC). This Stirling engine produces about four times as much electric power from the plutonium fuel than an RTG. Thus each SRG will utilize two Stirling converter units with about 500 watts of thermal power supplied by two GPHS units and will deliver 100-120 watts of electric power. The SRG has been extensively tested but has not yet flown. 

Russia has also developed RTGs using polonium-210—two are still in orbit on 1965 Cosmos navigation satellites. But Russian research was primarily focused on fission reactors for space power systems. In addition to RTGs, Radioactive Heater Units (RHUs) are used on satellites and spacecraft to keep instruments warm enough to function efficiently. Their output is only about one watt and they mostly use ²³⁸Pu—typically about 2.7g. Dimensions are about 3 cm long and 2.5 cm diameter, weighing 40 grams. Some 240 have been used so far by the US and two are in shut-down Russian Lunar Rovers on the moon. There will be eight on each of the US Mars Rovers launched in 2003. 

Both RTGs and RHUs are designed to survive major launch and re-entry accidents intact, as is the SRG.

Fission Systems: Heat

Over 100 kWe, fission systems have a distinct cost advantage over RTGs.

The US SNAP-10A launched in 1965 was a 45 kWt thermal nuclear fission reactor that produced 650 watts using a thermoelectric converter and operated for 43 days; it was shut down due to a satellite (not reactor) malfunction but remains in orbit today. 

The last US space reactor initiative was a joint NASA-DOE-Defence Department program developing the SP-100 reactor—a 2 MWt fast reactor unit and thermoelectric system delivering up to 100 kWe as a multi-use power supply for orbiting missions or as a lunar/Martian surface power station. This was terminated in the early 1990s after absorbing nearly US$1 billion. The design used uranium nitride fuel and was lithium-cooled. 

There was also a Timberwind pebble bed reactor (PBR) concept under the Defence Department Multi-Megawatt (MMW) space power program during the late 1980s, in collaboration with Department of Energy (DOE). This had power requirements well beyond any civil space program. 

Between 1967 and 1988, the former Soviet Union launched 31 low-powered fission reactors in Radar Ocean Reconnaissance Satellites (RORSATs) on Cosmos missions. They utilized thermoelectric converters to produce electricity, as with the RTGs. Romashka reactors were their initial nuclear power source, a fast spectrum graphite reactor with 90%-enriched uranium carbide fuel operating at high temperature. The Bouk fast reactor then produced 3 kW for up to 4 months. Later reactors, such as on Cosmos-954 that re-entered over Canada in 1978, had uranium-molybdenum fuel rods and a layout similar to the US heatpipe reactors described below. 

These designs were followed by the Topaz reactors with thermionic conversion systems, generating about 5 kWe of electricity for on-board uses. This was a US idea developed during the 1960s in Russia. In Topaz-2, each fuel pin (96% enriched uranium dioxide (UO₂)), sheathed in an emitter, is surrounded by a collector that form the 37 fuel elements which penetrate the cylindrical ZrH moderator. This in turn is surrounded by a beryllium neutron reflector containing 12 rotating control drums. NaK (a sodium-potassium alloy) coolant surrounds each fuel element. 

Topaz-1 was flown in 1987 on Cosmos 1818 and 1867. It was capable of delivering power for 3-5 years for ocean surveillance. Later Topaz designs were aiming for 40 kWe via an international project, undertaken largely in the USA starting in 1990. Two Topaz-2 reactors (without fuel) were sold to the USA in 1992. Budget restrictions in 1993 forced cancellation of a Nuclear Electric Propulsion Spaceflight Test Program associated with this reactor design.


Fission Systems: Propulsion

For spacecraft propulsion, once launched, some experience has been gained with nuclear thermal propulsion systems (NTR), that are said to be well-developed and proven. Nuclear fission heats a hydrogen propellant that is stored as liquid in cooled tanks. The hot gas (about 2500°C) is expelled through a nozzle to give thrust that may be augmented by injection of liquid oxygen into the supersonic hydrogen exhaust; this is more efficient than chemical reactions. Bimodal versions will run electrical systems on board a spacecraft, including powerful radars, as well as provide propulsion. Compared with nuclear electric plasma systems, these have much more thrust for shorter periods and can be used for launches and landings. 

However, attention is now turning to nuclear electric systems, where nuclear reactors are a heat source for electric ion drives, expelling plasma out of a nozzle to propel spacecraft already in space. Superconducting magnetic cells ionize hydrogen or xenon, heat it to extremely high temperatures (millions °C), accelerate it and expel it at very high velocity (e.g., 30 km/sec) to provide thrust. Research on one version, the Variable Specific Impulse Magnetoplasma Rocket (VASIMR), draws on that for magnetically-confined fusion power (tokamak) for electricity generation, but here the plasma is deliberately leaked to give thrust. The system works most efficiently at low thrust (that can be sustained), with small plasma flow, but high thrust operation is possible. The design is very efficient, with 99% conversion of electric to kinetic energy.

Sources:

1. Poston, D.I. 2002, Nuclear design of SAFE-400 space fission reactor, Nuclear News, Dec 2001.
2. Poston, D.I. 2002, Nuclear design of HOMER-15 Mars surface fission reactor, Nuclear News, Dec 2001.
3. Vrillon et al, 1990, ERATO article, Nuclear Europe Worldscan 11-12, 1990.
4. US DOE web site- space applications.
5. space.com 21/5/00, 16/6/00, 22/7/00, 17/1/03, 7/2/03.
6. www.nuclearspace.com
7. Delovy Mir 8/12/95.
8. G. Kulcinski, University of Wisconsin material on web.
9. Kleiner K. 2003, Fission Control, New Scientist 12/4/03.

10. OECD 1990, Emergency Preparedness for Nuclear-Powered Satellites.
11. NASA web site

Space Power Reactors

"Suatu hari nanti Umat manusia akan menyinggahi tempat-tempat asing dan Nuklir akan membawa mereka"

~Arip Nurahman~

This EOE article is adapted from an information paper published by the World Nuclear Association (WNA). WNA information papers are frequently updated, so for greater detail or more up to date numbers, please see the latest version on WNA website (link at end of article).

Introduction:

After a gap of several years, there is a revival of interest in the use of nuclear fission power for space missions. While Russia has used over 30 fission reactors in space, the USA has flown only one the SNAP-10A (System for Nuclear Auxiliary Power) in 1965.

The SNAP-10A reactor. (Source:NASA)

From 1959-73, there was a US nuclear rocket program—the Nuclear Engine for Rocket Vehicle Applications (NERVA)—focused on nuclear power replacing chemical rockets for the latter stages of launches. NERVA used graphite-core reactors, heating hydrogen and expelling it through a nozzle. Some 20 engines were tested in Nevada and yielded thrust up to more than half that of the space shuttle launchers. Since then, "nuclear rockets" have been about space propulsion, not launches. The successor to NERVA is today's nuclear thermal rocket (NTR). 

Another early idea was the US Project Orion, which would launch a substantial spacecraft from the Earth using a series of small nuclear explosions to propel it. The project commenced in 1958 and was aborted when the Atmospheric Test Ban Treaty of 1963 made it illegal, but radioactive fallout could have been a major problem. The Orion idea is still alive as other means of generating the propulsive pulses are considered.

* Radioisotope power sources have been an important source of energy in space since 1961.

* Fission power sources have been used mainly by Russia, but new and more powerful designs are under development in the USA.

After a gap of several years, there is a revival of interest in the use of nuclear fission power for space missions.

While Russia has used over 30 fission reactors in space, the USA has flown only one - the SNAP-10A (System for Nuclear Auxiliary Power) in 1965.

Early on, from 1959-73 there was a US nuclear rocket program - Nuclear Engine for Rocket Vehicle Applications (NERVA) which was focused on nuclear power replacing chemical rockets for the latter stages of launches. NERVA used graphite-core reactors heating hydrogen and expelling it through a nozzle. Some 20 engines were tested in Nevada and yielded thrust up to more than half that of the space shuttle launchers. Since then, "nuclear rockets" have been about space propulsion, not launches. The successor to NERVA is today's nuclear thermal rocket (NTR).

Another early idea was the US Project Orion, which would launch a substantial spacecraft - about 1000 tonnes - from the earth using a series of small nuclear explosions to propel it. The project was commenced in 1958 by General Atomics and was aborted in 1963 when the Atmospheric Test Ban Treaty made it illegal, but radioactive fallout could have been a major problem. The Orion idea is still alive, as other means of generating the propulsive pulses are considered.

Radioisotope Systems - RTGs

So far, radioisotope thermoelectric generators (RTGs) have been the main power source for US space work over nearly 50 years, since 1961. The high decay heat of Plutonium-238 (0.56 W/g) enables its use as an electricity source in the RTGs of spacecraft, satellites, navigation beacons, etc and its alpha decay process calls for minimal shielding. Heat from the oxide fuel is converted to electricity through static thermoelectric elements (solid-state thermocouples), with no moving parts. RTGs are safe, reliable and maintenance-free and can provide heat or electricity for decades under very harsh conditions, particularly where solar power is not feasible.

So far 45 RTGs have powered 25 US space vehicles including Apollo, Pioneer, Viking, Voyager, Galileo, Ulysses and New Horizons space missions as well as many civil and military satellites. The Cassini spacecraft carries three RTGs providing 870 watts of power as it explores Saturn. Voyager spacecraft which have sent back pictures of distant planets have already operated for over 20 years and are expected to send back signals powered by their RTGs for another 15-25 years. Galileo, launched in 1989, carried a 570 watt RTG. The Viking and Rover landers on Mars in 1975 depended on RTG power sources, as will the 900 kg Mars Science Laboratory Rover due to be launched in 2011 (the two Mars Rovers operating 2004-09 use solar panels and batteries).

The latest RTG is a 290 watt system known as the GPHS RTG. The thermal power for this system is from 18 General Purpose Heat Source (GPHS) units. Each GPHS contains four iridium-clad Pu-238 fuel pellets, stands 5 cm tall, 10 cm square and weighs 1.44 kg. The Multi-Mission RTG (MMRTG) will use 8 GPHS units producing 2 kW thermal which can be used to generate some 110 watts of electric power. It is a focus of current research and will be used in the Mars Science Laboratory, which will be a large mobile laboratory, the rover Curiosity, which is about five times the mass of previous Mars rovers.

The Stirling Radioisotope Generator (SRG) is based on a 55-watt electric converter powered by one GPHS unit. The hot end of the Stirling converter reaches 650°C and heated helium drives a free piston reciprocating in a linear alternator, heat being rejected at the cold end of the engine. The AC is then converted to 55 watts DC.

This Stirling engine produces about four times as much electric power from the plutonium fuel than an RTG. Thus each SRG will utilise two Stirling converter units with about 500 watts of thermal power supplied by two GPHS units and will deliver 100-140 watts of electric power from about 1 kg Pu-238. The SRG and Advanced SRG have been extensively tested but has not yet flown. NASA plans to use two ASRGs for its probe to Saturn's moon Titan (Titan Mare Explorer - TiME) or that to the comet Wirtanen.

Russia has developed RTGs using Po-210, two are still in orbit on 1965 Cosmos navigation satellites. But it concentrated on fission reactors for space power systems.

As well as RTGs, Radioactive Heater Units (RHUs) are used on satellites and spacecraft to keep instruments warm enough to function efficiently. Their output is only about one watt and they mostly use Pu-238 - typically about 2.7g of it. Dimensions are about 3 cm long and 2.5 cm diameter, weighing 40 grams. Some 240 have been used so far by USA and two are in shut-down Russian Lunar Rovers on the moon. Each of the US Mars Rovers which landed in 2004 uses eight of them to keep the batteries functional.

The Idaho National Laboratory's (INL) Centre for Space Nuclear Research (CSNR) in collaboration with NASA is developing an RTG-powered hopper vehicle for Mars exploration. When stationary the vehicle would study the area around it while slowly sucking up carbon dioxide from the atmosphere and freezing it, after compression by a Stirling engine.

Meanwhile a beryllium core would store heat energy required for the explosive vaporisation needed for the next hop. When ready for the next hop, nuclear heat would rapidly vaporise the carbon dioxide, creating a powerful jet to propel the craft up to 1000 metres into the 'air'.

A small hopper could cover 15 km at a time, repeating this every few days over a ten-year period. Hoppers could carry payloads of up to 200 kg and explore areas inaccessible to the Rovers. INL suggests that a few dozen hoppers could map the Martian surface in a few years, and possibly convey rock samples from all over the Martian surface to a craft that would bring them to Earth.

Both RTGs and RHUs are designed to survive major launch and re-entry accidents intact, as is the SRG.

Sources:

1. Poston, D.I. 2002, Nuclear design of SAFE-400 space fission reactor, Nuclear News, Dec 2001.
2. Poston, D.I. 2002, Nuclear design of HOMER-15 Mars surface fission reactor, Nuclear News, Dec 2001.
3. Vrillon et al, 1990, ERATO article, Nuclear Europe Worldscan 11-12, 1990.
4. US DOE web site- space applications.
5. Space.com 21/5/00, 16/6/00, 22/7/00, 17/1/03, 7/2/03.
6. www.nuclearspace.com
7. Delovy Mir 8/12/95.
8. G. Kulcinski, University of Wisconsin material on web.
9. Kleiner K. 2003, Fission Control, New Scientist 12/4/03.

10. OECD 1990, Emergency Preparedness for Nuclear-Powered Satellites.
11.  NASA web site

Examples of Spacecraft

"Pengembangan dan Riset Pesawat Ruang Angkasa Harus Kita Galakan"
 ~Arip~

Main article: List of spacecraft

Manned spacecraft

See also: Human spaceflight

Orbital

See also: Orbital spaceflight

The Apollo 15 Command/Service Module as viewed from the Lunar Module on August 2, 1971.

A Russian Soyuz bringing a crew to the ISS

• Apollo Spacecraft
• Gemini Spacecraft
• International Space Station
• Mercury Spacecraft
• Manned Maneuvering Unit - world's smallest manned spacecraft
• Mir
• Salyut
• Shuttle Buran
• Shenzhou Spacecraft
• Skylab
• Soyuz Spacecraft
• Space Shuttle
• Voskhod Spacecraft
• Vostok Spacecraft

Suborbital

See also: Suborbital spaceflight

• SpaceShipOne (commercial) suborbital
• X-15 suborbital

Sumber:

1. Wikipedia
2. http://astrophysicsblogs.blogspot.com/2008/09/25.html