Saturday, 11 June 2011

Indonesian Space Force Command

Indonesian Space Force Command
Komando 
Untuk Keamanan Luar Angkasa 
Dari Angkatan Antariksa Indonesia


“You cannot simultaneously prevent and prepare for war.”

 ~Albert Einstein~

F-35 Lightning II
Gray jet aircraft taking off on a clear blue sky, with the landing gear still protruding from its underside. Mountains make-up the background.
An F-35A Lightning II, marked AA-1, lands at Edwards Air Force Base, California
Role Stealth multirole fighter
National origin United States
Manufacturer Lockheed Martin Aeronautics
First flight 15 December 2006
Introduction 2016[1]-2018[2][3]
Status In limited production, undergoing flight testing
Produced 2006–present
Number built 13 flight-test aircraft[N 1]
Unit cost F-35A: US$122 million (flyaway cost, 2011)[6]
F-35B: US$150M (avg. cost, 2011)[7]
F-35C: US$139.5M (avg. cost, 2011)[7][8]
Note: Average costs excludes development cost[7]
F-35A weapons system unit cost is US$183.5M (FY 2011)[6]
Developed from Lockheed Martin X-35


The Lockheed Martin F-35 Lightning II is a family of single-seat, single-engine, fifth generation multirole fighters under development to perform ground attack, reconnaissance, and air defense missions with stealth capability.[9][10] The F-35 has three main models; one is a conventional takeoff and landing variant, the second is a short take off and vertical-landing variant, and the third is a carrier -based variant.

Design


F-35A being towed to its inauguration ceremony on 7 July 2006

F-35B's thrust vectoring nozzle and lift fan



The F-35 appears to be a smaller, slightly more conventional, single-engine sibling of the sleeker, twin-engine Lockheed Martin F-22 Raptor, and indeed drew elements from it. The exhaust duct design was inspired by the General Dynamics Model 200 design, which was proposed for a 1972 supersonic VTOL fighter requirement for the Sea Control Ship.[67] For specialized development of the F-35B STOVL variant, Lockheed consulted with the Yakovlev Design Bureau, purchasing design data from their development of the Yakovlev Yak-141 "Freestyle".[68][69] Although several experimental designs have been built and tested since the 1960s including the Navy's unsuccessful Rockwell XFV-12, the F-35B is to be the first operational supersonic, STOVL stealth fighter.[70]


The F-35 has a maximum speed of over Mach 1.6. With a maximum takeoff weight of 60,000 lb (27,000 kg),[N 3][72] the Lightning II is considerably heavier than the lightweight fighters it replaces. In empty and maximum gross weights, it more closely resembles the single-seat, single-engine Republic F-105 Thunderchief, which was the largest single-engine fighter of the Vietnam war era. However the F-35's modern engine delivers over 60 percent more thrust in an aircraft of the same weight so that in thrust to weight and wing loading it is much closer to a comparably equipped F-16.[N 4]

Acquisition deputy to the assistant secretary of the Air Force, Lt. Gen. Mark D. "Shack" Shackelford has said that the F-35 is designed to be America's "premier surface-to-air missile killer and is uniquely equipped for this mission with cutting edge processing power, synthetic aperture radar integration techniques, and advanced target recognition."[74][75]
Some improvements over current-generation fighter aircraft are:
  • Durable, low-maintenance stealth technology, using structural fiber mat instead of the high-maintenance coatings of legacy stealth platforms;[76]
  • Integrated avionics and sensor fusion that combine information from off and on board sensors to increase the pilot's situational awareness and improve target identification and weapon delivery, and to relay information quickly to other command and control (C2) nodes;
  • High speed data networking including IEEE 1394b[77] and Fibre Channel.[78]
  • The Autonomic Logistics Global Sustainment (ALGS), Autonomic Logistics Information System (ALIS) and Computerized Maintenance Management System (CMMS) help ensure aircraft uptime with minimal maintenance manpower.[79]
  • Electrohydrostatic actuators run by a power-by-wire flight-control system.[80]
Lockheed Martin claims the F-35 is intended to have close and long-range air-to-air capability second only to that of the F-22 Raptor.[9] The company has suggested that the F-35 could also replace the USAF's F-15C/D fighters in the air superiority role and the F-15E Strike Eagle in the ground attack role, but it does not have the range or payload of either F-15 model.[81] The F-35A does carry a similar air-to-air armament as the Boeing F-15SE Silent Eagle when both aircraft are configured for low observable operations and has over 80 percent of the larger aircraft's combat radius.[82]


The majority of the structural composites in the F-35 are made out of bismaleimide (BMI) and composite epoxy material.[83] However the F-35 will be the first mass produced aircraft to include structural nanocomposites, Carbon nanotube reinforced Epoxy.[84]


The F-35 program has learned from the corrosion problems that the F-22 had when it was first introduced in 2005. The F-35 uses a gap filler that causes less galvanic corrosion to the skin, is designed with fewer gaps in its skin that require gap filler, and has better drainage.[85]

A United States Navy study found that the F-35 will cost 30 to 40 percent more to maintain than current jet fighters.[86] And a Pentagon study found that it may cost $1 trillion to maintain the entire fleet over its lifetime.[87]

 

 Engines

The F-35's main engine is the Pratt & Whitney F135. The General Electric/Rolls-Royce F136 is being developed as an alternative engine.[88] The F135/F136 engines are not designed to supercruise in the F-35.[89] The STOVL versions of both power plants use the Rolls-Royce LiftSystem, patented by Lockheed Martin and built by Rolls-Royce. This system is more like the Russian Yak-141 and German VJ 101D/E than the preceding generation of STOVL designs,[90] such as the Harrier Jump Jet in which all of the lifting air went through the main fan of the Rolls-Royce Pegasus engine.[91]


The Lift System is composed of a lift fan, drive shaft, two roll posts and a "Three Bearing Swivel Module" (3BSM).[92] The 3BSM is a thrust vectoring nozzle which allows the main engine exhaust to be deflected downward at the tail of the aircraft. The lift fan is near the front of the aircraft and provides a counter-balancing thrust using two counter-rotating blisks.[93] It is powered by the engine's low-pressure (LP) turbine via a drive shaft and gearbox. Roll control during slow flight is achieved by diverting unheated engine bypass air through wing mounted thrust nozzles called Roll Posts.[94][95] Like lift engines, the added lift fan machinery increases payload capacity during vertical flight, but is dead weight during horizontal flight. The cool exhaust of the fan also reduces the amount of hot, high-velocity air that is projected downward during vertical take off, which can damage runways and aircraft carrier decks.[citation needed]

To date, F136 funding has come at the expense of other parts of the program, reducing the number of aircraft

built and increasing their costs.[96] The F136 team has claimed that their engine has a greater temperature margin which may prove critical for VTOL operations in hot, high altitude conditions.[97]

Pratt & Whitney is also testing higher thrust versions of the F135, partly in response to GE's claims that the F136 is capable of producing more thrust than the 43,000 lbf (190 kN) supplied by early F135s. The F135 has demonstrated a maximum thrust of over 50,000 lbf (220 kN) during testing.[98] The F-35's Pratt & Whitney F135 is the most powerful engine ever installed in a fighter aircraft.[99]

The F135 is the second (radar) stealthy afterburning jet engine and like the Pratt & Whitney F119 from which it was derived, has suffered from pressure pulsations in the afterburner at low altitude and high speed or "screech". In both cases this problem was fixed during development of the fighter program.[100]
Turbine bearing health in the engine will be monitored with thermoelectric powered wireless sensors.[101]

Armament

Close-up view of open aircraft weapons bay. The aircraft mock-up itself is on display, watched on by onlookers.
Weapons bay on a mock-up of the F-35

The F-35A includes a GAU-22/A, a four-barrel version of the GAU-12 Equalizer 25 mm cannon.[102] The cannon will be mounted internally with 180 rounds in the F-35A and fitted as an external pod with 220 rounds in the F-35B and F-35C.[103][104] The gun pod for the B and C variants will have stealth features. This pod could be used for different equipment in the future, such as EW, reconnaissance equipment, or possibly a rearward-facing radar.[105]

Internally, up to two 2,000 lb (910 kg) air-to-ground bombs can be carried in A and C models (BRU-68) (two 1,000 lb (450 kg) bombs in the B model (BRU-67)[106][107]) along with two smaller weapons, normally expected to be air-to-air missiles. Lockheed Martin says on its website that the weapons load can also be configured as all-air-to-ground or all-air-to-air, and has suggested that a Block 5 version will be able to carry three internal weapons per bay instead of two, replacing the heavy bomb with two smaller weapons such as AIM-120 AMRAAM air-to-air missiles.[108] 


Missiles and bombs to be carried inside the weapon bays include AIM-120 AMRAAM, AIM-132 ASRAAM, the Joint Direct Attack Munition (JDAM) – up to 2,000 lb (910 kg), the Joint Stand off Weapon (JSOW), Small Diameter Bombs (SDB) – a maximum of four in each bay (three per bay in F-35B,[109] or four GBU-53/B in each bay for all F-35 variants;[110] a set of up to four small diameter bombs takes the place of a single larger bomb), Brimstone anti-armor missiles, and Cluster Munitions (WCMD).[107] The MBDA Meteor air-to-air missile is currently being adapted to fit four internally in the missile spots and may be integrated into the F-35. A modified Meteor design with smaller tailfins for the F-35 was revealed in September 2010.[111] The United Kingdom had originally planned to put up to four AIM-132 ASRAAM internally but this has been changed to carry 2 internal and 2 external ASRAAMs.[112] The external ASRAAMs will add only an insignificant amount to the F-35's radar cross section and will allow attacks to slightly beyond visual range without using radar that might alert the target.[113]


At the expense of being more detectable by radar, many more missiles, bombs and fuel tanks can be attached on four wing pylons and two near wingtip positions. The two wingtip locations can only carry AIM-9X Sidewinder. The other pylons can carry the AIM-120 AMRAAM, Storm Shadow, AGM-158 Joint Air to Surface Stand-off Missile (JASSM) cruise missiles, guided bombs, 480 US gallons (1,800 L) and 600 US gallons (2,300 L) fuel tanks.[114] An air-to-air load of eight AIM-120s and two AIM-9s is conceivable using internal and external weapons stations, as well as a configuration of six 2,000 lb (910 kg) bombs, two AIM-120s and two AIM-9s.[107][115] With its payload capability, the F-35 can carry more weapons payload than the legacy fighters it is to replace as well as the F-22 Raptor.[116] Solid-state lasers were being developed as optional weapons for the F-35 as of 2002.[117][118][119]

While the F-35 will take on the Wild Weasel mission, it will lack the ability to carry an anti-radiation missile internally (and therefore stealthily) until the JDRADM is fielded in 2025.[120]

Norway and Australia are funding a program to adapt the Naval Strike Missile (NSM) to fit the internal bays of the F-35. This will be a multirole version, named the Joint Strike Missile (JSM), and will be the only cruise missile to fit the internal bays. Studies have shown that the F-35 would be able to carry two of these internally, while four additional missiles could be carried externally. The missile has an expected range in excess of 150 nmi (278 km).[121] On 12 April 2011 the Norwegian Ministry of Defence announced phase 2 of development with a cost estimate of 1029 MNOK.[122]

Tuesday, 7 June 2011

Apa Itu Relativitas Umum Einstein?

Banyak prediksi relativitas umum yang berbeda dengan prediksi fisika klasik, utamanya prediksi mengenai berjalannya waktu, geometri ruang, gerak benda pada jatuh bebas, dan perambatan cahaya.

Contoh perbedaan ini meliputi dilasi waktu gravitasional, geseran merah gravitasional cahaya, dan tunda waktu gravitasional. Prediksi-prediksi relativitas umum telah dikonfirmasikan dalam semua percobaan dan pengamatan fisika.

Walaupun relativitas umum bukanlah satu-satunya teori relativistik gravitasi, ia merupakan teori paling sederhana yang konsisten dengan data-data eksperimen. Namun, masih terdapat banyak pertanyaan yang belum terjawab.

Secara mendasar, terdapat pertanyaan bagaimanakah relativitas umum ini dapat digabungkan dengan hukum-hukum fisika kuantum untuk menciptakan teori gravitasi kuantum yang lengkap dan swa-konsisten.


Referensi:

Kunjungi Juga:

Memahami Relativitas Umum Einstein

Sumber: 

The University of Cambridge

Wikipedia

To Be Continued

Saturday, 4 June 2011

Mekanika Orbit: Hukum-Hukum Astro Dinamika

"Hukum-Hukum Astro Dinamika Akan Menjadi Dasar Bagi Pengembangan IPTEK Antariksa Masa Depan Umat Manusia" 
*Arip Nurahma*

The fundamental laws of astrodynamics are Newton's law of universal gravitation and Newton's laws of motion, while the fundamental mathematical tool is his differential calculus.
Standard assumptions in astrodynamics include non-interference from outside bodies, negligible mass for one of the bodies, and negligible other forces (such as from the solar wind, atmospheric drag, etc.). More accurate calculations can be made without these simplifying assumptions, but they are more complicated. The increased accuracy often does not make enough of a difference in the calculation to be worthwhile.
Kepler's laws of planetary motion may be derived from Newton's laws, when it is assumed that the orbiting body is subject only to the gravitational force of the central attractor. When an engine thrust or propulsive force is present, Newton's laws still apply, but Kepler's laws are invalidated. When the thrust stops, the resulting orbit will be different but will once again be described by Kepler's laws. The three laws are:
  1. The orbit of every planet is an ellipse with the sun at one of the foci.
  2. A line joining a planet and the sun sweeps out equal areas during equal intervals of time.
  3. The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axis of the orbits.

Escape velocity

The formula for escape velocity is easily derived as follows. The specific energy (energy per unit mass) of any space vehicle is composed of two components, the specific potential energy and the specific kinetic energy. The specific potential energy associated with a planet of mass M is given by

- G M / r \,
while the specific kinetic energy of an object is given by

v^2/2 \,

v^2/2 - G M / r \,
does not depend on the distance, r, from the center of the central body to the space vehicle in question. Therefore, the object can reach infinite r only if this quantity is nonnegative, which implies

v\geq\sqrt{2 G M / r}
The escape velocity from the Earth's surface is about 11 km/s, but that is insufficient to send the body an infinite distance because of the gravitational pull of the Sun. To escape the solar system from the vicinity of the Earth requires around 42 km/s velocity, but there will be "part credit" for the Earth's orbital velocity for spacecraft launched from Earth, if their further acceleration (due to the propulsion system) carries them in the same direction as Earth travels in its orbit.

Formulae for free orbits

Orbits are conic sections, so, naturally, the formula for the distance of a body for a given angle corresponds to the formula for that curve in polar coordinates, which is:
r = {a \over (1 + e \cos \theta) }.
The parameters are given by the orbital elements.

Circular orbits

Although most orbits are elliptical in nature, a special case is the circular orbit, which is an ellipse of zero eccentricity. The formula for the velocity of a body in a circular orbit at distance r from the center of gravity of mass M is
\ v = \sqrt{\frac{GM} {r}\
 }
where G is the gravitational constant, equal to
6.672 598 × 10−11 m3/(kg·s2)
To properly use this formula, the units must be consistent; for example, M must be in kilograms, and r must be in meters. The answer will be in meters per second.
The quantity GM is often termed the standard gravitational parameter, which has a different value for every planet or moon in the solar system.
Once the circular orbital velocity is known, the escape velocity is easily found by multiplying by the square root of 2:
\ v = 
\sqrt 2\sqrt{\frac {GM} {r}\ } = \sqrt{\frac {2GM} {r}\ }.
Sumber: Wikipedia