116-590: Orbital-1 , also known as Orb-1 , was the second flight of the Orbital Sciences Cygnus cargo spacecraft , its second flight to the International Space Station (ISS) and the third launch of the company's Antares launch vehicle . The mission launched on 9 January 2014 at 18:07:05 UTC . Orb-1 was the first of eight contracted flights by Orbital Sciences under NASA 's Commercial Resupply Services (CRS-1) contract. This
232-545: A 19-species model. An important aspect of modelling non-equilibrium real gas effects is radiative heat flux. If a vehicle is entering an atmosphere at very high speed (hyperbolic trajectory, lunar return) and has a large nose radius then radiative heat flux can dominate TPS heating. Radiative heat flux during entry into an air or carbon dioxide atmosphere typically comes from asymmetric diatomic molecules; e.g., cyanogen (CN), carbon monoxide , nitric oxide (NO), single ionized molecular nitrogen etc. These molecules are formed by
348-471: A Gibbs free energy equilibrium program, the iterative process from the originally specified molecular composition to the final calculated equilibrium composition is essentially random and not time accurate. With a non-equilibrium program, the computation process is time accurate and follows a solution path dictated by chemical and reaction rate formulas. The five species model has 17 chemical formulas (34 when counting reverse formulas). The Lighthill-Freeman model
464-499: A challenge. The experimental measurement of radiative heat flux (typically done with shock tubes) along with theoretical calculation through the unsteady Schrödinger equation are among the more esoteric aspects of aerospace engineering. Most of the aerospace research work related to understanding radiative heat flux was done in the 1960s, but largely discontinued after conclusion of the Apollo Program. Radiative heat flux in air
580-459: A complete sphere or a spherical section forebody with a converging conical afterbody. The aerodynamics of a sphere or spherical section are easy to model analytically using Newtonian impact theory. Likewise, the spherical section's heat flux can be accurately modeled with the Fay–Riddell equation . The static stability of a spherical section is assured if the vehicle's center of mass is upstream from
696-513: A considerable margin the constraints imposed on the mission to ensure the rocket's electronic systems are not impacted by a harsh radiation environment". Orbital later revised this, stating that a more extensive review of the radiation environment found it to be "within acceptable limits" of the Antares program, and that a launch would be attempted on 9 January 2014. The Orb-1 mission successfully launched on 9 January 2014 at 18:07:05 UTC from
812-564: A contract with Thales Alenia Space , Orbital is conducting integration and test services for Iridium NEXT , the next-generation satellite constellation of Iridium Communications Inc. Orbital will integrate the communications payloads and platforms for 81 low-Earth orbit Iridium NEXT satellites and test the systems at its satellite manufacturing facility in Gilbert, Arizona. Orbital Imaging spacecraft are designed to provide commercial Earth imaging services. The OrbView series of spacecraft paved
928-435: A converging conical afterbody. It flew a lifting entry with a hypersonic trim angle of attack of −27° (0° is blunt-end first) to yield an average L/D (lift-to-drag ratio) of 0.368. The resultant lift achieved a measure of cross-range control by offsetting the vehicle's center of mass from its axis of symmetry, allowing the lift force to be directed left or right by rolling the capsule on its longitudinal axis . Other examples of
1044-448: A definitive agreement with Alliant Techsystems to combine Orbital and ATK's Aerospace and Defense (A&D) Groups to create a US$ 4.5 billion (combined calendar year 2013 annual revenue), 13000-person company. The new company was called Orbital ATK, Inc . On 18 September 2017, Northrop Grumman announced plans to purchase Orbital ATK for US$ 7.8 billion in cash plus assumption of US$ 1.4 billion in debt. Orbital ATK shareholders approved
1160-455: A gas in equilibrium with fixed pressure and temperature can be determined through the Gibbs free energy method . Gibbs free energy is simply the total enthalpy of the gas minus its total entropy times temperature. A chemical equilibrium program normally does not require chemical formulas or reaction-rate equations. The program works by preserving the original elemental abundances specified for
1276-572: A gas that are important to aeronautical engineers who design heat shields: Almost all aeronautical engineers are taught the perfect (ideal) gas model during their undergraduate education. Most of the important perfect gas equations along with their corresponding tables and graphs are shown in NACA Report 1135. Excerpts from NACA Report 1135 often appear in the appendices of thermodynamics textbooks and are familiar to most aeronautical engineers who design supersonic aircraft. The perfect gas theory
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#17327824283751392-574: A heat shield designer must use a real gas model . An entry vehicle's pitching moment can be significantly influenced by real-gas effects. Both the Apollo command module and the Space Shuttle were designed using incorrect pitching moments determined through inaccurate real-gas modelling. The Apollo-CM's trim-angle angle of attack was higher than originally estimated, resulting in a narrower lunar return entry corridor. The actual aerodynamic center of
1508-534: A leading supplier of 1.5 - 5.5 kilowatt Geosynchronous-Earth Orbit (GEO) communications satellites used to provide direct-to-home TV broadcasting, cable program distribution, business data network capacity, regional mobile communications and similar services. With its new GEOStar-3 satellite platform, Orbital is extending its capabilities with up to 8 kW of total satellite payload power. The list of Orbital built GeoStar satellites are provided next. LEO communications satellites Orbital
1624-656: A mock-up of the ablative material to be analyzed within a hypersonic wind tunnel. Testing of ablative materials occurs at the Ames Arc Jet Complex. Many spacecraft thermal protection systems have been tested in this facility, including the Apollo, space shuttle, and Orion heat shield materials. Carbon phenolic was originally developed as a rocket nozzle throat material (used in the Space Shuttle Solid Rocket Booster ) and for reentry-vehicle nose tips. The thermal conductivity of
1740-430: A new company called Orbital ATK. The merger was completed on 9 February 2015 and Orbital Sciences ceased to exist as an independent entity. On 18 September 2017, Northrop Grumman announced plans to purchase Orbital ATK for US$ 7.8 billion in cash plus assumption of US$ 1.4 billion in debt, and on 6 June 2018, the acquisition was completed, and Orbital ATK became Northrop Grumman Innovation Systems. As of 1 January 2020,
1856-555: A new facility in Chandler, Arizona in 1989 to house the company's expanding rocket business. In 1990, the company successfully carried out eight space missions, highlighted by the initial launch of the Pegasus launch vehicle, the world's first privately developed space launch vehicle (the claim of being the first privately developed space launch vehicle can be contested as Pegasus received significant funding from NASA and DARPA , and
1972-454: A nose radius of 1 meter, i.e., time of travel is about 18 microseconds. This is roughly the time required for shock-wave-initiated chemical dissociation to approach chemical equilibrium in a shock layer for a 7.8 km/s entry into air during peak heat flux. Consequently, as air approaches the entry vehicle's stagnation point, the air effectively reaches chemical equilibrium thus enabling an equilibrium model to be usable. For this case, most of
2088-402: A nose radius of 2.34 cm, a forward-frustum half-angle of 10.4°, an inter-frustum radius of 14.6 cm, aft-frustum half-angle of 6°, and an axial length of 2.079 meters. No accurate diagram or picture of AMaRV has ever appeared in the open literature. However, a schematic sketch of an AMaRV-like vehicle along with trajectory plots showing hairpin turns has been published. AMaRV's attitude
2204-461: A particular TPS material is usually proportional to the material's density. Carbon phenolic is a very effective ablative material, but also has high density which is undesirable. The NASA Galileo Probe used carbon phenolic for its TPS material. If the heat flux experienced by an entry vehicle is insufficient to cause pyrolysis then the TPS material's conductivity could allow heat flux conduction into
2320-421: A perfect gas model, the ratio of specific heats (also called isentropic exponent , adiabatic index , gamma , or kappa ) is assumed to be constant along with the gas constant . For a real gas, the ratio of specific heats can wildly oscillate as a function of temperature. Under a perfect gas model there is an elegant set of equations for determining thermodynamic state along a constant entropy stream line called
2436-630: A predecessor private rocket exists, the Conestoga rocket). Shortly following the successful Pegasus launch, Orbital conducted an initial public offering (IPO) in 1990 and began trading on the NASDAQ stock exchange. In 1993, Orbital established its headquarters in Dulles, Virginia . In 1994, Orbital successfully conducted the inaugural launch of the Taurus (now renamed as Minotaur-C ) launch vehicle. In
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#17327824283752552-603: A series of delays pushed the date to 20 December 2013. The Antares launch vehicle rolled out from the Wallops Horizontal Integration Facility (HIF) on the morning of 17 December 2013, and was later erected at Launch Pad 0A. Later that day, due to the need for a series of spacewalks to fix a faulty coolant system on the International Space Station, NASA directed Orbital Sciences to stand down the Antares rocket. Antares
2668-428: A specific destination on the surface at zero velocity while keeping stresses on the spacecraft and any passengers within acceptable limits. This may be accomplished by propulsive or aerodynamic (vehicle characteristics or parachute ) means, or by some combination. There are several basic shapes used in designing entry vehicles: The simplest axisymmetric shape is the sphere or spherical section. This can either be
2784-407: A sphere-cone shape and were the first American example of a non-munition entry vehicle ( Discoverer-I , launched on 28 February 1959). The sphere-cone was later used for space exploration missions to other celestial bodies or for return from open space; e.g., Stardust probe. Unlike with military RVs, the advantage of the blunt body's lower TPS mass remained with space exploration entry vehicles like
2900-521: A stream of vaporized metal making it very visible to radar . These defects made the Mk-2 overly susceptible to anti-ballistic missile (ABM) systems. Consequently, an alternative sphere-cone RV to the Mk-2 was developed by General Electric. This new RV was the Mk-6 which used a non-metallic ablative TPS, a nylon phenolic. This new TPS was so effective as a reentry heat shield that significantly reduced bluntness
3016-411: A trailing vortex behind the entry vehicle. Correctly modelling the flow in the wake of an entry vehicle is very difficult. Thermal protection shield (TPS) heating in the vehicle's afterbody is usually not very high, but the geometry and unsteadiness of the vehicle's wake can significantly influence aerodynamics (pitching moment) and particularly dynamic stability. A thermal protection system , or TPS,
3132-478: Is also a provider of low-Earth orbit (LEO) communications satellites, having conceived, built and deployed the ORBCOMM network. ORBCOMM was the first global communications network to employ a constellation of LEO satellites. From 1994–1999, Orbital built and deployed 35 satellites, and integrated five “gateway” ground stations and a network operations center to manage the satellites and process their data. Under
3248-531: Is another entry vehicle geometry and was used with the X-23 PRIME (Precision Recovery Including Maneuvering Entry) vehicle. Objects entering an atmosphere from space at high velocities relative to the atmosphere will cause very high levels of heating . Atmospheric entry heating comes principally from two sources: As velocity increases, both convective and radiative heating increase, but at different rates. At very high speeds, radiative heating will dominate
3364-465: Is at 400,000 feet (122 km), the main heating during controlled entry takes place at altitudes of 65 to 35 kilometres (213,000 to 115,000 ft), peaking at 58 kilometres (190,000 ft). At typical reentry temperatures, the air in the shock layer is both ionized and dissociated . This chemical dissociation necessitates various physical models to describe the shock layer's thermal and chemical properties. There are four basic physical models of
3480-506: Is based upon a single ordinary differential equation and one algebraic equation. The five species model is based upon 5 ordinary differential equations and 17 algebraic equations. Because the 5 ordinary differential equations are tightly coupled, the system is numerically "stiff" and difficult to solve. The five species model is only usable for entry from low Earth orbit where entry velocity is approximately 7.8 km/s (28,000 km/h; 17,000 mph). For lunar return entry of 11 km/s,
3596-622: Is capable of delivering 2,000 kg of pressurized cargo to the ISS. An enhanced version to be flown in later CRS missions is able to deliver 2,700 kg of pressurized cargo. The first of the eight contracted Cygnus missions to the ISS was completed on 18 February 2014. The October 28, 2014, launch failure was the third contracted Cygnus mission to the ISS. Orbital's Missile Defense Systems product line consists of interceptors and target vehicles. GEO communications satellites With its proprietary GEOStar-2 satellite platform, Orbital has become
Cygnus Orb-1 - Misplaced Pages Continue
3712-642: Is currently scheduled for 2017. Orbital's heritage programs in advanced flight systems include the NASA X-34 and X-43 programs, and the Orion Launch Abort System , among others. Atmospheric entry Atmospheric entry (sometimes listed as V impact or V entry ) is the movement of an object from outer space into and through the gases of an atmosphere of a planet , dwarf planet , or natural satellite . There are two main types of atmospheric entry: uncontrolled entry , such as
3828-448: Is elegant and extremely useful for designing aircraft but assumes that the gas is chemically inert. From the standpoint of aircraft design, air can be assumed to be inert for temperatures less than 550 K (277 °C; 530 °F) at one atmosphere pressure. The perfect gas theory begins to break down at 550 K and is not usable at temperatures greater than 2,000 K (1,730 °C; 3,140 °F). For temperatures greater than 2,000 K,
3944-466: Is lower than other high-heat-flux-ablative materials, such as conventional carbon phenolics. PICA was patented by NASA Ames Research Center in the 1990s and was the primary TPS material for the Stardust aeroshell. The Stardust sample-return capsule was the fastest man-made object ever to reenter Earth's atmosphere, at 28,000 mph (ca. 12.5 km/s) at 135 km altitude. This was faster than
4060-666: Is one of two companies providing commercial cargo resupply services to the ISS for NASA. Orbital's medium-class rocket - Antares is used to launch the Cygnus advanced maneuvering spacecraft to deliver cargo to the ISS. Under the Commercial Resupply Services (CRS) contract with NASA, Orbital will perform eight cargo missions to the ISS. Operational flights began in 2013 from the new Mid-Atlantic Regional Spaceport (MARS) at Wallops Island in Virginia. In addition,
4176-528: Is pre-bonded to the aeroshell's structure thus enabling construction of a large heat shield. Phenolic-impregnated carbon ablator (PICA), a carbon fiber preform impregnated in phenolic resin , is a modern TPS material and has the advantages of low density (much lighter than carbon phenolic) coupled with efficient ablative ability at high heat flux. It is a good choice for ablative applications such as high-peak-heating conditions found on sample-return missions or lunar-return missions. PICA's thermal conductivity
4292-446: Is slowly reduced such that chemical reactions can continue then the gas can remain in equilibrium. However, it is possible for gas pressure to be so suddenly reduced that almost all chemical reactions stop. For that situation the gas is considered frozen. The distinction between equilibrium and frozen is important because it is possible for a gas such as air to have significantly different properties (speed-of-sound, viscosity etc.) for
4408-457: Is the barrier that protects a spacecraft during the searing heat of atmospheric reentry. Multiple approaches for the thermal protection of spacecraft are in use, among them ablative heat shields, passive cooling, and active cooling of spacecraft surfaces. In general they can be divided into two categories: ablative TPS and reusable TPS. Ablative TPS are required when space craft reach a relatively low altitude before slowing down. Spacecraft like
4524-412: Is the only way of expending this, as it is highly impractical to use retrorockets for the entire reentry procedure. Ballistic warheads and expendable vehicles do not require slowing at reentry, and in fact, are made streamlined so as to maintain their speed. Furthermore, slow-speed returns to Earth from near-space such as high-altitude parachute jumps from balloons do not require heat shielding because
4640-453: Is typically better than that of a spherical section. The vehicle enters sphere-first. With a sufficiently small half-angle and properly placed center of mass, a sphere-cone can provide aerodynamic stability from Keplerian entry to surface impact. (The half-angle is the angle between the cone's axis of rotational symmetry and its outer surface, and thus half the angle made by the cone's surface edges.) The original American sphere-cone aeroshell
4756-490: The Columbia was upstream from the calculated value due to real-gas effects. On Columbia ' s maiden flight ( STS-1 ), astronauts John Young and Robert Crippen had some anxious moments during reentry when there was concern about losing control of the vehicle. An equilibrium real-gas model assumes that a gas is chemically reactive, but also assumes all chemical reactions have had time to complete and all components of
Cygnus Orb-1 - Misplaced Pages Continue
4872-501: The Eastern United States , including maps indicating launch vehicle maximum elevation above horizon and time of first sighting after launch for the various viewing locations. Cygnus was filled with 1,260 kg (2,780 lb) of supplies for the ISS, including science experiments and hardware to expand the research capability of the station, crew provisions and spare parts. This included 12 experiments flying as part of
4988-642: The G77 Fortran compiler. A non-equilibrium real gas model is the most accurate model of a shock layer's gas physics, but is more difficult to solve than an equilibrium model. The simplest non-equilibrium model is the Lighthill-Freeman model developed in 1958. The Lighthill-Freeman model initially assumes a gas made up of a single diatomic species susceptible to only one chemical formula and its reverse; e.g., N 2 = N + N and N + N = N 2 (dissociation and recombination). Because of its simplicity,
5104-592: The Galileo Probe with a half-angle of 45° or the Viking aeroshell with a half-angle of 70°. Space exploration sphere-cone entry vehicles have landed on the surface or entered the atmospheres of Mars , Venus , Jupiter , and Titan . The biconic is a sphere-cone with an additional frustum attached. The biconic offers a significantly improved L/D ratio. A biconic designed for Mars aerocapture typically has an L/D of approximately 1.0 compared to an L/D of 0.368 for
5220-673: The Harmony module on 18 February 2014 at 10:25 UTC. The spacecraft was then maneuvered to a position below the station, where it was released from the Canadarm2 at 11:41 UTC. It then performed a series of separation maneuvers to move it away from the station. The spacecraft reentered the atmosphere and burned up on 19 February 2014 over the southern Pacific Ocean , disposing of approximately 1,470 kg (3,240 lb) of trash. Orbital Sciences Corporation Orbital Sciences Corporation (commonly referred to as Orbital )
5336-583: The Hosted Infrared Payload (CHIRP) program for the U.S. Air Force . The wide-field of view sensor was hosted on an Orbital-built commercial GEO communications satellite. Orbital's hosted payload program takes advantage of the high frequency of commercial satellite launches and the excess resources that typically exist on a commercial communications satellite to provide frequent and low-cost access to space for National Security Systems. Orbital's current advanced flight systems programs include
5452-592: The National Radio Astronomy Observatory (NRAO). The TMS unit combined satellite navigation and wireless communications to enable transit control centers to manage the dispatch of public transit, highway service vehicles and commuter light rail systems. As of 2008, the technology was used by more than 60 clients, exceeding 27500 vehicles, or more than 30% of the United States and Canada fleet. TMS clients included some of
5568-815: The New York Stock Exchange with the ticker symbol ORB . Orbital's primary products were satellites and launch vehicles , including low Earth orbit (LEO), geosynchronous Earth orbit and planetary spacecraft for communications , remote sensing , scientific and defense missions; ground- and air-launched launch vehicles that delivered satellites into orbit; missile defense systems that were used as interceptor and target vehicles; and human-rated space systems for Earth orbit, lunar and other missions. Orbital also provided satellite subsystems and space-related technical services to government agencies and laboratories. On 29 April 2014, Orbital Sciences announced that it would merge with Alliant Techsystems to create
5684-480: The Soyuz ), or unbounded (e.g., meteors ) trajectories. Various advanced technologies have been developed to enable atmospheric reentry and flight at extreme velocities. An alternative method of controlled atmospheric entry is buoyancy which is suitable for planetary entry where thick atmospheres, strong gravity, or both factors complicate high-velocity hyperbolic entry, such as the atmospheres of Venus , Titan and
5800-556: The Student Spaceflight Experiments Program (SSEP), selected from 1,466 entrants and involving 7,200 North American students . Types of cargo include: Some of the major experiments focus on: Cygnus also contained 33 cubesat , making the total number of spacecraft aboard the Antares up to 34, including the Cygnus itself. [1] Canadarm2 unberthed the Cygnus spacecraft from the nadir port of
5916-611: The V-2 , stabilization and aerodynamic stress were important issues (many V-2s broke apart during reentry), but heating was not a serious problem. Medium-range missiles like the Soviet R-5 , with a 1,200-kilometer (650-nautical-mile) range, required ceramic composite heat shielding on separable reentry vehicles (it was no longer possible for the entire rocket structure to survive reentry). The first ICBMs , with ranges of 8,000 to 12,000 km (4,300 to 6,500 nmi), were only possible with
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#17327824283756032-408: The giant planets . The concept of the ablative heat shield was described as early as 1920 by Robert Goddard : "In the case of meteors, which enter the atmosphere with speeds as high as 30 miles (48 km) per second, the interior of the meteors remains cold, and the erosion is due, to a large extent, to chipping or cracking of the suddenly heated surface. For this reason, if the outer surface of
6148-419: The isentropic chain . For a real gas, the isentropic chain is unusable and a Mollier diagram would be used instead for manual calculation. However, graphical solution with a Mollier diagram is now considered obsolete with modern heat shield designers using computer programs based upon a digital lookup table (another form of Mollier diagram) or a chemistry based thermodynamics program. The chemical composition of
6264-640: The 35-satellite ORBCOMM data communications network, and the 81 spacecraft (integration and test) for the IridiumNEXT constellation. Earth imagery and high resolution digital imaging satellites such as the OrbView series are also developed and manufactured by Orbital. The science and environmental satellites developed by Orbital perform scientific research, carry out deep space exploration (e.g. Dawn spacecraft), conduct remote sensing missions (e.g. Landsat 4, 5 and 8 ), and demonstrate new space technologies. In
6380-548: The 70° sphere-cone entry vehicles sent by NASA to Mars other than the Mars Science Laboratory (MSL). SLA-561V begins significant ablation at a heat flux of approximately 110 W/cm , but will fail for heat fluxes greater than 300 W/cm . The MSL aeroshell TPS is currently designed to withstand a peak heat flux of 234 W/cm . The peak heat flux experienced by the Viking 1 aeroshell which landed on Mars
6496-634: The Apollo mission capsules and 70% faster than the Shuttle. PICA was critical for the viability of the Stardust mission, which returned to Earth in 2006. Stardust's heat shield (0.81 m base diameter) was made of one monolithic piece sized to withstand a nominal peak heating rate of 1.2 kW/cm . A PICA heat shield was also used for the Mars Science Laboratory entry into the Martian atmosphere . An improved and easier to produce version called PICA-X
6612-787: The Apollo-CM. The higher L/D makes a biconic shape better suited for transporting people to Mars due to the lower peak deceleration. Arguably, the most significant biconic ever flown was the Advanced Maneuverable Reentry Vehicle (AMaRV). Four AMaRVs were made by the McDonnell Douglas Corp. and represented a significant leap in RV sophistication. Three AMaRVs were launched by Minuteman-1 ICBMs on 20 December 1979, 8 October 1980 and 4 October 1981. AMaRV had an entry mass of approximately 470 kg,
6728-676: The DC-X also served as the basis for an unsuccessful proposal for what eventually became the Lockheed Martin X-33 . Non- axisymmetric shapes have been used for crewed entry vehicles. One example is the winged orbit vehicle that uses a delta wing for maneuvering during descent much like a conventional glider. This approach has been used by the American Space Shuttle and the Soviet Buran . The lifting body
6844-504: The Earth under the influence of Earth's gravity , and are slowed by friction upon encountering Earth's atmosphere. Meteors are also often travelling quite fast relative to the Earth simply because their own orbital path is different from that of the Earth before they encounter Earth's gravity well . Most objects enter at hypersonic speeds due to their sub-orbital (e.g., intercontinental ballistic missile reentry vehicles), orbital (e.g.,
6960-533: The Lighthill-Freeman model is a useful pedagogical tool, but is too simple for modelling non-equilibrium air. Air is typically assumed to have a mole fraction composition of 0.7812 molecular nitrogen, 0.2095 molecular oxygen and 0.0093 argon. The simplest real gas model for air is the five species model , which is based upon N 2 , O 2 , NO, N, and O. The five species model assumes no ionization and ignores trace species like carbon dioxide. When running
7076-534: The Mid-Atlantic Regional Spaceport Launch Pad 0A. Solar array deployment occurred shortly after arriving in orbit. The Cygnus spacecraft arrived at the International Space Station early on 12 January 2014. The launch was expected to be viewable from South Carolina through Massachusetts and as far west as West Virginia . As with its last couple of launches out of Wallops, Orbital Sciences released viewing information for
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#17327824283757192-488: The TPS bondline material thus leading to TPS failure. Consequently, for entry trajectories causing lower heat flux, carbon phenolic is sometimes inappropriate and lower-density TPS materials such as the following examples can be better design choices: SLA in SLA-561V stands for super light-weight ablator . SLA-561V is a proprietary ablative made by Lockheed Martin that has been used as the primary TPS material on all of
7308-535: The U.S. missile defense systems. In the last 10 years, Orbital conducted nearly 50 major launches for the U.S. Missile Defense Agency (MDA), the U.S. Air Force , the U.S. Army and U.S. Navy to develop, test and enhance U.S. missile defense systems. Orbital's Advanced Programs Group focused on developing and producing human-rated space systems, satellites and related systems for national security space programs, and advanced flight systems for atmospheric and space missions. In support of human space systems, Orbital
7424-442: The apparatus were to consist of layers of a very infusible hard substance with layers of a poor heat conductor between, the surface would not be eroded to any considerable extent, especially as the velocity of the apparatus would not be nearly so great as that of the average meteor." Practical development of reentry systems began as the range, and reentry velocity of ballistic missiles increased. For early short-range missiles, like
7540-410: The areas that its customers are pursuing. The Orbital employees often work side-by-side with the customers' technical staff at their facilities. They perform a wide range of functions, from system-level efforts such as special payload equipment and training support for NASA's Hubble Space Telescope servicing missions to component-level tasks including development of high-energy microwave transmitters for
7656-422: The atmospheric entry returns to the same body that the vehicle had launched from, the event is referred to as reentry (almost always referring to Earth entry). The fundamental design objective in atmospheric entry of a spacecraft is to dissipate the energy of a spacecraft that is traveling at hypersonic speed as it enters an atmosphere such that equipment, cargo, and any passengers are slowed and land near
7772-929: The buyout on 29 November 2017. The Federal Trade Commission (FTC) approved the acquisition with conditions on 5 June 2018, and one day later, Orbital ATK were absorbed and became Northrop Grumman Innovation Systems . Orbital was a provider of small- to medium-class satellites. Since the company's founding in 1982, Orbital has delivered 150 spacecraft to commercial, military and civil customers worldwide. To date, these spacecraft have amassed well over 1000 years of on-orbit operations. The communications and imaging satellites developed by Orbital are smaller and more affordable. The geosynchronous orbit (GEO) communications satellites provide commercial satellite services such as direct-to-home digital television , business data transmission, cable program distribution and wireless communications. In addition, Orbital also provides constellations of low Earth orbit communications satellites such as
7888-469: The case of the Galileo probe's entry into Jupiter's atmosphere, the shock layer was mostly in equilibrium during peak heat flux due to the very high pressures experienced (this is counterintuitive given the free stream velocity was 39 km/s during peak heat flux). Determining the thermodynamic state of the stagnation point is more difficult under an equilibrium gas model than a perfect gas model. Under
8004-402: The center of curvature (dynamic stability is more problematic). Pure spheres have no lift. However, by flying at an angle of attack , a spherical section has modest aerodynamic lift thus providing some cross-range capability and widening its entry corridor. In the late 1950s and early 1960s, high-speed computers were not yet available and computational fluid dynamics was still embryonic. Because
8120-444: The company is exploring opportunities to adapt the Cygnus design for other possible space exploration applications. For National Security Space systems, Orbital provides products ranging from smaller, more affordable spacecraft busses to hosted payload applications. For Advanced Flight systems, Orbital is applying its to design and build an intermediate-class air-launched rocket system for Stratolaunch Systems . Orbital has developed
8236-429: The contract with Stratolaunch Systems to design a new intermediate-class rocket to be carried aloft and launched from the largest aircraft ever built- Stratolaunch carrier aircraft . Orbital is responsible for the program's overall systems engineering, and the development, production, test, and operations of the air-launch rocket and related ground operations, including payload and launch vehicle integration. A demo launch
8352-418: The convective heat fluxes, as radiative heating is proportional to the eighth power of velocity, while convective heating is proportional to the third power of velocity. Radiative heating thus predominates early in atmospheric entry, while convection predominates in the later phases. During certain intensity of ionization, a radio-blackout with the spacecraft is produced. While NASA's Earth entry interface
8468-457: The cost and accelerate the development and deployment of national security space systems. For example, Orbital's GEOStar-1 spacecraft provides a compact platform optimized for GEO missions (adaptable for MEO for launch aboard Minotaur , Falcon , and EELV launch vehicles to deliver resilient capabilities in a relatively short period of time (years instead of decades). Orbital's hosted payload capabilities in national security systems include
8584-587: The development of modern ablative heat shields and blunt-shaped vehicles. In the United States, this technology was pioneered by H. Julian Allen and A. J. Eggers Jr. of the National Advisory Committee for Aeronautics (NACA) at Ames Research Center . In 1951, they made the counterintuitive discovery that a blunt shape (high drag) made the most effective heat shield. From simple engineering principles, Allen and Eggers showed that
8700-468: The development of the Antares space launch vehicle, Orbital is extending its capabilities to provide medium-class launch services for U.S. government , commercial and international customers. The inaugural launch of Antares occurred on 21 April 2013 from Wallops Flight Facility (WFF) at Wallops Island , Virginia. Orbital is also a major provider of suborbital target and interceptor launch vehicles for
8816-404: The early 2000s, Orbital continued expanding its missile defense systems business with a US$ 900 million award to develop, build, test and support interceptor booster vehicles. In 2006, Orbital conducted its 500th mission since the company's founding with products that included satellites, launch vehicles, and missile defense systems. In 2007, the first interplanetary spacecraft built by Orbital, Dawn
8932-422: The entry of astronomical objects , space debris , or bolides ; and controlled entry (or reentry ) of a spacecraft capable of being navigated or following a predetermined course. Technologies and procedures allowing the controlled atmospheric entry, descent, and landing of spacecraft are collectively termed as EDL . Objects entering an atmosphere experience atmospheric drag , which puts mechanical stress on
9048-529: The fast-growing Geosynchronous (GEO) communications satellite market. In 2010, Orbital acquired the Gilbert, Arizona -based satellite development and manufacturing unit from General Dynamics (General Dynamics Advanced Information Systems, formerly Spectrum Astro) to complement its main satellite manufacturing facility in Dulles, Virginia. On 29 April 2014, Orbital Sciences announced that it had entered into
9164-447: The gas and varying the different molecular combinations of the elements through numerical iteration until the lowest possible Gibbs free energy is calculated (a Newton–Raphson method is the usual numerical scheme). The data base for a Gibbs free energy program comes from spectroscopic data used in defining partition functions . Among the best equilibrium codes in existence is the program Chemical Equilibrium with Applications (CEA) which
9280-432: The gas have the same temperature (this is called thermodynamic equilibrium ). When air is processed by a shock wave, it is superheated by compression and chemically dissociates through many different reactions. Direct friction upon the reentry object is not the main cause of shock-layer heating. It is caused mainly from isentropic heating of the air molecules within the compression wave. Friction based entropy increases of
9396-648: The gravitational acceleration of an object starting at relative rest from within the atmosphere itself (or not far above it) cannot create enough velocity to cause significant atmospheric heating. For Earth, atmospheric entry occurs by convention at the Kármán line at an altitude of 100 km (62 miles; 54 nautical miles) above the surface, while at Venus atmospheric entry occurs at 250 km (160 mi; 130 nmi) and at Mars atmospheric entry at about 80 km (50 mi; 43 nmi). Uncontrolled objects reach high velocities while accelerating through space toward
9512-408: The heat load experienced by an entry vehicle was inversely proportional to the drag coefficient ; i.e., the greater the drag, the less the heat load. If the reentry vehicle is made blunt, air cannot "get out of the way" quickly enough, and acts as an air cushion to push the shock wave and heated shock layer forward (away from the vehicle). Since most of the hot gases are no longer in direct contact with
9628-444: The hot shock layer gas away from the heat shield's outer wall (creating a cooler boundary layer ). The boundary layer comes from blowing of gaseous reaction products from the heat shield material and provides protection against all forms of heat flux. The overall process of reducing the heat flux experienced by the heat shield's outer wall by way of a boundary layer is called blockage . Ablation occurs at two levels in an ablative TPS:
9744-872: The last 10 years, Orbital has built more scientific and environmental monitoring satellites for NASA than any other company. Orbital's space launch vehicles are considered the industry standard for boosting small payloads to orbit. The Pegasus launch vehicle is launched from the company's L-1011 carrier aircraft, Stargazer and has proven to be the industry's small space launch workhorse, having conducted 40 missions from six different launch sites worldwide since 1990. The Minotaur ground-launched launch vehicles combine Pegasus upper-stages with either government-supplied or commercially available first-stage rocket motors to boost larger payloads to orbit. Minotaur IV combines decommissioned Peacekeeper rocket motors with proven Orbital avionics and fairings to provide increased lifting capacity for government-sponsored payloads. With
9860-727: The mission requirements and budget. Astrophysics satellites Orbital's current and heritage astrophysics satellites are as listed below: Remote sensing/Earth observation Orbital's current and heritage Remote Sensing/Earth Observation satellites are as listed below: Heliophysics Orbital's heritage Heliophysics satellites are as listed below: Planetary exploration Orbital's heritage Planetary Exploration Heliophysics satellites are as listed below: Orbital's national security systems range from smaller, more affordable spacecraft buses (e.g. disaggregated systems) to hosted payload applications. Orbital advocates disaggregated systems because conceptually disaggregated systems can lower
9976-438: The molecules within the wave also account for some heating. The distance from the shock wave to the stagnation point on the entry vehicle's leading edge is called shock wave stand off . An approximate rule of thumb for shock wave standoff distance is 0.14 times the nose radius. One can estimate the time of travel for a gas molecule from the shock wave to the stagnation point by assuming a free stream velocity of 7.8 km/s and
10092-603: The name was changed to Space Systems under a large restructuring and rebranding initiative. Orbital was founded and incorporated in 1982 by three friends who had met earlier while at Harvard Business School — David W. Thompson, Bruce Walker Ferguson , and Scott L. Webster. Initial capitalization for Orbital was provided by Fred C. Alcorn, a Texas oilman and Sam Dunnam, a Texas businessman in September 1982. In 1985, Orbital procured its first contract for providing up to four transfer orbital stage (TOS) vehicles to NASA . In 1987,
10208-568: The nation's largest fleet management systems, such as Los Angeles , Chicago , and Washington, D.C. In 2008, the technology services provider Affiliated Computer Services (ACS) Inc. agreed to buy the Transportation Management Systems unit for US$ 42.5 million. The sale transferred an estimated 130 to 140 Orbital employees based in Columbia, Maryland , to ACS. Orbital's primary locations are listed below- With
10324-595: The object, and aerodynamic heating —caused mostly by compression of the air in front of the object, but also by drag. These forces can cause loss of mass ( ablation ) or even complete disintegration of smaller objects, and objects with lower compressive strength can explode. Reentry has been achieved with speeds ranging from 7.8 km/s for low Earth orbit to around 12.5 km/s for the Stardust probe. Crewed space vehicles must be slowed to subsonic speeds before parachutes or air brakes may be deployed. Such vehicles have high kinetic energies, and atmospheric dissipation
10440-517: The operational concept and completed the preliminary design for the air-launched rocket. It will be responsible for the development, production, test and operations of the full system and related ground operations. The Technical Services Division (TSD) provided engineering, production and technical management expertise primarily for space-related science and defense programs. Typically, it supplies specialized personnel — engineers, scientists, technicians and other professionals — with specific knowledge in
10556-481: The outer surface of the TPS material chars, melts, and sublimes , while the bulk of the TPS material undergoes pyrolysis and expels product gases. The gas produced by pyrolysis is what drives blowing and causes blockage of convective and catalytic heat flux. Pyrolysis can be measured in real time using thermogravimetric analysis , so that the ablative performance can be evaluated. Ablation can also provide blockage against radiative heat flux by introducing carbon into
10672-451: The same thermodynamic state; e.g., pressure and temperature. Frozen gas can be a significant issue in the wake behind an entry vehicle. During reentry, free stream air is compressed to high temperature and pressure by the entry vehicle's shock wave. Non-equilibrium air in the shock layer is then transported past the entry vehicle's leading side into a region of rapidly expanding flow that causes freezing. The frozen air can then be entrained into
10788-513: The seeds for the Orbcomm constellation were planted when Orbital began investigating a system using low Earth orbit (LEO) satellites to collect data from remote locations. In 1988, Orbital acquired Space Data Corporation in Arizona — one of the world's leading suppliers of suborbital rockets — thereby broadening its rocket business and manufacturing capabilities. This was followed by the opening of
10904-430: The shock layer between the shock wave and leading edge of an entry vehicle is chemically reacting and not in a state of equilibrium. The Fay–Riddell equation , which is of extreme importance towards modeling heat flux, owes its validity to the stagnation point being in chemical equilibrium. The time required for the shock layer gas to reach equilibrium is strongly dependent upon the shock layer's pressure. For example, in
11020-447: The shock layer contains a significant amount of ionized nitrogen and oxygen. The five-species model is no longer accurate and a twelve-species model must be used instead. Atmospheric entry interface velocities on a Mars–Earth trajectory are on the order of 12 km/s (43,000 km/h; 27,000 mph). Modeling high-speed Mars atmospheric entry—which involves a carbon dioxide, nitrogen and argon atmosphere—is even more complex requiring
11136-589: The shock layer thus making it optically opaque. Radiative heat flux blockage was the primary thermal protection mechanism of the Galileo Probe TPS material (carbon phenolic). Early research on ablation technology in the USA was centered at NASA 's Ames Research Center located at Moffett Field , California. Ames Research Center was ideal, since it had numerous wind tunnels capable of generating varying wind velocities. Initial experiments typically mounted
11252-399: The shock wave dissociating ambient atmospheric gas followed by recombination within the shock layer into new molecular species. The newly formed diatomic molecules initially have a very high vibrational temperature that efficiently transforms the vibrational energy into radiant energy ; i.e., radiative heat flux. The whole process takes place in less than a millisecond which makes modelling
11368-408: The space shuttle are designed to slow down at high altitude so that they can use reuseable TPS. (see: Space Shuttle thermal protection system ). Thermal protection systems are tested in high enthalpy ground testing or plasma wind tunnels that reproduce the combination of high enthalpy and high stagnation pressure using Induction plasma or DC plasma. The ablative heat shield functions by lifting
11484-471: The spherical section geometry in crewed capsules are Soyuz / Zond , Gemini , and Mercury . Even these small amounts of lift allow trajectories that have very significant effects on peak g-force , reducing it from 8–9 g for a purely ballistic (slowed only by drag) trajectory to 4–5 g, as well as greatly reducing the peak reentry heat. The sphere-cone is a spherical section with a frustum or blunted cone attached. The sphere-cone's dynamic stability
11600-483: The spherical section was amenable to closed-form analysis, that geometry became the default for conservative design. Consequently, crewed capsules of that era were based upon the spherical section. Pure spherical entry vehicles were used in the early Soviet Vostok and Voskhod capsules and in Soviet Mars and Venera descent vehicles. The Apollo command module used a spherical section forebody heat shield with
11716-505: The success of Cygnus Orb-D1 and Cygnus CRS Orb-1 . Orbital Science made a number of strategic acquisitions in the 1990s and 2000s to strengthen its position in the satellite market. In 1994, Orbital completed acquisition of Fairchild Industries ' subsidiary Space and Defense Corporation, and merged the Fairchild Space business with its own satellite design and manufacturing division. The electronics business of this subsidiary
11832-504: The successful demonstration in September 2013 of the Cygnus spacecraft and the Antares launch vehicle under the Commercial Orbital Transportation Services (COTS) program, Orbital commenced regular ISS cargo missions under the Commercial Resupply Services (CRS) contract. The total NASA contract to Orbital is worth $ 1.9 Billion for providing eight pressurized cargo missions to the ISS. Cygnus
11948-455: The vehicle, the heat energy would stay in the shocked gas and simply move around the vehicle to later dissipate into the atmosphere. The Allen and Eggers discovery, though initially treated as a military secret, was eventually published in 1958. When atmospheric entry is part of a spacecraft landing or recovery, particularly on a planetary body other than Earth, entry is part of a phase referred to as entry, descent, and landing , or EDL. When
12064-773: The way for today's space-based Earth imaging industry. In addition to the OrbView satellites the company also built the GeoEye-1 high resolution imaging satellite. Orbital LEOStar-2 and -3 spacecraft platforms are designed to support a variety of multispectral, visible and thermal imaging payloads. A list of commercial imaging satellites built by Orbital is provided next. Orbital built Science and Environmental satellites conduct astrophysics , Remote sensing/Earth Observation , heliophysics , planetary exploration and technology demonstration missions. These satellites are built on Orbital's LEOStar-1,-2, or -3 satellite platforms depending on
12180-402: Was 21 W/cm . For Viking 1 , the TPS acted as a charred thermal insulator and never experienced significant ablation. Viking 1 was the first Mars lander and based upon a very conservative design. The Viking aeroshell had a base diameter of 3.54 meters (the largest used on Mars until Mars Science Laboratory). SLA-561V is applied by packing the ablative material into a honeycomb core that
12296-430: Was an American company specializing in the design, manufacture, and launch of small- and medium- class space and launch vehicle systems for commercial, military and other government customers. In 2014, Orbital merged with Alliant Techsystems (ATK) to create a new company called Orbital ATK , which in turn was purchased by Northrop Grumman in 2018. Orbital was headquartered in Dulles, Virginia and publicly traded on
12412-418: Was controlled through a split body flap (also called a split-windward flap ) along with two yaw flaps mounted on the vehicle's sides. Hydraulic actuation was used for controlling the flaps. AMaRV was guided by a fully autonomous navigation system designed for evading anti-ballistic missile (ABM) interception. The McDonnell Douglas DC-X (also a biconic) was essentially a scaled-up version of AMaRV. AMaRV and
12528-657: Was developed by SpaceX in 2006–2010 for the Dragon space capsule . The first reentry test of a PICA-X heat shield was on the Dragon C1 mission on 8 December 2010. The PICA-X heat shield was designed, developed and fully qualified by a small team of a dozen engineers and technicians in less than four years. PICA-X is ten times less expensive to manufacture than the NASA PICA heat shield material. A second enhanced version of PICA—called PICA-3—was developed by SpaceX during
12644-544: Was just sufficiently understood to ensure Apollo's success. However, radiative heat flux in carbon dioxide (Mars entry) is still barely understood and will require major research. The frozen gas model describes a special case of a gas that is not in equilibrium. The name "frozen gas" can be misleading. A frozen gas is not "frozen" like ice is frozen water. Rather a frozen gas is "frozen" in time (all chemical reactions are assumed to have stopped). Chemical reactions are normally driven by collisions between molecules. If gas pressure
12760-521: Was later sold off in 2000. In 1997, Orbital acquired CTA, Inc, a company that, under the spacecraft design engineering and business leadership of Tom van der Heyden - designer of the GEOStar spacecraft - had designed and built the first geostationary "lightsat" under contract to Indonesia for Asia's first Direct Broadcast Satellite (DBS) television broadcast program, and the world's first S-Band television broadcast satellite - providing an entry into
12876-480: Was launched on an eight-year, three-billion-mile journey to the main asteroid belt between Mars and Jupiter. A major milestone in the company's history was in 2008 when it received a long-term NASA contract to provide cargo transportation services to and from the International Space Station (ISS) with a value of approximately US$ 1.9 billion for missions from 2011 to 2015. Orbital used its Cygnus spacecraft and Antares launch vehicle to transport cargo to ISS following
12992-498: Was possible. However, the Mk-6 was a huge RV with an entry mass of 3,360 kg, a length of 3.1 m and a half-angle of 12.5°. Subsequent advances in nuclear weapon and ablative TPS design allowed RVs to become significantly smaller with a further reduced bluntness ratio compared to the Mk-6. Since the 1960s, the sphere-cone has become the preferred geometry for modern ICBM RVs with typical half-angles being between 10° and 11°. Reconnaissance satellite RVs (recovery vehicles) also used
13108-519: Was rolled back to the HIF and time-sensitive cargo removed. The launch date was rescheduled for no earlier than 13 January 2014, but was later moved forward to 7 January 2014 after a scheduling conflict at Wallops was resolved. The launch was delayed one day due to cold temperatures at the launch site. NASA Wallops and Orbital Sciences announced the launch attempt on 8 January 2014 was scrubbed due to "an unusually high level of space radiation that exceeded by
13224-604: Was the Mk-2 RV (reentry vehicle), which was developed in 1955 by the General Electric Corp. The Mk-2's design was derived from blunt-body theory and used a radiatively cooled thermal protection system (TPS) based upon a metallic heat shield (the different TPS types are later described in this article). The Mk-2 had significant defects as a weapon delivery system, i.e., it loitered too long in the upper atmosphere due to its lower ballistic coefficient and also trailed
13340-612: Was the maiden flight of the Castor 30B second stage . Orbital Sciences continued its naming of Cygnus spacecraft in tribute to former astronauts. This vehicle was named the S.S. C. Gordon Fullerton for C. Gordon Fullerton , the NASA astronaut who died on 21 August 2013. This Cygnus cargo mission launched the Nanoracks CubeSat Deployer to the ISS's Kibō module . The launch of Orb-1 was scheduled for November 2013, but
13456-483: Was written by Bonnie J. McBride and Sanford Gordon at NASA Lewis (now renamed "NASA Glenn Research Center"). Other names for CEA are the "Gordon and McBride Code" and the "Lewis Code". CEA is quite accurate up to 10,000 K for planetary atmospheric gases, but unusable beyond 20,000 K ( double ionization is not modelled). CEA can be downloaded from the Internet along with full documentation and will compile on Linux under
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