Misplaced Pages

#213786

54-417: The name apogee engine derives from the type of manoeuvre for which the engine is typically used, i.e. an in-space delta- v change made at the apogee of an elliptical orbit in order to circularise it. For geostationary satellites , this type of orbital manoeuvre is performed to transition from a geostationary transfer orbit and place the satellite on station in a circular geostationary orbit . Despite

108-406: A hydrazine thruster) the capacity of the reaction control system is Δ v = 2100   ln ⁡ ( 1 0.8 ) m/s = 460 m/s . {\displaystyle \Delta {v}=2100\ \ln \left({\frac {1}{0.8}}\right)\,{\text{m/s}}=460\,{\text{m/s}}.} If v exh {\displaystyle v_{\text{exh}}}

162-408: A "US person" who wants to export USML items to a "foreign person" must obtain authorization from the U.S. Department of State before the export can take place. A "U.S. person" can be A foreign person is any person who is not a lawful permanent resident of the U.S. and includes foreign governments and organizations. This means that, for example, a foreign person who is visiting the U.S. will remain

216-766: A foreign person for the purposes of ITAR and any export of USML items to them inside the U.S. must be subject to an export authorization. This is similar to the concept of "Deemed Exports" used by the Bureau of Industry and Security within the Department of Commerce in administration of the Export Administration Regulations although the Department of State does not use the term "Deemed Export" (see also "Restrictions on Dual and Third Country Nationals below"). The export authorization may take

270-444: A part in the decision. Delta-V Delta- v (also known as " change in velocity "), symbolized as Δ v {\textstyle {\Delta v}} and pronounced /dɛltə viː/ , as used in spacecraft flight dynamics , is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or landing on a planet or moon, or an in-space orbital maneuver . It

324-533: A report from Space Review . In early 2013 legislation was passed allowing the removal of satellite technology from ITAR regulation. The ITAR regulate defense articles and defense services. Defense articles can be broken down into two categories: (a) physical items (often referred to as "commodities") and (b) technical data. The ITAR contain a list of defense articles called the US Munitions List ("USML"), which can be found at 22 CFR §121.1 . The USML

378-410: Is a scalar that has the units of speed . As used in this context, it is not the same as the physical change in velocity of said spacecraft. A simple example might be the case of a conventional rocket-propelled spacecraft, which achieves thrust by burning fuel. Such a spacecraft's delta- v , then, would be the change in velocity that spacecraft can achieve by burning its entire fuel load. Delta- v

432-428: Is a non-constant function of the amount of fuel left v exh = v exh ( m ) {\displaystyle v_{\text{exh}}=v_{\text{exh}}(m)} the capacity of the reaction control system is computed by the integral ( 5 ). The acceleration ( 2 ) caused by the thruster force is just an additional acceleration to be added to the other accelerations (force per unit mass) affecting

486-422: Is also notable that large thrust can reduce gravity drag . Delta- v is also required to keep satellites in orbit and is expended in propulsive orbital stationkeeping maneuvers. Since the propellant load on most satellites cannot be replenished, the amount of propellant initially loaded on a satellite may well determine its useful lifetime. From power considerations, it turns out that when applying delta- v in

540-508: Is an assault rifle used by the U.S. military, would be identified under Category I paragraph (b): *(b) Fully automatic firearms to .50 caliber inclusive (12.7 mm). A flash suppressor for the M4 rifle then follows in paragraph (e): *(e) Silencers, mufflers, sound and flash suppressors for the articles in (a) through (d) of this category and their specifically designed, modified or adapted components and parts. Components, parts, and accessories for

594-445: Is an exponential function of delta- v in accordance with the rocket equation , it will also depend on the exhaust velocity. It is not possible to determine delta- v requirements from conservation of energy by considering only the total energy of the vehicle in the initial and final orbits since energy is carried away in the exhaust (see also below). For example, most spacecraft are launched in an orbit with inclination fairly near to

SECTION 10

#1732794535214

648-1330: Is broken down into the following categories: I: Firearms , close assault weapons and combat shotguns II: Guns and armament III: Ammunition /ordnance IV: Launch vehicles , Guided missiles , ballistic missiles , rockets , torpedoes , bombs and mines V: Explosives and energetic materials, propellants , incendiary agents and their constituents VI: Surface vessels of war and special naval equipment VII: Tanks and military vehicles VIII: Aircraft and associated equipment IX: Military training equipment X: Personal Protective Equipment XI: Military electronics XII: Fire control , range finders , optical and guidance and control equipment XIII: Materials and miscellaneous equipment XIV: Toxicological agents, including chemical agents , biological agents , and associated equipment XV: Spacecraft and associated equipment XVI: Nuclear weapons related articles XVII: Classified articles , technical data and defense services not otherwise enumerated XVIII: Directed energy weapons XIX: Gas turbine engines and associated equipment XX: Submersible vessels , oceanographic and related articles XXI: Articles, technical data, and defense services not otherwise enumerated For example, an M4 carbine , which

702-423: Is dictated by the useful life of the materials of construction, primarily those used for the combustion chamber. A simplified division can be made between apogee engines used for telecommunications and exploration missions: The actual engine chosen for a mission is dependent on the technical details of the mission. More practical considerations such as cost, lead time and export restrictions (e.g. ITAR ) also play

756-428: Is even more so when the planet is a large one with a deep gravity field, such as Jupiter. Due to the relative positions of planets changing over time, different delta-vs are required at different launch dates. A diagram that shows the required delta- v plotted against time is sometimes called a porkchop plot . Such a diagram is useful since it enables calculation of a launch window , since launch should only occur when

810-613: Is in the public domain. Nor does it apply to general marketing information or basic system descriptions. Broad interpretations of these exceptions have faced several legal challenges. For example, college professors have been prosecuted for breaches of the AECA as a result of access to USML items by foreign graduate students and companies have been penalized for alleged breaches of the AECA for failing to properly remove USML items from material used to market defense articles. The U.S. government has also taken action (albeit unsuccessfully) for

864-465: Is just the rocket equation applied to the sum of the two maneuvers. This is convenient since it means that delta- v can be calculated and simply added and the mass ratio calculated only for the overall vehicle for the entire mission. Thus delta- v is commonly quoted rather than mass ratios which would require multiplication. When designing a trajectory, delta- v budget is used as a good indicator of how much propellant will be required. Propellant usage

918-430: Is mapped over a range of operating conditions before being deemed flight-qualified . This means that a flight-qualified production engine can be tuned (within reason) by the manufacturer to meet particular mission requirements, such as higher thrust. Most apogee engines are operated in an on–off manner at a fixed thrust level. This is because the valves used only have two positions: open or closed. The duration for which

972-459: Is produced by reaction engines , such as rocket engines , and is proportional to the thrust per unit mass and the burn time. It is used to determine the mass of propellant required for the given maneuver through the Tsiolkovsky rocket equation . For multiple maneuvers, delta- v sums linearly. For interplanetary missions, delta- v is often plotted on a porkchop plot , which displays

1026-407: Is the coordinate acceleration. When thrust is applied in a constant direction ( ⁠ v / | v | ⁠ is constant) this simplifies to: Δ v = | v 1 − v 0 | {\displaystyle \Delta {v}=|v_{1}-v_{0}|} which is simply the magnitude of the change in velocity . However, this relation does not hold in

1080-500: Is usually quoted in terms of vacuum specific impulse and vacuum thrust. However, there are many other details which influence performance: A typical 500 N-class hypergolic liquid apogee engine has a vacuum specific impulse in the region of 320 s, with the practical limit estimated to be near 335 s. Though marketed to deliver a particular nominal thrust and nominal specific impulse at nominal propellant feed conditions, these engines actually undergo rigorous testing where performance

1134-572: The Code of Federal Regulations . The Department of State Directorate of Defense Trade Controls (DDTC) interprets and enforces ITAR. The related Export Administration Regulations (Code of Federal Regulations Title 15 chapter VII, subchapter C) are enforced and interpreted by the Bureau of Industry and Security in the Commerce Department. The Department of Defense is also involved in the review and approval process. Physical enforcement of

SECTION 20

#1732794535214

1188-697: The Export Administration Regulations , which cover items that may have uses in defense articles (such as a radar component used in a certain missile). Defense-related articles and services on the United States Munitions List (USML) are covered by the ITAR, which implement the provisions of the Arms Export Control Act (AECA), and are described in Title 22 (Foreign Relations), Chapter I ( Department of State ), Subchapter M of

1242-508: The vacuum I sp is used for calculating the vehicle's delta- v capacity via the rocket equation . In addition, the costs for atmospheric losses and gravity drag are added into the delta- v budget when dealing with launches from a planetary surface. Orbit maneuvers are made by firing a thruster to produce a reaction force acting on the spacecraft. The size of this force will be where The acceleration v ˙ {\displaystyle {\dot {v}}} of

1296-473: The ITAR (as well as all import and export laws of the United States) is performed by Homeland Security Investigations Special Agents (formerly U.S. Customs) under Immigration and Customs Enforcement , an agency of the Department of Homeland Security . For practical purposes, ITAR regulations dictate that information and material pertaining to defense and military-related technologies (items listed on

1350-493: The M4 are in paragraph (h): (h) Components, parts, accessories and attachments for the articles in paragraphs (a) through (g) of this category. Finally, technical data and defense services relating to the M4 are in paragraph (i): (i) Technical data (as defined in §120.33 of this subchapter) and defense services (as defined in §120.32 of this subchapter) directly related to the defense articles described in paragraphs (a) through (h) of this category. Technical data directly related to

1404-968: The Soyuz spacecraft makes a de-orbit from the ISS in two steps. First, it needs a delta- v of 2.18 m/s for a safe separation from the space station. Then it needs another 128 m/s for reentry . International Traffic in Arms Regulations International Traffic in Arms Regulations ( ITAR ) is a set of U.S. Department of State regulations that control the export of defense and military technologies to safeguard national security and further its foreign policy objectives. The United States government has adopted two types of regulations to control exports of military-relevant items: ITAR, which cover weapons and defense articles specifically (such as missiles ); and

1458-553: The U.S. Another change occurred as a result of Space Systems/Loral 's conduct after the February 1996 failed launch of the Intelsat 708 satellite. The Department of State charged Space Systems/Loral with violating the Arms Export Control Act and the ITAR. ITAR does not apply to information related to general scientific, mathematical or engineering principles that are commonly taught in schools and colleges or information that

1512-650: The U.S. Department of State took over export regulations for satellites. The U.S. Department of State has published 29 instances of Consent Agreements (agreements entered into by parties charged with breaches of ITAR) since 1999. This compares to 12 Consent Agreements in the preceding 22 years. ITAR's prominence has also increased as its implications for foreign parties that handle USML items have become better understood (see "Controversy" below). ITAR's impact of increased regulations also meant America's worldwide market share in satellite technology declined from 83 percent to 50 percent in 2008, states The Economist , which cited

1566-575: The U.S. Munitions List) may only be shared with US persons unless authorization from the Department of State is received to export the material or information to a foreign person. US persons (including organizations; see legal personality ) can face heavy fines if they have, without authorization or the use of an exemption, provided foreign persons with access to ITAR-protected defense articles, services or technical data. The U.S. Munitions List changes over time. Until 1996–1997, ITAR classified strong cryptography as arms and prohibited their export from

1620-486: The USML, are required to register with U.S. Department of State. Registration is primarily a means to provide the U.S. Government with necessary information on who is involved in certain manufacturing and exporting activities. Registration does not confer any export rights or privileges, but is a precondition for the issuance of any license or other approval for export. Registration fees start at US$ 2,250 per year. Under ITAR,

1674-540: The ability for reignition. In many instances mixed oxides of nitrogen (MON), such as MON-3 ( N 2 O 4 with 3 wt% NO ), is used as a substitute for pure N 2 O 4 . The use of N 2 H 4 is under threat in Europe due to REACH regulations. In 2011 the REACH framework legislation added N 2 H 4 to its candidate list of substances of very high concern . This step increases

Liquid apogee engine - Misplaced Pages Continue

1728-632: The change in momentum ( impulse ), where: Δ p = m Δ v {\displaystyle \Delta \mathbf {p} =m\Delta \mathbf {v} } , where p {\displaystyle \mathbf {p} } is momentum and m is mass. In the absence of external forces: Δ v = ∫ t 0 t 1 | v ˙ | d t {\displaystyle \Delta {v}=\int _{t_{0}}^{t_{1}}\left|{\dot {v}}\right|\,dt} where v ˙ {\displaystyle {\dot {v}}}

1782-558: The direction of the velocity the specific orbital energy gained per unit delta- v is equal to the instantaneous speed. This is called the Oberth effect. For example, a satellite in an elliptical orbit is boosted more efficiently at high speed (that is, small altitude) than at low speed (that is, high altitude). Another example is that when a vehicle is making a pass of a planet, burning the propellant at closest approach rather than further out gives significantly higher final speed, and this

1836-405: The engine is on, sometimes referred to as the burn duration , depends both on the manoeuvre and the capability of the engine. Engines are qualified for a certain minimal and maximal single-burn duration. Engines are also qualified to deliver a maximal cumulative burn duration, sometimes referred to as cumulative propellant throughput . The useful life of an engine at a particular performance level

1890-622: The export of technical data that was allegedly already publicly available on the Internet. The AECA and ITAR were enacted in 1976 during the Cold War with the USSR and were intended to implement unilateral arms export controls that reflected those imposed on Eastern Bloc countries by the multilateral Coordinating Committee for Multilateral Export Controls . U.S. Government enforcement activities have increased dramatically since 1999, when

1944-598: The form of blueprints, drawings, photographs, plans, instructions or documentation. (2) Classified information relating to defense articles and defense services on the U.S. Munitions List and 600-series items controlled by the Commerce Control List; (3) Information covered by an invention secrecy order; or (4) Software ( see 22 CFR §120.40(g) ) directly related to defense articles. All U.S. manufacturers, exporters, and brokers of defense articles, defense services, or related technical data, as defined on

1998-403: The general case: if, for instance, a constant, unidirectional acceleration is reversed after ( t 1 − t 0 )/2 then the velocity difference is 0, but delta- v is the same as for the non-reversed thrust. For rockets, "absence of external forces" is taken to mean the absence of gravity drag and atmospheric drag, as well as the absence of aerostatic back pressure on the nozzle, and hence

2052-482: The integration variable from time t to the spacecraft mass m one gets Assuming v exh {\displaystyle v_{\text{exh}}\,} to be a constant not depending on the amount of fuel left this relation is integrated to which is the Tsiolkovsky rocket equation . If for example 20% of the launch mass is fuel giving a constant v exh {\displaystyle v_{\text{exh}}} of 2100 m/s (a typical value for

2106-499: The latitude at the launch site, to take advantage of the Earth's rotational surface speed. If it is necessary, for mission-based reasons, to put the spacecraft in an orbit of different inclination , a substantial delta- v is required, though the specific kinetic and potential energies in the final orbit and the initial orbit are equal. When rocket thrust is applied in short bursts the other sources of acceleration may be negligible, and

2160-487: The magnitude of the velocity change of one burst may be simply approximated by the delta- v . The total delta- v to be applied can then simply be found by addition of each of the delta- v' s needed at the discrete burns, even though between bursts the magnitude and direction of the velocity changes due to gravity, e.g. in an elliptic orbit . For examples of calculating delta- v , see Hohmann transfer orbit , gravitational slingshot , and Interplanetary Transport Network . It

2214-488: The maneuver as a shift from one Kepler orbit to another by an instantaneous change of the velocity vector. This approximation with impulsive maneuvers is in most cases very accurate, at least when chemical propulsion is used. For low thrust systems, typically electrical propulsion systems, this approximation is less accurate. But even for geostationary spacecraft using electrical propulsion for out-of-plane control with thruster burn periods extending over several hours around

Liquid apogee engine - Misplaced Pages Continue

2268-508: The manufacture or production of any defense articles described elsewhere in this category that are designated as Significant Military Equipment (SME) shall itself be designated SME. Technical data is defined in the ITAR at 22 CFR §120.33 as: (1) Information, other than software as defined in 22 CFR §120.40(g) , which is required for the design, development, production, manufacture, assembly, operation, repair, testing, maintenance or modification of defense articles. This includes information in

2322-721: The mass ratios of the maneuvers, and v 1 , v 2 are the delta- v of the first and second maneuvers m 1 m 2 = e V 1 / V e e V 2 / V e = e V 1 + V 2 V e = e V / V e = M {\displaystyle {\begin{aligned}m_{1}m_{2}&=e^{V_{1}/V_{e}}e^{V_{2}/V_{e}}\\&=e^{\frac {V_{1}+V_{2}}{V_{e}}}\\&=e^{V/V_{e}}=M\end{aligned}}} where V = v 1 + v 2 and M = m 1 m 2 . This

2376-533: The mission is within the capabilities of the vehicle to be employed. Delta- v needed for various orbital manoeuvers using conventional rockets; red arrows show where optional aerobraking can be performed in that particular direction, black numbers give delta- v in km/s that apply in either direction. Lower-delta- v transfers than shown can often be achieved, but involve rare transfer windows or take significantly longer, see: Orbital mechanics § Interplanetary Transport Network and fuzzy orbits . For example

2430-426: The name, an apogee engine can be used for a range of other manoeuvres, such as end-of-life deorbit, Earth orbit escape, planetary orbit insertion and planetary descent/ascent. In some parts of the space industry an LAE is also referred to as a liquid apogee motor (LAM), a liquid apogee thruster (LAT) and, depending on the propellant, a dual-mode liquid apogee thruster (DMLAT). Despite the ambiguity with respect to

2484-439: The nodes this approximation is fair. Delta- v is typically provided by the thrust of a rocket engine , but can be created by other engines. The time-rate of change of delta- v is the magnitude of the acceleration caused by the engines , i.e., the thrust per total vehicle mass. The actual acceleration vector would be found by adding thrust per mass on to the gravity vector and the vectors representing any other forces acting on

2538-399: The object. The total delta- v needed is a good starting point for early design decisions since consideration of the added complexities are deferred to later times in the design process. The rocket equation shows that the required amount of propellant dramatically increases with increasing delta- v . Therefore, in modern spacecraft propulsion systems considerable study is put into reducing

2592-406: The required mission delta- v as a function of launch date. Δ v = ∫ t 0 t 1 | T ( t ) | m ( t ) d t {\displaystyle \Delta {v}=\int _{t_{0}}^{t_{1}}{\frac {|T(t)|}{m(t)}}\,dt} where Change in velocity is useful in many cases, such as determining

2646-566: The risk that the use of N 2 H 4 will be prohibited or restricted in the near- to mid-term. Exemptions are being sought to allow N 2 H 4 to be used for space applications, however to mitigate this risk, companies are investigating alternative propellants and engine designs. A change over to these alternative propellants is not straightforward, and issues such as performance, reliability and compatibility (e.g. satellite propulsion system and launch-site infrastructure) require investigation. The performance of an apogee engine

2700-435: The spacecraft and the orbit can easily be propagated with a numerical algorithm including also this thruster force. But for many purposes, typically for studies or for maneuver optimization, they are approximated by impulsive maneuvers as illustrated in figure 1 with a Δ v {\displaystyle \Delta {v}} as given by ( 4 ). Like this one can for example use a "patched conics" approach modeling

2754-492: The spacecraft caused by this force will be where m is the mass of the spacecraft During the burn the mass of the spacecraft will decrease due to use of fuel, the time derivative of the mass being If now the direction of the force, i.e. the direction of the nozzle , is fixed during the burn one gets the velocity increase from the thruster force of a burn starting at time t 0 {\displaystyle t_{0}\,} and ending at t 1 as Changing

SECTION 50

#1732794535214

2808-425: The spacecraft from the radiant heat of the combustion chamber, these engines are generally installed together with a heat shield . Apogee engines typically use one fuel and one oxidizer. This propellant is usually, but not restricted to, a hypergolic combination such as: Hypergolic propellant combinations ignite upon contact within the engine combustion chamber and offer very high ignition reliability, as well as

2862-483: The total delta- v needed for a given spaceflight, as well as designing spacecraft that are capable of producing larger delta- v . Increasing the delta- v provided by a propulsion system can be achieved by: Because the mass ratios apply to any given burn, when multiple maneuvers are performed in sequence, the mass ratios multiply. Thus it can be shown that, provided the exhaust velocity is fixed, this means that delta- v can be summed: When m 1 , m 2 are

2916-799: The use of engine and motor in these names, all use liquid propellant. An apogee kick motor (AKM) or apogee boost motor (ABM) such as the Waxwing , however, uses solid propellant. These solid-propellant versions are not used on new-generation satellites. The apogee engine traces its origin to the early 1960s, when companies such as Aerojet , Rocketdyne , Reaction Motors , Bell Aerosystems , TRW Inc. and The Marquardt Company were all participants in developing engines for various satellites and spacecraft. Derivatives of these original engines are still used today and are continually being evolved and adapted for new applications. A typical liquid apogee engine scheme could be defined as an engine with: To protect

#213786