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The configurations shown all employ an element of regenerative cooling. Fuel or oxidizer may be used as a coolant, flowing through a jacket surrounding the thrust chamber. The heat absorbed in this way, necessary in prolonged firings, enhances the initial energy content of the propellants prior to injection into the combustion chamber. By contrast, solid-propellant rockets are comparatively inflexible in their design. The gross classification of solid rockets is made on the basis of the...

Specifying The Orbit

The orbit equation (4.4) is equivalent to a sixth-order scalar differentia equation that requires six initial conditions in order to determine the six constants of integration. At orbit injection these will be the three components of position and of velocity. A standard way of specifying an orbit is to use orbital elements, which refer the orbit to a frame of reference that is fixed relative to the stars. This is used both for astronomy and for satellites. The frame of reference that is...

Transmitters

There arc only two generally accepted means of amplifying the signals to the level required for downlink transmission. These are the TWT and power transistors. The TWT is the most commonly used but as transistor technology improves, solid-state amplifiers are finding an increasing number of applications, mainly because of their higher reliability and lower mass. TWTs, however, are currently the only choice of transmitters at high power levels, particularly at the higher frequency bands....

Eumetsat 643

European Communications Satellite (ECS) 367 Standardization (ECSS) 476 European Retrievable Carrier (EURECA) 381-2 European solar observatory SOHO 107 European Space Agency (ESA) 155,201. 222, 325, 526, 642 Eurostar 3000 configuration 274-5 structure 271 exhaust flow patterns 177 exit-to-throat area ratio 176 externa couple 59 external disturbance torques 60 externa forces 52 fail-operational fail-safe system 571 failure mode effects and criticality analysis (FMECA) 556,566,567,573 failure...

Solidpropellant apogee motors

In the emplacement sequence for a communications spacecraft into geostationary orbit using an expendable launch vehicle such as Ariane, the final stage injects the satellite into an elliptical transfer orbit with apogee at geostationary height. The circularization manoeuvre is often achieved through a high thrust, short duration burn from a solid propellant apogee boost (or kick) motor. For a satellite with an on-station mass of approximately 1000kg, the necessary apogee motor fuel approaches...

Slip rings

There are a number of space mechanisms in which an electric current must be transmitted across a rotating joint, the SAD being an obvious example. In the case of the HST, the rotation of the solar array was limited to 340 to avoid sunlight entering the telescope, so a wire harness could be used. For complete rotation, slip rings are needed. These may be axial, as in Figure 15.12, or radial in the form of a disc (see Figure 15.20), but the material Figure 15.20 Pancake slip ring (Reproduced by...

Launch vehicle interface

The selection of a launch vehicle plays a major role in setting geometric and mass limits on the design. Some launchers have the capability of launching more than one spacecraft at a time. Figure 8.1 shows an arrangement for a dual launch on Ariane. Note that there is no connection between the fairing and the spacecraft. All accelerations and consequent inertia loads (except acoustic) are imparted to the spacecraft via the launch vehicle interface. There are similar arrangements for triple...

Mechanisms for deployable structures

Various types of mechanisms can be used in order to deploy elements of the spacecraft, which are generally referred to as appendages. The simplest method to deploy an appendage is to use a knuckle joint located at the root of the appendage. This joint can be a simple hinge coupled with a torsional spring. An example of this is shown in Figure 1S.3, which is used to deploy a whip antenna. The torsional spring forces the rotation of the hinge, driving the deployment of the antenna and keeping the...

The spinning spacecraft

The dynamics of a spinner are covered in Section 3.4.2 of Chapter 3. It is assumed here that the vehicle is spinning about its z-axis with an angular rate S, and that its mass distribution is axially symmetric so that w. The response to a torque will be of interest in one or both of the two sets of axes. A typical 'spinner' is shown in Figure 9.4. The response in axes fixed in the structure will be of interest when the torque components are in these axes or when the attitude sensors measure...

Cots Components In The Space Environment

The space environment (see also Chapter 2) can be particularly harmful to COTS devices. Once in orbit, the devices will experience high-vacuum conditions, potentially extreme hot or extreme cold temperature conditions, and relatively high levels of ionizing radiation. Many COTS parts contain plastic materials, which may out-gas under vacuum (see Section 2.4.1 of Chapter 2). These either cannot be flown or require further encapsulation before they can do so. The plastics used to encapsulate...

Microsatellite Platforms

The first modem microsatellites such as UoSAT-1, shown in Figure 18.7, used a conventional mechanical structure with electronic module boxes clustered around a central thrust column. Solar panels were body-mounted to stringers supported from the end (Z-facet) honeycomb panels. However, the need to accommodate a variety of payload customers within a standard launcher envelope, coupled with increased demands on packing density, electromagnetic compatibility, economy of manufacture and ease of...

Intelsat VI spacecraft design

The two consortia bidding for the Intelsat VI contract proposed very different solutions based on their particular expertise. Ford proposed a three-axis-stabilized solution like their Intelsat V design, although considerably larger, to accommodate the larger antennas and the higher power required. Hughes proposed a spinning spacecraft with a despun platform like the Intelsat IV solution. In April 1982, Hughes was awarded a 700 million contract to build five satellites with an option for six...

Tracking and data relay satellite system TDRSS

In the early 1980s, NASA set up space-based systems for Tracking, Telemetry and Command TT amp C between ground and space, with the tracking and data relay satellite system TDRSS . TDRSS comprises six operational satellites and one in-orbit spare. The operational ones are separated by 130 of longitude, two at 41 W and two at 171 W, and axe 22.5 45 east-west 310 61 north-south for 100 coverage for both MA and SA users Figure 14.4 TDRSS configuration and coverage limits Required SA J J antenna...