Upper stage

AP = pressure drop through the upper stage distributor and bed. ... 

For the 90% 235U example, taking h = 1 s, tp 30 days. For squared-off cascades tp is longer because more enriched material is required in the upper stages. 

Because of the very large enrichments required in heavy water production, cascades taper markedly. In the upper stages the relative advantage of chemical exchange over water distillation vanishes. Most heavy water plants carry out the last portion of the enrichment by distillation (from 20% or 30% D to 99.85%). Accordingly both exchange and distillation will be briefly treated below. First, however, to clarify the important distinction between chemical and thermal reflux we treat an example of isotope separation using chemical reflux. 

F-0 mixts (Flox) with light hydrocarbon (HC) fuels as rocket propints for upper-stage applications show the unique ability to provide high performance, space storability, hypergolicity, current availability, high d, and capability for both transpiration regenerative cooling. 

Economic Factors. Economic factors are related to the availability and cost of the propellant as well as the cost of the equipment required to transport, store, and supply the propellant. Generally, low cost is a prime requisite for a propellant which will be utilized in large quantities and/or in multiunits (i.e., booster stages of launch vehicles and in military weapons). However, where utilization of a high-cost propellant may be required to complete the mission, the cost factor can be of secondary importance. This situation is usually associated with upper stages of a space launch vehicle. 

Space exploration application areas can be further subdivided— namely, booster propulsion, upper stage propulsion, and spacecraft control propulsion. The requirements in each of these general areas are different. 

Upper stage propellant applications are usually based primarily on performance—i.e., high specific impulse. If the upper stage is a multistart vehicle, hypergolicity is usually required. Careful consideration is also given to the propellant physical and chemical stability as well as to the matching of the propellant s liquidus range to the space environmental temperature if the propellant system is to remain operational in space... 

Butts, P.G., and Hammond, R.N., (1983) Inertial upper stage (IUS) propellant development and qualification, in JANNAF Propulsion Meeting, vol. I, (ed. 

Fig. 6.4. Cross-section of a metal diffusion pump. The upper stage in this pump has a wide annular opening (A) which provides a good ultimate vacuum. The lower stage has a small annular opening (A ) so the pump will operate against a high fore pressure. (B) High-vacuum connection to the low-temperature trap and vacuum line. (C) Connection to rotary oil-sealed pump. This pump is cooled by means of water tubes (D). Air-cooled versions have fins in place of these tubes and a fan is installed to blow air over these fins. (E) Electrically heated oil reservoir.

Plotting Eq. (10.112) will also show that any rate of discharge less than the maximum can occur at two different depths for a given value of specific energy. If the flow is on the upper limb of the curve, it is said to be upper-stage or tranquil if on the lower limb, it is called lower-stage or shooting. 

The velocity and rate of discharge occurring at the critical depth are termed Vc and qc = qmax, the critical velocity and flow, respectively. On account of the greater area, the velocity of upper-stage flow is slower than the critical and is called subcritical velocity likewise, supercritical velocity occurs at lower-stage conditions. Combining Eqs. (10.110) and (10.113) yields a simple expression for critical velocity,... 

The M3 scenario. This occurs because of an upstream control, as by the sluice gate. The bed slope is not sufficient to sustain lower-stage flow, and, at a certain point determined by energy and momentum relations, the water surface will pass through a hydraulic jump to upper-stage flow unless this is made unnecessary by the existence of a free overfall before the M3 crest reaches critical depth. 

The S scenarios. These are steep slope cases. They may be analyzed in much the same fashion as the M scenarios, having due regard for downstream control in the case of upper-stage flow and upstream control for lower-stage flow. Thus a dam or an obstruction on a steep slope produces an Si scenario, which approaches the horizontal asymptotically but cannot so approach the uniform depth line, which lies below the critical depth. Therefore this curve must be preceded by a hydraulic jump. The S2 scenario shows accelerated lower-stage flow, smoothly... 

By far the most important of the local nonuniform flow phenomena is that which occurs when supercritical flow has its velocity reduced to subcritical. We have seen in these example scenarios that there is no ordinary means of changing from lower- to upper-stage flow with a smooth transition, because the theory calls for a vertical slope of the water surface. The result, then, is a marked discontinuity in the surface, characterized by a steep upward slope of the profile, broken throughout with violent turbulence, and known universally as the hydraulic jump. 

M. Mochizuki, "Solid Motor and Propellant for Upper Stage of H-l Rocket 1." Industrial Explosives (Not yet printed)... 

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