Fuels space shuttle

Stoichiometry has important practical applications, such as predicting how much product can be formed in a reaction. For example, in the space shuttle fuel cell, oxygen reacts with hydrogen to produce water, which is used for life support (Fig. L.l). Let s look at the calculation space shuttle engineers would have to do to find out how much water is formed when 0.25 mol 02 reacts with hydrogen gas. 

PROBLEM 14.19 The space shuttle fuel tank contains 1.45 X 106 L of liquid hydrogen, which has a density of 0.088 g/L. How much heat (in kilojoules) is liberated when the hydrogen burns in an excess of oxygen How many kilograms of oxygen are needed to oxidize the hydrogen ... 

Consider the two space shuttle fuel reactions in Exercises 81 and 82. Which reaction produces more energy per kilogram of reactant mixture (stoichiometric amounts) ... 

Fuel cells deliver as much power as batteries weighing ten times as much. On a typical seven-day mission, the space shuttle fuel cells consumed 1500 pounds of hydrogen and generated 190 gallons of water. 

Typical polarization curves for alkaline fuel cells are shown in Fig, 27-63, It is apparent that the all aline fuel cell can operate at about 0,9 and 5()() rnA/cnr current density. This corresponds to an energy conversion efficiency of about 60 percent IIII, The space shuttle orbiter powder module consists of three separate units, each measuring 0,35 by 0,38 by I rn (14 by 15 by 40 in), weighing 119 kg (262 lb), and generating 15 kW of powder. The powder density is about 100 W/L and the specific powder, 100 W/kg,... 

May 4, 1988, explosions leveled a Pacific Engineering Production Co. (PEPCO) plant, at Henderson, NV, one of only two U.S. plants producing 20 million lb/ year (maximum of 40 million Ib/year - see Table 7.1-2) ammonium perchlorate for solid rocket fuel. It was the principal supplier for the space shuttle and sole supplier for the Titan rocket and several military missiles. 

A final, somewhat variable outlet for large-scale liquid oxygen is as oxidant in rocket fuels for space exploration, satellite launching and space shuttles. For example, in the Apollo mission to the moon (1979), each Saturn 5 launch rocket used 1270 m (i.e. 1.25 million litres or 1450 tonnes) of liquid oxygen in Stage 1, where it oxidized the kerosene fuel (195 000 1, or about 550 tonnes) in the almost unbelievably short time of 2.5 min. Stages 2 and 3 had 315 and 76.3 m of liquid O2 respectively, and the fuel was liquid FI2. 

FIGURE L.l One of the three hydrogen-oxygen fuel cells used on the space shuttle to provide life-support electricity and drinking water. 

L.3 The solid fuel in the booster stage of the space shuttle is a mixture of ammonium perchlorate and aluminum powder. On ignition, the reaction that takes place is 6 NH4C104(s) +... 

Self-Test 4.12B The reaction of H2 and 02 gases to produce liquid H20 is used in fuel cells on the space shuttles to provide electricity. What mass of water is produced in the reaction of 100.0 L of oxygen stored at 25°C and 1.00 atm ... 

FIGURE 6.27 In this preparation of rocket fuel for the space shuttle, powdered aluminum is mixed with an oxidizing agent in a liquid polymer base that hardens inside the booster rocket shell. 

The problem was solved by Francis Bacon, a British scientist and engineer, who developed an idea proposed by Sir William Grove in 18.39. A fuel cell generates electricity directly from a chemical reaction, as in a battery, but uses reactants that are supplied continuously, as in an engine. A fuel cell that runs on hydrogen and oxygen is currently installed on the space shuttle (see Fig. L.l). An advantage of this fuel cell is that the only product of the cell reaction, water, can be used for life support. 

The hydrogen-oxygen cell used in the space shuttle is called an alkali fuel cell, because it has an alkaline electrolyte ... 

One spectacular example of the oxidizing ability of perchlorates is their use in the booster rockets of space shuttles. The solid propellant consists of aluminum powder (the fuel), ammonium perchlorate (the oxidizing agent as well as a fuel), and iron(III) oxide (the catalyst). These reactants are mixed into a liquid polymer, which sets to a solid inside the rocket shell. A variety of products can form when the mixture is ignited. One of the reactions is... 

Fossil fuels are nonrenewable, and combustion products contaminate the atmosphere. Consequently, scientists are searching for new sources of energy. One possibility is molecular hydrogen, which releases energy when it reacts with oxygen 2 H2(g) + 02(g) 2H2 0(/) + Energy Hydrogen powers the rockets of the space shuttle,... 

Alkaline fuel cells (AFCs). The electrolyte is 40 to 70% KOH, the working temperatures are 60 to 240°C. Such systems were used in the spacecraft of the Apollo program and in the U.S. space shuttle. 

The propellant mixture in each solid rocket booster of the Space Shuttle contains ammonium perchlorate ( the oxidizer, 69.6% by weight), aluminum ( the fuel, 16% by weight), an iron oxide catalyst (0.4% by weight), a polymeric binder that... 

After it has been separated, hydrogen is an unusually clean-energy carrier and clean enough for the U.S. space shuttle program to use hydrogen-powered fuel cells to operate the shuttle s electrical systems while the by-product of drinking water is used by the crew. 

Since liquid hydrogen has the greatest energy content per unit weight of any fuel, NASA used liquid hydrogen as the primary fuel for the Saturn 5 moon rockets and the Space Shuttle. 

The space shuttle uses a fuel cell as a source of energy. This cell depends on the oxidation of hydrogen by oxygen to form water. The fuel cell operates under basic conditions, so it is sometimes referred to as an alkaline fuel cell. Figure 11.31, on the next page, shows the design of the cell. The half-reactions and the overall reaction are as follows. 

---