Residual Propellant Research Articles

The recent fragmentations of LEO upper stages

Between March 1991, and March 1993, three USSR/CIS upper stages from two different launch vehicle families broke up at moderate LEO altitudes, creating more than 300 long-lived debris. All three vehicles had successfully completed their satellite delivery missions before the breakups occurred 1–21 days after launch. Two of the vehicles, a Kosmos second stage and a Zenit second stage, apparently experienced multiple fragmentations. Joint Russian-American accident investigations have characterized the fragmentation events, uncovered potential accident scenarios, and recommended corrective measures for future missions. As seen repeatedly in recent years, residual propellants continue to be an apparent source for launch vehicle breakups. International cooperation can not only assist in better defining the near-Earth space environment, but also can improve space operations and mitigate the unnecessary growth of the Earth's satellite population.

Development of protective layers on high-temperature alloys against hydrogen permeation

For TEXTOR a multiple pellet injector system is in preparation which consists of a) nine freezing cells for the pellet formation accommodated in a common cryostat and nine gas guns being built at CEA, Service des Basses Temperatures in Grenoble, b) a system for the propellant-gas handling together with the pellet diagnostics being built at KFA Julich. The pellets have a cylindrical shape with a size of 1.3 mm in diameter and a length of 1.5 mm. The guns are operated with a propellant gas pressure of up to 200 bar and the pellets are accelerated up to velocities of 1.4 km/s. The propellant gas valve of each gun is optimized to release as little gas as possible; nevertheless the gas release amounts to 0.3 bar·l. This amount of gas (typically hydrogen) has a mass more than a factor of hundred larger than that of one pellet, but only an amount of one percent of the pellet mass can be tolerated. The conventional way of handling the propellant gas is either to feed the pellets through a capillary guiding tube or by using two or three differential pumping chambers. The first scheme may cause pellet ruptures at velocities higher than 1 km/s and the second one requires large expansion volumes and strong pumping. In the TEXTOR pellet injector we are using a combination of a muzzle brake, three small expansion volumes and two fast closing valves for each gun. The muzzle brake diffuses the stream of the propellant gas immediately after the end of the barrel. Most of the gas is directed into two expansion chambers which have volumes of only 0.5 l each. Within 1 ms after the passage of the pellet, a newly developed valve closes the first two expansion volumes from TEXTOR, thus reducing the residual propellant gas to less than 0.5 mbar·l. A second combination of an expansion volume of 1 l and a fast valve reduces the propellant gas further down to about 10−2 mbar·l, which is less than 1 % of the pellet mass (typically 4 mbar·l). Three IR-light barriers are integrated in each pellet path; their photodiodes provide signals for the pellet speed determination and trigger signals for the fast closing valves. They also give the open/closed status of the valves. The mass of the individual pellet is measured by a microwave system consisting of a μW-cavity, a wave guide, a gunnplexer oscillator and a detection circuit operating at a frequency of 10.3 GHz.

Analysis of the orbit of 1965-11D (COSMOS 54 rocket)

The satellite 1965-11D was the final-stage rocket used to launch Cosmos 54, 55 and 56 into orbit on 21 February 1965. The orbit of 1965-11D was inclined at 56° to the Equator, with an initial perigee height of 280 km; the lifetime was nearly 5 yr, with decay on 23 December 1969. The orbit has been determined at 75 epochs during the life, using the RAE orbit determination program PROP with over 4000 observations, photographic, visual and radar. Observations from the Hewitt camera at Malvern were available for 34 of the 75 orbits and typical accuracies for these orbits are 0.0005° in inclination and 100 m in perigee height. The variations in perigee height have been analyzed to determine reliable values of density scale height, at heights between 240 and 360 km. The analysis also revealed a rapid decrease of 5 km in perigee distance early in 1966, attributed to the escape of residual propellants. The variations in orbital inclination have been analyzed to determine upper-atmosphere zonal winds and 15th-order harmonics in the geopotential. The region of the upper atmosphere traversed by 1965-11D near its perigee is found to have had an average rotation rate of 1.10 ± 0.05 rev/day in 1966–1967, and 1.00 ± 0.03 rev/day between March 1968 and May 1969. In late 1969 there were probably wide variations in zonal winds, with east-to-west winds of order 100 m/s followed by west-to-east winds of order 200 m/s. The changes in inclination at the 15th-order resonance in July 1969 have been analyzed to give the first accurate values of lumped 15th-order harmonics obtained from a high-drag satellite. This success points the way towards similar analyses of the many other high-drag satellites that pass through 15th-order resonance, to evaluate individual geopotential coefficients of order 15 and even degree.

Ignition transients in small hypergolic rockets.

Factors influencing rocket ignition pressures and conditions leading to large ignition overpressures, estimating residual propellant in rocket combustor

Optimum selection of fuel bias for maximizing the range and for minimizing the residual propellant of the Thor, Atlas and Titan missiles

The distributions of residual propellant (outage) and of range are obtained as functions of the basic missile parameters and of fuel bias for one, one and one half, and two stage ballistic missiles flown to maximum range without a propellant utilization system. Fuel bias, the excess of fuel loaded above nominal, is selected to maximize the probability that residual propellant does not exceed a specified value, or that range exceeds a specified distance.