Oscillatory Thermocapillary Flows in Simulated Floating-zones with Time-dependent Temperature Boundary Conditions

This study deals with numerical simulations of the Maxus sounding rocket experiment on oscillatory Marangoni convection in liquid bridges. The problem is investigated through direct numerical solution of the non-linear, time-dependent, three-dimensional Navier–Stokes equations. In particular, a liquid bridge of silicon oil 2[cs] with a length L=20 [mm] and a diameter D=20 (mm) is considered. A temperature difference ΔT=30 [K] is imposed between the supporting disks, by heating the top disk and cooling the bottom one with different rates of ramping. The results show that the oscillatory flow starts as an ‘axially running wave', but after a transient time the instability is described by the dynamic model of a ‘standing wave', with an azimuthal spatial distribution corresponding to m=1 (where m is the critical wave number). After the transition, the disturbances become larger and the azimuthal velocity plays a more important role and the oscillatory field is characterized by a travelling wave. The characteristic times for the onset of the different flow regimes are computed for different rates of ramping.     

Sources and Losses of Energetic Electrons at Low Altitudes from Satellite Data

Fluxes and differential spectra of 0.04–2.0 MeV electrons at low altitudes in the Earth's magnetosphere are considered in comparison with the model spectra AE-8 MAX and AE-8 MIN. Possible causes of the discrepancy between the observational and model spectra are discussed. The coefficients of radial diffusion at various L-shells are estimated for the maximum of solar activity (using the Interkosmos-19 data) and for the minimum of solar activity (using the Kosmos-1686 data) and are derived from the model AE-8. A quantitative evaluation of the electron yield from radial diffusion at low L shells is derived. Ionization losses, Coulomb angle scattering, and resonant wave–particle interaction are considered as the loss mechanisms. A calculation of these losses at the low L-shells is given. The electron distribution at low L-shells is best fitted by a combination of dissipative terms from different models: Coulomb scattering dominates at the lower L-shells (L = 1.2–1.4) and the resonant wave–particle interaction controls the radiation belt maximum and the gap (L = 1.4–2.0).     

State of the art, lightweight scientific experiments available for small to micro satellite missions

A selection of light weight scientific instruments originally designed for major international missions but which, because of their modest resource requirements, can now in addition be flown aboard ‘small’ to ‘micro’ satellites are, briefly, described. These instruments have the capability to either make measurements of constituents of the Earth's energetic particle environment, or provide detailed monitoring of multiple parameters of the cold terrestrial ionospheric plasma. Scientific reasons for flying such instruments in LEO are, in each case, advanced. Individually, they constitute representative examples of a mature genre of commercially available (a cost parameter of £100k/kg can be achieved), light weight, space qualified, instruments which can contribute significantly to the implementation of first class scientific programs aboard small/micro satellites. Uniquely fault tolerant data processing units are a feature of these devices.     

The astronaut and the robot : Short- and long-term scenarios for space technology

A series of major accidents - the explosion of the Space Shuttle Challenger, the destruction of Titan and Delta launchers, and failures of the Ariane rocket series - has led to a reexamination of Western space programmes. In the short term, all satellite launches have been delayed. This is not an insurmountable obstacle, although it will inevitably delay the first space-based tests of SDI hardware. The author outlines the growing gap between the immediate needs of organizations which launch satellites and the more uncertain ambitions of the ‘conquerors’ of space. The former are now bearing the costs of the latter, who are aiming at manned space flights and a human presence in space. In the longer term, these objectives have justifications other than simple industrial and commercial logic. The author suggests that an attempt should be made to reconcile immediate military and industrial needs with the human desire to overcome the ‘Icarus complex’ in the long-term future.     

Moscow declaration

This declaration was made at the International Conference on Aerospace Complex Conversion, organized by the United Nations in Moscow, 12–16 October 1992. It provides a follow-on to the UN conference on ‘Conversion - opporunities for development and environment’ held in Dortmund, Germany, 24–27 February 1992, and reported in the August 1992 issue of Space Policy by Professor K.H. Böckstiegel, who chaired the Plenary Session in Moscow.     

Orbiting solar telescope on “Salyut-4” station

The orbiting solar telescope on Salyut-4 (F = 2,5 m, d = 250 mm) produces images of the Sun on the entrance slit of a stigmatic two-grating spectrograph (R₁ = 1 m, N₁ = 1200 lines/mm; R₂ = 0.5 m, N₂ = 2400 lines/mm, dispersion 16 Å/mm, spectral resolution 0,3 Å). The automatic system keeps the observed solar features on the slit of the spectrograph with an accuracy of 3–4 arc sec. The far UV-spectra (970–1400 Å) of solar flares, brightenings, flocculi and prominences were photographed and fresh coatings of mirrors were made during the flight.     

Shaping a legal framework for the commercial use of outer space: recommendations and conclusions from Project 2001

Private and commercial activity in outer space still poses challenges to space law and policy. Within ‘Project 2001’—a legal research project by the University of Cologne's Institute of Air and Space Law and the German Aerospace Center (DLR)—six international expert working groups examined international and national laws, in order to identify gaps and, where necessary, propose improvements to the present legal framework for private space activities. The results were presented and discussed at an international colloquium in May 2001 in Cologne, Germany, where final conclusions have been drawn. This report presents a summary of the project's work and main conclusions, which are documented in full in a comprehensive book to be published in May 2002.     

Pricing competitively — a response to Jay Lightfoot

A recent paper in this journal criticized the two methods commonly used to allocate the costs of multi-payload launches, and proposed two new alternatives. The paper argued that ‘Shapley-value’ pricing and the ‘Independent Cost Proportional Scheme’ are immune to instability problems possible under the traditional mass-proportional approach, and reduce ‘subsidies’ paid to small payloads. This rejoinder shows that neither claim is true in general. It also questions whether new pricing formulas are truly needed — or even sustainable in today's competitive market.     

BNSC/RAS Town Meeting

In London on 20 September, the British National Space Centre and the Royal Astronomical Society convened a ‘Town Meeting’, a usage picked up from NASA. Basically it was a debate without the competetive element, whose topic was the next two of the European Space Agency's four ‘Cornestone’ projects for the ‘Horizon 2000’ programme, total budget 584 million ECU (about £467 million). The question in September was which would be no. 3 and which no. 4. Duncan Lunan reports on the discussion and the choices made.     

Star wars brought to earth

This article considers the thinking behind, and the ramifications of, President Reagan's Star Wars ‘vision’. The author argues that the Strategic Defense Initiative (SDI) is incompatible with other aspects of the Reagan administration's own defence policies and that the ‘security shield’ version of it would make future US-Soviet arms agreements impossible. Only the so-called ‘prudent hedge’ research looks viable in the longer term. The SDI's main value will have been in bringing the USSR back to the negotiating table.     

Improved space safety for astronauts

The 2003 Columbia accident demonstrated that spaceflight remains a risky and dangerous human endeavor, yet there have been few ‘unofficial’ investigations into astronaut safety. This report summarizes the findings of one such study by George Washington University's Space & Advanced Communications Research Institute—e.g. that simplicity of design may be better than complexity, that cargo missions would be better carried out robotically and that all new space transportation systems should be developed to common international standards—before examining ways that international cooperation can advance the cause of space safety. In establishing future space safety standards input from a wider range of participants (industry, universities and private research institutes, as well as space agencies, etc.) will need to be sought.     

The military in space : A historical relationship

The Deputy Chairman of the US Joint Chiefs of Staff offers some observations on the ‘militarization’ of space, arguing that military involvement does not necessarily mean an environment will become ‘weaponized’. He also comments on some future US space activities.     

Worldwide direct audio broadcasting from space : Promoting ‘Glasnost’ with DBS-A

About 100 countries now pursue their ‘public diplomacy’ interests by broadcasting audio programmes via shortwave to 400 000 000 radio listeners. However signals broadcast by surface-based shortwave transmitters are limited in coverage, reliability and quality, and shortwave broadcasting suffers from increasingly difficult operating and political problems. Space technology could now begin to be employed to create common-carrier, common-user (Intelsat- and Inmarsat-like) space-based systems which could provide a truly excellent, low-cost, direct-broadcast audio service throughout the world. The world's governments could thereby use space in a new way to promote ‘Glasnost-Openness’ for ‘the benefit of all mankind’.     

X-38, CRV and CRV Evolution Program Overview and European Role

The X-38 Project forms part of the “X” prototype vehicle family developed by the United States. Its development was initiated by NASA to prepare the Crew Return Vehicle (CRV). The European participation in the X-38 Program has been significantly extended since the start of the X-38 cooperation in 1997 and is realized by ESA's “Applied Reentry Technology Program” and the German/DLR “Technologies for Future Space Transportation Systems” (TETRA) Project. European contributions to the X-38 Vehicle 201, (V-201) can be found in all technical key areas. The orbital flight and reentry with the X-38 V-201 will conclude the X-38 project in 2002.The CRV will be used from about mid-2005 as ’ambulance‘, ’lifeboat‘ or as alternate return vehicle for the crew of the International Space Station. Recognizing the very productive and mutually beneficial cooperation established on X-38, NASA and ESA have decided to continue this cooperation into the development of the operational CRV. The Phase C/D will be completed shortly after the Critical Design Review, scheduled for August 2002. The CRV production phase will start in October 2002 and will cover production of four CRV vehicles, ending in 2006.Based on the objective to identify a further evolution potential of the CRV towards a Crew Cargo Transfer Vehicle (CCTV), NASA has implemented upgrade studies in the CRV Phase C/D.     

Surface temperature distribution along a thin liquid layer due to thermocapillary convection

The surface temperature distributions due to thermocapillary convections in a thin liquid layer with heat fluxes imposed on the free surface are investigated. The nondimensional analysis predicts that, when convection is important, the characteristic length scale in the flow direction L, and the characteristic temperature difference ΔT₀, can be represented by and , respectively, where L_R and ΔT_T are the reference scales used in the conduction-dominant situations with A denoting the aspect ratio and Ma the Marangoni number. Having had L and ΔT₀ defined, the global surface-temperature gradient ( ), the global thermocapillary driving-force, and other interesting features can then be readily determined. Finally, numerical calculations involving a Gaussian heat flux distribution are presented to justify these two relations.     

A management approach for allocating instrument development resources

The Cassini Science Management Plan was developed for NASA's Cassini mission to Saturn to assist the Science Instrument Manager in guiding the development of the spacecraft's science payload. This plan, unlike previous development approaches, allocated the entire mass, power, data rate and budget resources for the science instruments to the Principal Investigators. The result removed the Cassini Project from adjudicating and reallocating resources for instrument development problems. Instrument development problems that did occur were resolved by the Principal Investigators themselves through the use of a ‘resource exchange’. The exchange allowed Principal Investigators to submit ‘bids’ (i.e. a request for resources) to a database. Principal Investigators were allowed to barter their own resources with other investigators. The resulting exchange or multilateral trade allowed the investigators to reallocate their resource to ‘better’ their current position.     

A new paradigm for international cooperation in space exploration

In announcing a new Vision for the US space program, President George Bush committed the USA to “a long-term human and robotic program to explore the solar system”, via a return to the Moon, leading to exploration of Mars and other destinations. He also stated that other nations would be invited to join the vision. Many other nations have, or are developing, ‘exploration visions’ of their own. The potential for international cooperation therefore exists, both at the vision and program/project levels. This paper, based on Working Group discussions as part of an AIAA space cooperation workshop,¹ presents an approach for maximizing the return on all global investments in space exploration. It proposes an international coordination mechanism through which all these various national activities could be integrated into an inherently global enterprise for space exploration, a ‘virtual program of programs’. Within the context of the coordination, individual activities would utilize the full range of cooperative mechanisms for implementation. A significant benefit of this mode of conducting cooperation is that it would not require the negotiation of complex overarching international agreements as a precondition for initiating international activity.     

It''s all a matter of fact. After all, fact matters

The fourth annual ‘British Rocketry Oral History Project’ (BROHP) conference was held from 2 to 4 April 2002, again in the magnificent grounds of Charterhouse School in Surrey. The conference marked a new point in its brief history, enlarged in scope and depth to extend to a new audience; yet one point remained constant throughout, namely that ‘history matters’. This report discusses the themes of the 2002 conference.     

Science in the national vision for space exploration: objectives and constituencies of the ‘discovery-driven’ paradigm

The NASA/White House Vision for Space Exploration is primarily focused on the development of human and robotic systems that will enable ‘discovery-driven’ investigations in areas important to the scientific community: Mars, the solar system's outer moons, and planets orbiting other stars. Such a portfolio can only be realized if NASA is prepared to target investment at opportunities that are most scientifically compelling. NASA's leaders will have to make decisions in subjective and uncertain environments about the relative long-term value of different kinds of scientific discoveries seen as equally important to different groups. A management paradigm of this kind will imply assessment of heterogeneous priorities and management of interdependent and changing requirements. In order to identify the basis and implications of a ‘discovery-driven’ paradigm, this paper surveys the relationship between the Vision's principles and its programmatic content, the objectives of the Vision's scientific focus areas and their interrelationships, and the public context in which science-focused exploration will proceed.