Space Flyer Unit Research Articles

Bio Experiment on Space Flyer Unit: Effects of Gravity on Early Development of Japanese Red Bellied Newt

Bio Experiment on Space Flyer Unit: Effects of Gravity on Early Development of Japanese Red Bellied Newt

Influence of space debris impact on solar array under power generation

Recently solar array has become higher in potential and larger in capacitance. Therefore, possibility of collision between space debris and enlarged solar array has been pointed out. Many debris and dust impacts were confirmed on fuselage of the retrieved satellite Space Flyer Unit (SFU) and solar array paddle of satellite Eureca. If space debris collides with the solar array of an orbiting satellite, it may cause generation of high-density plasma by debris impact induced dielectric breakdown of satellite component and the phenomenon called sustained arc. By the short circuits on the solar array, current will not flow into a pay load of the satellite. And the worst event by this discharge is operational end of the satellite. However, any events of discharge phenomenon by debris impact cannot be yet confirmed. But we cannot ignore such possibility of discharge by debris impact. The purpose of this paper is to investigate discharge condition due to debris impact which yields us reduction of electric power of solar array, and to reduce influence of the impact on satellite missions. In this study, a solar array coupon was tested under hypervelocity impact in which a projectile was launched by a two-stage light gas gun installed in Kyushu Institute of Technology (KIT).

Preliminary study on sustained arc due to plasma excited by hypervelocity impact of space debris on the solar array coupon

Recently, solar array has become higher in potential and larger in capacitance. Therefore, possibility of collision between space debris and enlarged solar array has been pointed out. Many debris and dust impacts were confirmed on fuselage of the retrieved satellite space flyer unit (SFU) and solar array paddle of satellite Eureca. If space debris collides with the solar array of an orbiting satellite, it may cause generation of high-density plasma by debris impact-induced dielectric breakdown of satellite component and the phenomenon called discharge. This discharge short circuits the solar array and current will not flow into pay load of the satellite. And the very worst event by this discharge is the operational end of the satellite. However, any events of discharge phenomenon by debris impact cannot be yet confirmed. But we cannot ignore such possibility of discharge by debris impact. The purpose of the present paper is to investigate discharge condition due to debris impact which yields us reduction of electric power of solar array, and to reduce influence of the impact on satellite missions. In this study, a solar array coupon was tested under hypervelocity impact in which a projectile was launched by a two-stage light gas gun installed in Kyushu Institute of Technology (KIT). As a result, we verified discharge event in the hypervelocity impact ground test.

Multi-layered foil capture of micrometeoroids and orbital debris in low Earth orbit

Analyses of multi-layered polymer insulation foils recovered from the Japanese Space Flyer Unit suggest that such foils have the potential to retain substantial remnants of micrometeoroid and space debris material from hypervelocity impact events. A purpose-built multi-layer foil collector could sample large numbers of impacts from smaller particles in low Earth orbit. Abundant residue could be classified as spece debris or micrometeoroid in origin, both quickly and easily – a significant improvement over materials surveyed on an opportunistic basis (such as solar cells, aluminium surfaces and aluminised multi-layer insulation foils) or metallic foil collectors, in that it would allow recognition of the whole range of impacted projectile compositions in a single survey. The collector is also intended to be relatively easy and cheap to construct, light in weight, negligible in power requirements, easy to deploy, of large surface area, easy to retrieve, small in storage, and unlikely to acquire substantial contamination upon the crucial inner foils.

Observations on hypervelocity impact damage sustained by multi-layered insulation foils exposed in low Earth orbit and simulated in the laboratory

Retrieved multi-layered foil thermal blankets exposed on the Japanese Space Flyer Unit and the MIR Space Station have revealed abundant evidence of damage generated by space debris and micrometeoroids. The blankets have acted as an efficient shield by disrupting small particles during penetration through the many foil layers, with abundant impact-derived residue material being identifiable on the upper layers of the blanket. The morphology of the impact-derived residues is complex with projectile fragments bound by degraded foil material, resulting in highly-evolved melt droplets. A light-gas-gun impact test programme was carried out using single homogeneous olivine mineral grains to help understand the observations of residue made on space-exposed samples from MIR and the Japanese Space Flyer Unit. The damage observed on the test samples, and the distribution and nature of the residue material, were found to be very similar to those from surfaces exposed in low Earth orbit. However, one of the experimental impact residues, preserved on the third layer of the foil stack, did yield a well-defined 820cm-1 Raman band, characteristic of olivine. This observation suggests that the particle had retained crystallographic integrity and had not undergone extensive melting and quenching during the shock-heating of the impact events. © 2003 Elsevier Ltd. All rights reserved.

Lessons learned from the space flyer unit (SFU) mission

The Space Flyer Unit (SFU) system and mission chronology are briefly introduced. Lessons learned from the SFU mission are categorized as programmatic and engineering lessons. In the programmatic category are dealt with both international and domestic collaborations. As for the engineering lessons safety design, orbital operation, in-flight anomaly, and post flight analyses are the major topics reviewed.

Space plasma effects on spacecraft surface driven by solar array voltage

Spacecraft potential and associated plasma effects induced by solar array voltage were studied by Space Flyer Unit (SFU), a 4-ton class experimental platform on orbit at a height of 480 km . SFU had two solar array paddles of 52 V . The potential of the SFU main body during the daytime was measured to be more than 40 V negative driven by the solar array voltage. When SFU was negatively biased, plasma perturbations in a frequency range below 100 kHz were observed. In the direction of the sunlight, broadband oscillations extending beyond 1 MHz were also detected.

Accomplishment and prospect of isas electric propulsion

The electric propulsion is one of the promising choices because of its high specific impulse when one would like to give a rise to the limited payload capability of the launch vehicle. Especially in a long-term mission or a high-energy mission, the electric propulsion provides less consumption of propellant or more payload mass under a given mass constraint of the satellite and the scientific probe. The Institute of Space and Astronautical Science (ISAS) has been developing a variety of electric propulsions for 30 years. These continuing efforts are now turning out to be an application era for the propulsion systems for near-Earth and/or interplanetary transportation of space probes with scientific missions in the 21st century. A magnetoplasmadynamic (MPD) arcjet successfully finished its space test onboard the Space Flyer Unit (SFU), a microwave ion engine is being developed for the asteroid sample return mission, and a DC arcjet is ready to be used for future orbit transfer or attitude control of Earth-bound satellites. The electric propulsions are divided into three major groups according to their plasma acceleration principles, electromagnetic, electrostatic and electrothermal devices. In ISAS, all the types of electric propulsions are studied as the high Δ V mission enablers and in this report these accomplishments and future prospects are introduced.

Japanese Red-Bellied Newts in Space - AstroNewt Experiment on Space Shuttle IML-2 and Space Flyer Unit

Biological effects of gravity was examined in embryonic development of Japanese red bellied newt. Two space newt missions were conducted in 1994 and 1995. The Second International Microgravity Laboratory was flown in 1994 as one of the SpaceLab missions. Space Flyer Unit, a Japanese space platform, was delivered to the earth orbit by the third launch of the H-II rocket and retrieved by Space Shuttle in 1996. Female newts were induced to lay eggs in orbit at these two space missions. Eggs were successfully obtained on both missions, and exposed to space environment from its early developmental stages. Morphology of the embryos was found not deviated from those developed on ground, as long as in the images taken in orbit or the examined specimen retrieved to ground. On the other hand, pathological changes were discovered in several organs of the adult newts that returned alive from their space flight.

Japanese contribution to in-situ meteoroid and debris measurement in the near Earth space

This paper reviews major results of present studies and recent developments for future missions in the Japanese space program regarding in-situ measurement and collection of micrometeoroids and orbital debris in the near Earth space. Japan’s contribution in this area began with the post flight impact analysis of the Space Flyer Unit (SFU) satellite which was returned to Earth in 1996 after 10-month exposure in space. Despite a decade later than similar efforts first conducted in the USA and Europe, it resulted in a record of over 700 hypervelocity impact signatures, which now forms the nation’s first database of real space impacts being open to public in the Internet. Together with laboratory impact tests, both morphological and elemental analyses of the impact craters yielded new insights of the meteoroid to debris ratio as well as flux variation compared with the previous spacecraft. The next step was a passive aerogel exposure in the STS-85 shuttle mission in 1997. No hypervelocity impact was found there but its experience has been incorporated for designing a microparticle collector to be on-board the Japan Experiment Module-Exposed Facility of the International Space Station. All of such “passive” collection of micro-impact features, however, still leave the significant uncertainty in the quest of their origins. Therefore an aerogel-based “hybrid” dust collector and detector (HD-CAD) is currently under the development. It measures time of impact and deduces impactors’ orbital and physical parameters by detecting impact flash while still capturing them intact. The system is suitable for both (1) sample return missions in LEO as well as to parent bodies of meteoroids, i.e., comets and asteroids, and (2) one-way mission to where the thermal and plasma environment is such that impact induced plasma detectors may suffer from significant noise, e.g., a Mercury orbiter and a solar probe. Together with unambiguous dust samples from a comet by STARDUST and an asteroid by MUSES-C as references, the HD-CAD in the LEO will be able to deduce the accretion rates of the cometary and asteroidal dust grains on the Earth.

Plasma effects driven by electromotive force of spacecraft solar array

SFU(Space Flyer Unit), a 4‐ton class experimental platform, was on orbit at the height of 480 km circular for 10 months from 1995 to 1996. It carried environment diagnostic packages which contained plasma probes and wave receivers to study the plasma environment surrounding the SFU. The potential of the SFU main body during the daytime reached about 40 V negative with respect to the ambient plasma, which was driven by the electromotive force of the SFU solar array paddles(52 V). It was found that the negative potential resulted in the formation of ion flow towards the SFU main body with fluctuations in a frequency range below 100 kHz. In the sunlight, the wave receiver detected broadband fluctuations extending beyond 1 MHz. This study provides the first observation on the plasma effects of spacecraft potential biased by the solar array voltage.

Post-flight analysis of the SFU: Current status and future plan

The Space Flyer Unit (SFU) has provided investigators in Japan with our first opportunity to conduct an extensive post-flight analysis (PFA) of particulate impacts on a retrieved satellite, and thereby further our goals in space debris research (Kibe et al., 1997). The PFA has now been in progress for some time, and in this paper the present status of our investigations is reported, our findings to date are briefly summarised, and finally a plan for the immediate future is outlined.

A diagnostic study of plasma CVD under microgravity and its application to diamond deposition

Abstract Diamond thin-film was synthesized under microgravity using Japanese free-flyer (SFU, Space Flyer Unit) launched in March 1995. This program achieved the space-based production of diamond by Chemical Vapor Deposition (CVD). The DC plasma excitation method was applied to hydrogen-methane mixed gas within the pressure range of 2.66∼6.55 × 10 3 Pa. Remarkable differences of the electron temperature of hydrogen plasma were confirmed between the microgravity and the on-ground experiments. The intensity ratio of CH/H α measured by emission spectroscopy was found as a sensitve indicator of gravity effects on gaseous chemistry and diamond quality.

Real-Time Orbit Determination Onboard SFU (Space Flyer Unit) Using GPS Data

The Space flyer unit (SFU) is an unmanned, retrievable and reusable multipurpose space platform. It was launched by the Japanese H-II launch vehicle in March 1995 and was retrieved by the United State's Space Shuttle STS-72. We tried realtime orbit determination for the SFU using Global Positioning System.(GPS), and the experiment was very successful. In addition to the free-flight, we were able to evaluate continuous real-time OD solution during orbital maneuvers and attitude control. The real-time orbit solutions from the experimental GPS receiver onboard the SFU are evaluated in view of their accuracy and reliability for use in SFU orbit determination.

電気推進の現状と展望 ＳＦＵ（Ｓｐａｃｅ Ｆｌｙｅｒ Ｕｎｉｔ）のＥＰＥＸ（Ｅｌｅｃｔｒｉｃ Ｐｒｏｐｕｌｓｉｏｎ Ｅｘｐｅｒｉｍｅｎｔ）実験

電気推進の現状と展望 ＳＦＵ（Ｓｐａｃｅ Ｆｌｙｅｒ Ｕｎｉｔ）のＥＰＥＸ（Ｅｌｅｃｔｒｉｃ Ｐｒｏｐｕｌｓｉｏｎ Ｅｘｐｅｒｉｍｅｎｔ）実験

Satellite Technology in Space Age. Flight Operation Technique of Space Flyer Unit.

Satellite Technology in Space Age. Flight Operation Technique of Space Flyer Unit.

The first results of meteoroid and debris impact analyses on Space Flyer Unit

The Space Flyer Unit (SFU) was retrieved from space after its 10-month mission in January 1996. Here we report the first findings from the post flight analysis of its Kapton MLI and Teflon radiators in terms of impact flux, crater morphology and implications of impactors' origins. The impact flux on the Sun face is also compared with the LDEF, EuReCa and HST data. On the Kapton MLI, some directional information can be deduced and its capture cell structure promises a high survivability of residues for chemical analysis. The peripheral flux variation is not inconsistent with the EuReCa data favouring for the Earth's apex. The anti-Sun face flux exceeded the Sun face by a factor of 1.7. The size distribution index of the impact features on the Sun face Teflon agreed with the certain size ranges of the previous spacecraft. Plans of forthcoming studies such as detailed CCD/laser scanning, calibration impact experiments and chemical analysis are also addressed.

ＳＦＵ（Ｓｐａｃｅ Ｆｌｙｅｒ Ｕｎｉｔ）プロジェクト概要

ＳＦＵ（Ｓｐａｃｅ Ｆｌｙｅｒ Ｕｎｉｔ）プロジェクト概要

On-orbit thermal behaviour of the IRTS cryogenic system

The IRTS (Infrared Telescope in Space) was launched at 08:01 on 18 March 1995 UT by the H-II rocket as a part of the Space Flyer Unit (SFU), which is a re-usable free flyer designed as a multi-purpose common facility for scientific and engineering experiments. The He II tank was estimated to be approximately 85% full at 1.84 K at the moment of launch, 11 h after pumping was disconnected and the tank was sealed. The vapour evacuation through a porous plug was resumed 28 min after the launch. The thermal state reached the anticipated steady state at 1.91 K on the third day without any anomalous thermal behaviour of the porous plug in the initial zero- g state. Over the course of 10 days the SFU transferred to a low earth orbit (LEO) at 486 km from the initial phase orbit at 340 km with the telescope aperture lid ejecting on day 11 after launch. A 3He refrigerator was then activated to decrease the temperature of some bolometer detectors down to 302 mK for observations in the far IR region. Every detector worked quite satisfactorily. The stable thermal state of He II at 1.91 K was maintained until the depletion of He II at 09:30 on 24 April UT. The cold life is found to be fairly close to the prediction on the basis of the ground test data. On April 27 the sun shield was jettisoned for the safe retrieval by a US shuttle in January 1996, and the IRTS mission was completed because of the regular shift of the SFU mission time-line to another experiment. In this report the flight data of the thermal performance of the cryogenic system are discussed.

The IRTS (Infrared Telescope in Space) Mission

The Japanese satellite-borne infrared telescope, the Infrared Telescope in Space (IRTS), has completed a successful survey of a portion of the infrared sky. The IRTS consists of a 15 cm telescope cooled with superfluid liquid helium, and is installed on board the Space Flyer Unit (SFU) spacecraft. The SFU was launched on 1995 March 18 UT. The sky survey by the IRTS started on March 29 UT, and was completed on April 25 UT after exhausting its liquid helium. The cryogenic system operated as designed, and maintained the telescope and the focal-plane instruments at a stable temperature of 1.9 K for 38 days. The four focal-plane instruments, which together covered almost the entire infrared wavelength range, observed a sky area of about 2700 deg2 and returned a wealth of new data on a variety of objects, including the zodiacal light, interstellar gas and dust, near-infrared cosmic background light and point sources.