China's Tiangong-1 space lab to fall to Earth between October 2017 and April 2018
A rendering of the Tiangong-1 space lab in orbit. (Photo: CMSA)
China has released an update on the fate of its orbiting Tiangong-1 space lab, which in March 2016 was revealed to be no longer functioning and would be making an uncontrolled reentry into the Earth's atmosphere.
According to a note verbale from the Permanent Mission of China to the United Nations (Vienna), Tiangong-1's average orbital altitude is 349 kilometres, decaying at a daily rate of approximately 160 metres. Its re-entry into the Earth’s atmosphere is expected to occur between October 2017 and April 2018.
The unsigned diplomatic note (pdf) addressed to Secretary-General provided the update on the re-entry of the 8 metric tonne Tiangong-1 space lab, whose name means 'heavenly palace', on May 10.
In September Wu Ping, deputy director of the China Manned Space Agency (CMSA), stated that Tiangong-1 was orbiting at an altitude of 370 km and declining by 110 metres per day, with reentry expected in the latter half of 2017.
Space station stepping stone
The 10m long, 3.35m wide Tiangong-1 space lab was launched in September 2011 as a stepping stone on the way to a large modular Chinese space station, with the Tianhe core modulelooking set for launch in early 2019.
Crucially, Tiangong-1 demonstrated rendezvous and docking technologies, completing the procedures six times with the uncrewed Shenzhou-8 and crewed Shenzhou-9 and Shenzhou-10 spacecraft between 2011 and 2013.
Above: Shenzhou-10 docking with Tiangong-1 in June 2013.
Tiangong-1 hosted two three-person crews, including China's first woman in space, Liu Yang, in June 2012, and facilitated a live space lecture by Wang Yaping to millions of school children in June 2013, while providing tests of life support systems.
The communication went on to state that China would act to enhance its tracking and monitoring of Tiangong-1’s orbit and publish timely forecasts of its re-entry.
The China Manned Space Agency will also be providing information on Tiangong-1’s orbital status in real time through its website, in both Chinese and English.
Atmospheric drag - caused by collisions between the spacecraft and molecules - is responsible for the decay of the orbit Tiangong-1, as with other satellites in low Earth orbit.
The Earth's atmosphere is also likely to see to it that most of the spacecraft is not a threat to the surface.
Above: Wang Yaping delivers a lecture on physics in microgravity.
"According to calculations and analyses, most of the structural components of Tiangong-1 will burn up and be destroyed during the course of the re-entry. The probability of harm to aviation and on the ground as a result of Tiangong-1’s re-entry is very low," the note reads.
An Universe Today article - in constrast to many sensationalist reports - states that the likelihood of any one person being struck by a piece of space debris is 1-in-3,200, citing a NASA scientist discussing the upcoming reentry of the 6-ton UARS satellite in 2011.
Space junk regularly reenters the atmosphere, sometimes providing a surprise show for onlookers, as with the second stage of China's first launch of a Long March 7 rocket last year.
Conversely Russia's Mir space station was deorbited through a controlled reentry over the South Pacific in 2001.
China says it will announce the final re-entry time and the area likely to be affected well in advance and will issue the relevant information and early warnings in a timely manner, bringing information to the attention of the Secretary-General of the United Nations and the Office for Outer Space Affairs (UNOOSA) through diplomatic channels and to the public through news agencies.
NanoRacks CubeSat Deployer Mission 11 Status Update: Good Deploy!
NanoRacks began the first of two airlock cycles for the 11th and 12th NanoRacks CubeSat Deployer Missions (NRCSD-11, NRCSD-12) on May 16, 2017. We are pleased to update our customers, friends, and shareholders that the first round of deployments has been completed successfully.
NRCSD-11 and NRSD-12 were brought to the International Space Station on the Orbital ATK-7 mission, which launched on April 18, 2017 from the Kennedy Space Center in Cape Canaveral, Florida. This launch was our largest CubeSat mission to date, bringing 34 satellites into the Space Station, plus four CubeSats mounted on externally on the Cygnus spacecraft.
This week, our operations team worked with NASA Johnson Space Station, JAXA, and Astronauts Peggy Whitson and Jack Fisher on the installation of the NRCSD in preparations for the first deployment early morning on May 16th.
Below we share information about the 17 CubeSats deployed this past week as we at NanoRacks gear up for the second airlock cycle scheduled to begin on May 22, 2017, where we will deploy the NRCSD-12 satellites.
In this first cycle alone, the CubeSats deployed represent 10 different countries around the world.
To date, NanoRacks has deployed 154 CubeSats via the NanoRacks CubeSat Deployer on the International Space Station, and 165 CubeSats in total. We continue to show the unique value of using space stations for satellite deployments and appreciate everyone’s continued support.
Congratulations to all of the CubeSat teams, and good luck in your satellite operations!
-The NanoRacks Team
The QB50 Mission consists of dozens of universities located around the world – including Israel, Canada, Australia, Korea, Spain, Germany, France and more. Coordinated by the von Karman Institute and sponsored by the European Commission, the QB50 CubeSats will take advantage of the space station orbit to study the lower thermosphere (200-380 kilometers) collecting scientific climate data, in what is considered by experts a relatively unexplored part of Earth’s atmosphere. The ISS portion of the QB50 Mission involves over 300 students and 50 professionals, which brings the program together.
The QB50 CubeSats deployed in this first airlock cycle:
SOMP2 – TU Dresden, Germany HAVELSAT – Havelsan, Turkey Columbia – University of Michigan, USA PHOENIX – National Cheng Kung University, Taiwan X-CubeSat – Ècole Polytechnique, France QBEE – Open Cosmos Ltd. & University of Lulea, Sweden ZA-AEROSAT – Stellenbosch Univesrity, South Africa LINK – Korea Advanced Institute of Science and Technology, South Korea UPSat – University of Patras and Libre Space Foundation, Greece SpaceCube – Ècole des Mines Paristech, France Hoopoe – Herzliya Science Center, Israel
ALTAIR – Millennium Space Systems
Millennium Space Systems’ NanoRacks-ALTAIR™ Pathfinder spacecraft establishes flight heritage for the majority of the ALTAIR Core product line spacecraft design and for payload support technologies. ALTAIR is the next generation affordable resilient space platform for low-Earth orbit (LEO), Geosynchronous Earth Orbit (GEO) and deep space missions. The key ALTAIR Core hardware designs are demonstrated and flown in their objective design configurations to retire technical risks, increase Technology Readiness Levels (TRLs) and gain flight heritage for future Department of Defense (DoD) and NASA space programs.
SHARC – Air Force Research Laboratory
The Air Force Research Laboratory’s SHARC CubeSat will demonstrate the capability for a CubeSat to perform critical calibration of over 120 Tri-Service C-Bad radars. These calibrations are needed to meet tracking requirements of orbital objects. This CubeSat demonstrates two technologies developed at AFRL/RV under the SBIR program: MMA HaWK deployable solar array and the BCT XACT ADCS System.
SG-Sat – University of Kentucky
The University of Kentucky’s SG-SAT (Stellar Gyroscope Satellite) captures images of star fields to orient a small satellite and test new software that predicts the satellite’s path as it experiences atmospheric drag. This CubeSat was developed from the work of students in the University of Kentucky College of Engineering Space Systems Lab under a Cooperative Agreement between NASA KY, NASA EPSCoR and the NASA International Space Station Research Program. This will be the third cubesat developed for launch by UK Engineering Space Systems
The SGSat project is supported by NASA EPSCoR (Established Program to Stimulate Competitive Research), a program through the NASA Office of Education that develops U.S. aerospace research and the aerospace STEM (science, technology, engineering and math) workforce. The project is administered by NASA Kentucky, hosted at UK to advance aerospace research and education across Kentucky. PI: Dr. James Lumpp, Professor, University of Kentucky College of Engineering
NASA ELaNa XVII Sponsored CubeSats
The following CubeSat missions were selected through the CubeSat Launch Initiative (CSLI) as part of the seventeenth installment of the Educational Launch of Nanosatellites (ELaNa) missions.
Over the past three years, more than 100 students have been involved in the design, development and construction of these CubeSats that will be deployed from the space station via the commercially-developed NanoRacks CubeSat Deployer program.
CXBN-2 – Morehead State University
The Cosmic X-Ray Background NanoSat-2 (CXBN-2) CubeSat Mission developed by Morehead State University and its partners the Keldysh Institute (Moscow, Russia), the Maysville Community and Technical College (Morehead, KY) and KYSpace LLC (Lexington, KY) will increase the precision of measurements of the Cosmic X-Ray Background in the 30-50 keV range to a precision of <5%, thereby constraining models that attempt to explain the relative contribution of proposed sources lending insight into the underlying physics of the early universe. The mission addresses a fundamental science question that is central to our understanding of the structure, origin, and evolution of the universe by potentially lending insight into both the high-energy background radiation and into the evolution of primordial galaxies.
IceCube – NASA Goddard Spaceflight Center
IceCube’s mission is to demonstrate the technology of a sub-millimeter-wave radiometer for future cloud ice sensing. This technology will enable cloud ice measurements to be taken in the intermediate altitudes (5 km – 15 km), where no measurements currently exist. It will perform first-of-a-kind measurements of ice particles embedded within clouds. These measurements will advance atmospheric monitoring technology and also fill in critical gaps in understanding how cloud ice affects the weather and how cloud formations process atmospheric radiation.
CSUNSat1 – California State University Northridge, NASA JPL
The primary mission of CSUNSat1 is to space test an innovative low temperature-capable energy storage system, developed by JPL, raising its TRL level to 7 from 4 to 5. The success of this energy storage system will enable future missions, especially those in deep space to do more science while requiring less energy, mass and volume. This CubeSat was designed, built, programmed, and tested by a team of over 70 engineering and computer science students at California State University (CSUN). The primary source of funding for CSUNSat1 is NASA’s Small Spacecraft Technology Partnership program. For more information see http://www.csun.edu/cubesat.
An illustration of the Mars Base Camp mothership in orbit around the red planet.Lockheed Martin
First, a four- to six-person crew would safely enter orbit around Mars inside the Mars Base Camp mothership.
Next, two or three of the astronauts would board an excursion vehicle tipped with an Orion capsule, which would rocket away from the mothership and toward a moon of Mars.
"The gravity is pretty weird around these things, so you have to keep your distance," Cichan says of Phobos and Deimos.
A Spider Flyer suit attached to an Orion space capsule.Lockheed Martin
After the excursion vehicle pulls up, an astronaut would don a standard extravehicular spacesuit and exit the capsule through an airlock. She would then climb around to the Spider Flyer-Walker, strap in, and detach from the capsule.
The Spider Flyer would have small thrusters in it, so the astronaut could then propel toward the moon all on her own.
The suit's eight legs would splay out ahead of a soft landing:
Once on the surface, the suit's thrusters would fire continuously and gently to press the spider legs into the loose soil below. This would pin the Spider Flyer to the moon while allowing an astronaut to move her arms and legs.
"We can also articulate those spider legs. We can even do a little bit of walking or hopping along the surface," Cichan says, adding that the astronaut could bend over to scoop up soil samples along the way.
Once her science mission is complete, the astronaut would zoom back toward the excursion vehicle with bags of Martian moon grit.
Supplies might also be piloted to the surface of a Martian moon using an uncrewed Spider Flyer.Lockheed Martin
Will NASA buy it?
The idea isn't as out there as it might seem, since Lockheed has a solid track record when it comes to rocket-powered spacesuits.
For example, the company designed and built the Manned Maneuvering Unit (MMU). The device was used by astronauts during three space shuttle missions in the 1980s.
Astronaut Bruce McCandless uses an MMU to fly 320 feet away from the Challenger space shuttle on Feb. 12, 1984.NASA
"Bruce McCandless used an MMU to become the first untethered astronaut in space," says Cichan. (The 1984 excursion led to the famous photo of an astronaut floating above the Earth against the blackness of space.)
This history of reliability, combined with the ostensible cost savings and reduced weight of sending a small spacesuit instead of a large lander, should be attractive to NASA — but it remains to be seen if the space agency selects the idea.
Cichan sounds confident NASA may go for it.
"From a technology development point of view, particularly for an orbital mission, we have almost everything we need today, or we're on a development pathway to get it," he says. "Mars really is within our reach within about a decade, and these ideas are us making the most use of funding that Congress has laid out."
Space experts to meet in Tokyo to discuss ways to deflect asteroids
Scientists and engineers from all over the world will gather from 15 to 19 May in Tokyo, Japan, at the 5th Planetary Defence Conference (PDC) to discuss the threat posed by asteroids and comets. This bi-annual conference, organized by the International Academy of Astronautics (IAA) will discuss actions that might be taken to deflect an incoming object. At the first conference on asteroid impact prevention to be held in Asia, space experts from Airbus will provide an update on the NEOShield-2 project and will introduce an alternative kinetic impactor demo mission scenario, called NEOTWIST.
NEOShield-2 is a collaborative project that started in 2015 as part of the EU's Horizon 2020 programme and is developing the necessary space mission technologies to divert hazardous asteroids. The project is also investigating how to precisely measure any deflection attempts and how to carry out in-situ investigations. Astronomical observations, modelling, simulations and physical characterization of Near Earth Objects (NEOs) are being studied to better understand their physical properties. The research is also looking at a European strategy for future research and mission-related endeavours.
The NEOShield-2 team comprises 11 European partners under the coordination of Airbus in Friedrichshafen (Germany). Airbus in Toulouse (France) and in Stevenage (United Kingdom) are also part of the project. The project overview and its achievements reached so far will be presented in Tokyo by Airbus’s Albert Falke, project manager and responsible project coordinator of NEOShield-2 towards the European Union.
Kilian Engel, space expert at Airbus and Line Drube, postdoctoral researcher at the German Aerospace Center (DLR-Berlin), will present the NEOTωIST concept, an element of the NEOShield-2 project. NEOTωIST is a test mission to demonstrate "deflection technology readiness" and to answer the uncertainties in the asteroid deflection physics that cannot be proven on Earth.
Albert Falke, who heads Airbus’s asteroid deflection programme, said: "A deflection test mission, perhaps in a joint effort by several space agencies, is needed to develop technologies to enable us to deal with an asteroid threat. Most importantly, it would give us real data which is vital for the development of a mission in cases of real emergency."
A deflection test mission with an asteroid in space is the only way to validate existing impact models and to check that the current computer models of deflection predictions are accurate.
Ulrich Johann, Head of Future Programmes, at Airbus’s Science and Earth Observation department in Friedrichshafen, Germany said: "The NEOTωIST concept combines an impactor and an in situ monitoring module in a single spacecraft. This cost-effective approach providing on the spot observation capabilities should lead to more launch opportunities for NEOTωIST compared to other concepts."
Most demonstration mission concepts to date rely on changing an asteroid's orbit around the sun and require a second spacecraft that follows the asteroid for some time after the impact to measure the very small shift in its orbit. In contrast, the Airbus concept is to impact a well-characterized asteroid at some distance from its rotation axis, and thereby change the asteroid's rotational period. This change can be measured by Earth-bound telescopes.
In parallel, a small observation module which is separated from the main kinetic impactor spacecraft just before impact, will also measure this rotation change. These close-up observations will give detailed information about the impact location and success of the mission.
Erste Radiobeobachtungen des einsamen planetenartigen Objekts OTS44 zeigen eine staubige protoplanetare Scheibe ähnlich der eines jungen Sterns. Das ist unerwartet: Laut den herkömmlichen Modellen sollte ein so massearmes Objekt nicht so entstehen können wie ein Stern, also beim Kollaps einer Gaswolke. Offenbar sind sich Sterne und planetenartige Objekte ähnlicher als bisher angenommen. Das neue Ergebnis einer Gruppe um Amelia Bayo, zu der auch mehrere Astronomen des Max-Planck-Instituts für Astronomie gehören, ist am 18. Mai 2017 in den Astrophysical Journal Letters erschienen.
Bild: Johan Olofsson (U Valparaiso & MPIA)
Neue Beobachtungen des einsamen planetenartigen Objekts OTS44 haben starke Hinweise darauf ergeben, dass dieses Objekt ähnlich entstanden ist wie herkömmliche Sterne oder Braune Zwerge – ein überraschender Umstand, der herkömmliche Modelle der Stern- und Planetenentstehung vor eine Herausforderung stellt. Für diese Beobachtungen hatte die Astronomengruppe unter der Leitung von Amelia Bayo, zu der auch Forscher des Max-Planck-Instituts für Astronomie gehören, das ALMA-Observatorium in Chile genutzt.
Die Beobachtungen erlauben die Abschätzung der Masse des Staubanteils in der Scheibe rund um OTS44. Mit dem Ergebnis reiht sich OTS44 ein bei Objekten wie Sternen und Braunen Zwergen (letztere sind "verhinderte Sterne", mit zu wenig Masse für langanhaltende Kernfusionsreaktionen ): Alle diese Objekte haben offenbar bestimmte ähnliche Eigenschaften, darunter einen ähnlichen Zusammenhang zwischen der Masse des Staubs in der Scheibe und der Masse des Zentralobjekts. Das neue Ergebnis ergänzt bereits länger bekannte Ähnlichkeiten, insbesondere den Umstand, dass OTS44 nach wie vor wächst, indem es Materie von seiner Scheibe auf sich zieht – auch das eigentlich charakteristisch für junge Sterne.
Ähnlichkeiten mit Sternen und Braunen Zwergen
Insgesamt sprechen diese Befunde stark dafür, dass OTS44 in der gleichen Weise entstanden ist wie Sterne und Braune Zwerge, nämlich durch den Kollaps einer Gas- und Staubwolke. Den herkömmlichen Modellen nach sollten sich Objekte mit so geringer Masse wie OTS44 aber gar nicht auf diese Weise bilden können. Eine mögliche Alternative, nämlich die gleichzeitige Bildung mehrerer Objekte, von denen OTS44 nur eines ist, widerspricht den Beobachtungen, die keine solchen Begleiterobjekte in der Nähe von OTS44 zeigen.
Die Stärke der bei Millimeter-Wellenlängen empfangenen Strahlung weist auf die Anwesenheit von ungefähr millimetergroßen Staubkörnern hin. Auch das ist unerwartet. Unter den Bedingungen, wie sie in der Scheibe rund um ein astronomisches Objekt geringer Masse herrschen, sollte Staub sich eigentlich gar nicht zu solcher Größe (oder darüber hinaus) zusammenballen können. Die Staubteilchen rund um OTS44 sind allerdings trotzdem am wachsen – und könnten sogar auf dem Wege sein, später einmal eine Art Mini-Mond des Objekts zu bilden; eine weitere Ähnlichkeit mit Sternen und ihren Planetensystemen.
Amelia Bayo (Universität Valparaiso), die Leiterin des Forschungsprojekts, sagt: "Je mehr wir über OTS44 wissen, umso größer wird seine Ähnlichkeit mit einem jungen Stern. Aber die Masse des Objekts ist so gering, dass sich OTS44 den gängigen Theorien zufolge gar nicht wie ein Stern hätte bilden dürfen!"
Thomas Henning vom Max-Planck-Institut für Astronomie ergänzt: "Es ist schon beeindruckend, dass wir mithilfe eines Observatoriums wie ALMA rund eine halbe Erdmasse an Staub rund um ein Objekt mit zehn Jupitermassen auf eine Entfernung von 500 Lichtjahren sehen können. Aber die neuen Daten zeigen uns auch die Grenzen unseres Wissens. Offenbar müssen wir über die Entstehung von astronomischen Objekten mit niedriger Masse noch viel lernen!"
Ausführliche Beschreibung: Erste Radiobeobachtungen einer Planeten-Scheibe: Objekt entstand offenbar ähnlich wie ein Stern
Eine neue Untersuchung des einsamen planetenähnlichen Objekts OTS44 gibt Hinweise darauf, dass dieses Objekt in ähnlicher Weise entstanden ist wie Sterne und Braune Zwerge – ein überraschendes Ergebnis, das herkömmliche Modelle zur Stern- und Planetenentstehung vor eine Herausforderung stellt. Die Untersuchung, durchgeführt von einer Astronomengruppe unter der Leitung von Amelia Bayo vom Max-Planck-Institut für Astronomie, nutzte das ALMA-Observatorium, um den Staub der Scheibe um OTS44 zu beobachten.
Von kollabierenden Wolken zu Sternen
Sterne entstehen, wenn Teile einer gigantischen Gaswolke unter ihrer eigenen Schwerkraft zusammenstürzen. Aber nicht bei jedem solchen Kollaps entsteht ein Stern. Die entscheidende Größe ist die Masse: Besitzt das resultierende Objekt eine hinreichend große Masse, dann ist die Gravitation stark genug um die innersten Regionen zu so hohen Dichten zusammen zu pressen, und auf so große Temperaturen zu erhitzen, dass Kernfusionsreaktionen einsetzen, bei denen Wasserstoffkerne (Protonen) zu Helium verschmelzen. Dann ist per Definition ein Stern entstanden: ein durch die eigene Schwerkraft zusammengehaltener Plasmaball, in dessen Zentrum Kernfusion stattfindet. Die dabei laufend freigesetzte Energie wird nach außen transportiert und lässt den Stern hell leuchten.
Anfangs ist der neugeborene Stern noch von den Überresten der Gaswolke umgeben. Im Laufe des Kollapses haben Wolke und Stern dabei begonnen, merklich zu rotieren – analog dazu, wie ein Eiskunstläufer seine Drehgeschwindigkeit erhöht, indem er seine Arme an den Körper zieht. Durch die Rotation wird das verbleibende Material zu einer Scheibe aus Gas und Staub auseinandergezogen, die den jungen Stern umgibt und protoplanetare Scheibe genannt wird. Ihrem Namen entsprechend bilden sich in dieser Scheibe die Planeten: Die Staubteilchen klumpen zu immer größeren und größeren Teilchen zusammen bis die resultierenden Objekte dann sogar so groß sind, dass sie sich unter dem Einfluss ihrer gegenseitigen Schwerkraft zu Planeten zusammenziehen können. Dabei können zum einen dichte Gesteinsplaneten wie unserer Erde entstehen, mit Durchmessern zwischen tausenden und zehntausenden von Kilometern. Zieht ein solches Objekt Reste des Scheibengases auf sich entstehen Gasriesen, in unserem Sonnensystem beispielsweise der Jupiter.
Hat das beim Wolkenkollaps entstehende Objekt dagegen eine Masse zwischen rund 7 Prozent und rund einem Prozent der Sonnenmasse – genauer: zwischen 75 und 13 Jupitermassen – dann entsteht kein Stern, sondern ein Brauner Zwerg: eine Art verhinderter Stern, in dessen Kernregionen zwar zwischenzeitlich in beträchtlichem Umfang Fusionsreaktionen mit Deuteriumkernen (schweres Wasser, ein Proton plus ein Neutron) stattfinden, der allerdings nicht genug Masse besitzt, als dass dort die für Sterne typische langfristige Phase der Wasserstoff-Fusionsreaktionen einsetzen könnte.
Der seltsame Fall von OTS44
Können beim Kollaps Objekte mit noch geringerer Masse entstehen – etwa mit den typischen Massen von Planeten? Eine detaillierte Analyse des Objekts OTS44, veröffentlicht 2013 von einer Gruppe unter der Leitung von Viki Joergens vom Max-Planck-Institut für Astronomie (MPIA) spricht deutlich für diese Möglichkeit. OTS44 ist nur rund zwei Millionen Jahre alt – auf den Zeitskalen von Sternen oder Planeten ein neugeborenes Baby. Das Objekt hat geschätzt eine Masse von 12 Jupitermassen und fliegt ohne irgendeinen nahen Begleiter alleine durch den Weltraum. Es ist dabei Teil der Chamäleon-Sternentstehungsregion im südlichen Sternbild Chamäleon, etwas mehr als 500 Lichtjahre von der Erde entfernt. Dort werden nach wie vor zahlreiche neue Sterne aus kollabierenden Gas- und Staubwolken geboren.
Genau wie ein junger Stern ist OTS44 von einer Scheibe aus Gas und Staub umgeben – eines von nur vier Objekten mit derart niedriger Masse (rund einem Dutzend Jupitermassen oder weniger), von denen bekannt ist, dass sie eine solche Scheibe besitzen. Hinzu kommt dass OTS44 nach wie vor wächst, indem es Material aus seiner Scheibe auf sich zieht. Die Scheibe besitzt eine gehörige Masse; sowohl sie als auch das nach wie vor auf OTS44 fallende Material (Akkretion) sind deutliche Hinweise darauf, dass es keinen grundlegenden Unterschied zwischen der Entstehung von Objekten mit niedriger Masse und Sternen gibt. OTS44 dürfte dabei die niedrigste Masse von allen Objekten haben, bei denen man sowohl eine Scheibe als auch einfallendes Material nachgewiesen hat.
Brauner Zwerg versus planetenähnliches Objekt
Wir haben es bislang vermieden, OTS44 entweder als Braunen Zwerg oder als etwas anderes zu bezeichnen. Die Nomenklatur ist an dieser Stelle auch nicht eindeutig. Einige Astronomen nennen jedes Objekt, das sich durch direkten Kollaps einer Gaswolke gebildet hat, aber selbst kein Stern ist, einen Braunen Zwerg. Nach dieser Definition können nur Objekte, die sich in einer Scheibe rund um ein Zentralobjekt gebildet haben, Planeten sein. Eine alternative Definition bezieht sich darauf, dass ein Objekt wie OTS44 nicht genug Masse für die für Braune Zwerge typische Episode enthält, in der ein beträchtlicher Teil des Deuteriums fusioniert; damit ist OTS44 dieser Definition gemäß kein Brauner Zwerg. Als Kompromiss bezeichnen wir OTS44 im folgenden als „planetenähnliches Objekt“.
Während der Fall von OTS44 zeigt, dass auch planetenähnliche Objekte durch Kollaps entstehen können, ist der genaue Ablauf alles andere als klar. Für die Entstehung von Objekten mit wenig Masse, seien es sehr leichte Sterne, Braune Zwerge oder Einzel-Planeten, gibt es im Prinzip zwei Möglichkeiten – die im Falle von OTS44 aber beide problematisch sind. Das erste wäre ein direkter Kollaps einer kleineren, isolierten Wolke. Aber den derzeitigen Modellrechnungen nach ist es unwahrscheinlich, dass ein so massearmes Objekt wie OTS44 auf diese Weise entsteht.
Deutlich wahrscheinlicher ist die Alternative, dass sich OTS44 nämlich aus einer größeren kollabierenden Wolke gebildet hat, die fragmentiert ist und anstatt eines einzigen größeren Himmelskörpers mehrere Objekte gebildet hat, darunter OTS44. Das passt allerdings nicht zu den Beobachtungen. OTS44 hat keine Begleiter. Und die Annahme, dass OTS44 zwar ursprünglich Teil eines Mehrfachsystems war aber dann hinausgeschleudert wurde, ist ähnlich problematisch. OTS44 ist schließlich noch sehr jung – das Geburts-System hatte nicht genügend Zeit, sich in Einzelsterne und/oder einzelne Braune Zwerge aufzulösen. Man sollte es demnach in der Nähe von OTS44 nachweisen können. Doch innerhalb von 10.000 astronomischen Einheiten (10.000 Mal dem mittleren Abstand Erde-Sonne), wo man die Geschwister von OTS44 finden müsste, gibt es nur ein einziges weiteres Objekt, und das sieht nicht so aus, als sei es in einem Mehrfach-Kollaps entstanden.
Mit ALMA auf Staubsuche
Offenbar besteht Klärungsbedarf. Das motivierte eine Gruppe von Forschern unter der Leitung von Amelia Bayo (Universität Valparaiso, Chile), mehr über OTS44 herauszufinden. Zu der Gruppe gehören eine Reihe von aktuellen und ehemaligen Mitarbeitern des Max-Planck-Instituts für Astronomie (MPIA), und auch Bayo war ihrerseits Postdoktorandin am MPIA, bevor sie an die Universität Valparaiso wechselte. Über die verschiedenen Stationen einer Wissenschaftlerkarriere entstehen nicht selten internationale Kooperations-Netzwerke – in diesem Falle eine strategische Kooperation zwischen Astronomen an der Universidad de Valparaiso und der von Thomas Henning geleiteten MPIA-Abteilung Planeten- und Sternentstehung. Die zwei Institutionen sind noch auf weitere Weise verbunden: Anfang 2017 hat an der Universität Valparaiso eine astronomische Max-Planck-Tandem-Gruppe die Arbeit aufgenommen. Mit solchen Tandem-Gruppen fördert die Max-Planck-Gesellschaft die internationale Zusammenarbeit mit bestimmten exzellenten Forschungsinstitutionen.
In diesem speziellen Fall gehörten zu der Gruppe, die Bayo für Beobachtungen von OTS44 zusammengerufen hatte, auch mehrere Mitglieder mit den richtigen Qualifikationen und mit Erfahrung für Beobachtungen mit dem ALMA-Observatorium: Einer Konstellation von 50 Radioantennen für den Nachweis von Millimeter- und Submillimeter-Strahlung, die von einem internationalen Konsortium in der Atacama-Wüste in Chile betrieben wird.
Die Astronomen beantragten ALMA-Beobachtungszeit, um die Scheibe von OTS44 bei Millimeter-Wellenlängen beobachten zu können. Licht dieser Wellenlänge ist besonders geeignet, um Staubkörner in protoplanetaren Scheiben nachzuweisen. Der Staub macht dabei ein Prozent oder mehr der Scheibenmasse aus; die genaue Abschätzung des Massenverhältnisses ist Gegenstand aktueller Forschung. Zumindest in den Scheiben um massereichere Objekte sind die Staubkörner der Schlüssel zur Planetenentstehung.
Staubmassen und ein überraschend allgemeiner Zusammenhang
Für Millimeterwellen ist die Scheibe optisch dünn, mit anderen Worten: Beobachtungen zeigen die Millimeterwellen-Strahlen des gesamten Staubs in der Scheibe. (In einer optisch dicken Scheibe würden wir nur Strahlung von den oberen Schichten empfangen; die tieferen Schichten würden von den oberen Schichten abgeschattet.) Damit lässt sich aus der empfangenen Strahlung die Gesamtmenge an Staub in der Scheibe abschätzen – wobei das Ergebnis allerdings auch noch von der Scheibentemperatur abhängt. Temperaturabschätzungen für solche Scheiben in Abhängigkeit von der gemessenen Gesamtstrahlung ergeben für die OTS44-Scheibe Werte zwischen 5.5 und 20 Kelvin. Das ergibt eine Staubmasse zwischen 7 Prozent der Erdmasse (für den niedrigsten Temperaturwert) und 64 Prozent (für den höchsten).
Diese Massenabschätzungen sind ein weiterer Hinweis auf die Ähnlichkeiten zwischen Sternen und Objekten mit niedrigerer Masse. Systematische Untersuchungen hatten bereits früher gezeigt, dass die Masse des Zentralobjekts und die Masse des Staubs in der umgebenden Scheibe für junge Sterne und Braune Zwerge systematisch zusammenhängen. Die Datenpunkte für OTS44 passen genau in dieses Bild und scheinen Ausdruck desselben Zusammenhangs zu sein – ein Anzeichen dafür, dass in all diesen Fällen derselbe Mechanismus am Werke ist, für Zentralobjekte mit rund einer Hundertstel Sonnenmasse ebenso wie für solche mit mehreren Sonnenmassen.
Staubkörner ungewöhnlicher Größe
Eine weitere interessante Konsequenz ergibt sich direkt aus dem Umstand, dass die Scheibe überhaupt beträchtliche Mengen an Millimeterstrahlung aussendet. Den aktuellen Modellen zur Planetenentstehung zufolge ist das überraschend: Solche größeren Staubkörner sollten sich in einer Scheibe um ein Objekt mit so geringer Masse gar nicht erst gebildet haben können. In solch einer Scheibe umkreisen die Staubkörner das Zentralobjekt wie Mini-Planeten und folgen dabei den Gesetzen, die Johannes Kepler für die Planetenbewegung bereits im frühen 17. Jahrhundert fand.
Das Gas dagegen besitzt einen inneren Druck und bewegt sich daher etwas anders. Insbesondere rotiert es langsamer um das Zentralobjekt. Die Staubkörner werden durch das langsamere sie umgebende Gas abgebremst und driften nach innen, wo sie schließlich auf den Zentralkörper fallen. Es gibt Argumente dafür, dass diese für die Staubkörner fatalen Mechanismen bei Zentralobjekten niedriger Masse besonders ausgeprägt sind. Aus den entsprechenden Rechnungen folgt, dass die Staubkörner eigentlich weitgehend hätten verschwinden müssen – und das bevor sie die Gelegenheit hatten, zu den beobachteten millimetergroßen Teilchen zusammenzuklumpen.
Sind die millimetergroßen Teilchen einmal da ist die Situation weniger problematisch – mit ihrer größeren Größe und Masse beeinflusst das Gas diese Teilchen weit weniger stark als ihre kleineren Verwandten. Warum diese größeren Teilchen überhaupt in der Scheibe entstehen konnten, ist derzeit noch nicht verstanden. Aber es eröffnet die Möglichkeit, dass in den Scheiben um solch ein einsames planetenähnliches Projekt sogar noch größere Staubteilchen wachsen können – und die Entwicklung vielleicht sogar bis zu regelrechten Mini-Monden weitergeht.
Ähnlichkeiten mit jungen Sternen
Insgesamt zeigen die neuen Ergebnisse, dass OTS44 einem jungen Stern in bestimmter Weise noch ähnlicher ist als gedacht. Nicht nur, dass er von einer Scheibe umgeben ist, nicht nur, dass er nach wie vor wächst indem er sich Scheibenmaterial einverleibt: auch das Verhältnis der Masse des Staubes in seiner Scheibe zur Masse von OTS44 fügt sich in den für Sterne und Braune Zwerge gültigen Zusammenhang ein.
Offenbar bedürfen die heutigen Modelle, die für Objekte niedriger Masse keine Entstehungsmöglichkeit aus dem direkten Kollaps einer Gaswolke vorsehen, der Überarbeitung. Beobachtungen wie diese hier an OTS44 weisen uns dann hoffentlich die richtige Richtung zur Entwicklung besserer Modelle, und damit eines tieferen Verständnis der Entstehung von Objekten mit niedriger Masse im Universum.
“I didn’t want to screw it up,” thought Kate Rubins, the first person to carry out this experiment in microgravity.
The International Space Station is one big research laboratory. Its earliest research objectives, back in 2000, were pretty straightforward: keep humans alive. Since then, the number of experiments conducted aboard the station has ballooned, and astronauts and cosmonauts spend their days studying how terrestrial science and technology works in microgravity. Over the years, the station’s residents have grown zucchini, beheaded flatworms, maneuveredhumanoid robots, tended to mouse embryos, watched the muscles of zebrafish atrophy, and drawn their own blood, using their own bodies as test subjects. Scrolling through NASA’s full list of experiments, one gets the sense that almost any experiment that can be done in a lab on Earth can be replicated in one floating 200 miles above.
So it shouldn’t be too surprising that humans have successfully sequenced DNA in space.
Last summer, NASA dispatched Kate Rubins, a microbiologist with a doctorate in cancer biology, to try it for the first time. Rubins has spent her career studying infectious diseases and worked with the U.S. Army to develop therapies for the Ebola and Lassa viruses. She has sequenced the DNA of different organisms plenty of times on the ground, but the process was a little bit more nerve-wracking on the space station. “I didn’t want to screw it up,” she says.
I spoke to Rubins during her recent visit to NASA headquarters in Washington, D.C. about the experiments she worked on during her four-month stint on the ISS. Our conversation, edited for length and clarity, is below.
But first, a brief rundown of how DNA sequencing actually works. Rubins used a specially made biomolecule sequencing device, a miniature version of the microwave-sized hardware on Earth. DNA samples are fed into its protein nanopores, tiny structures embedded in a synthetic cell membrane. The device sends an ion current through this membrane. When the bases of DNA—guanine, adenine, thymine, and cytosine—move through nanopores, they each create a change in the current. The device measures these tiny disruptions, and scientists use them to determine the sequence of the bases. For the human carrying this out, it’s actually pretty easy.
OK, let’s go.
Koren: So when you first got to the space station, knowing what you know about how communicable disease works, did you ever have a moment when you realized, I’m in a giant tube of germs?
Rubins: So we’re in a giant tube of germs all the time, right? Not to scare you. Sitting here, this room is filled with germs. Most germs aren’t bad. You’re in a microbial environment all the time. What’s interesting is that we’ve actually had this microbial environment that’s been separate from Earth for 16 years. We haven’t had real problems with disease outbreaks or that kind of thing happening on the space station, but it is interesting to potentially study its microbial environment, what different species of bacteria there are, and how that changes over time. I would actually say it’s a little bit better, from an infectious disease perspective, to be isolated. So you’re with three or six people, but you actually have less chance of being sick because it’s not like you’re going through an airport or a subway ride where you’re in contact with a bunch of people.
Koren: How did you start preparing for the DNA-sequencing experiment?
Rubins: We’d been working on it for a while. One of the questions we had was, how is the equipment going to survive launch? So we did launch vibration tests. We were also unsure about what would happen in microgravity—you get a lot of bubbles forming [in the solution]. Could we prevent bubbles from forming? We ended up deciding to sequence a mix of non-pathogenic viruses, bacteria, and mouse DNA because that gives you the range and complexity all the way from virus to mammalian organism.
Koren: Was there doubt it would work?
Rubins: Yeah, it was really an experiment. We were testing this technology and our question was, is this going be successful? And it was, luckily. But that’s pretty much everything in science. You have a hypothesis, you go in, you test it, analyze the results, and see if you have to change anything about the experiment.
Koren: How did the experience compare to sequencing DNA on Earth?
Rubins: I was surprised at how well it worked. I had tried it out a few times on the ground just to see how the mechanics of loading everything would work, and then it’s pretty different in microgravity, right? You put the pipette on the sequencing flow cell, and you shoot back off in the opposite direction with the same amount of force that you put on the pipette. Anytime you’re handling something, you have to stabilize yourself, so that took a little bit to get used to. I brought some foot restraints over and got myself hooked in. The first time I did it, I had a head lamp on so I could see really well, and some magnifying glasses.
Koren: How many runs did it take before it worked?
Rubins: It was actually successful on the first try, so that was great. We had some extra samples just in case it didn’t work the first time, so we started actually changing the experiment a little bit. We altered a few parameters, like the length of time that the reaction runs. They all worked.
Koren: What was your reaction after that first successful run?
Rubins: I was extremely excited. I was really nervous loading it the first time. I’m usually not nervous when I’m just doing a normal bit of pipetting, but I didn’t want to screw it up. There was a little bit of adrenaline going. It’s within 10 minutes that you start to see the first sequence coming through.
Koren: Did it feel like 10 minutes? Because when you’re anticipating something, time can feel like it’s moving slowly.
Rubins: Oh, no! I was like, I can’t even be here. I’ve got to float away and try to keep myself busy. And then I’d come back and check again, and then I’d float away again. We had a communications loop open with the ground team, so when we did start to see everything come through, they put the speaker on so I could hear them all clapping and cheering.
Koren: You also spent some time culturing human heart cells on the ISS. What was that like?
Rubins: You’re tending to the cells—you have to change the media [in the cell culture], you have to resupply them with nutrients. Instead of having the open cell-culture plate, they’ve got lure locks that are designed for space, and you can change the media with a little syringe. It took quite a long time to do the cell-culture change. I was nervous because I didn’t want to contaminate the cell culture; if you get bacteria in there, it’ll overgrow your culture and kill the cells and ruin the experiment. You have to work on very sterile techniques. It’s like prepping for surgery. You don’t want any microbes getting in the patient.
Koren: You’ve said you watched the heart cells beat in unison. How many cells does it take to see that?
Rubins: You can see 20 to 100 cells. For the most part, they’re in sheets or forming clumps or groups of cells, so you can see them together just synchronize that beating.
Koren: And is that weird to see?
Rubins: It was very cool. When I pulled the microscope out, the cosmonauts would come down from the Russian segment of the space station and everybody would float past because they liked watching it. There’s something fascinating about seeing down to the microscopic level and actually watching these heart cells beat.
Earth, Mars, and Titan all have channels, but different geologic pasts.
At this point, we’ve worked out the basics of the processes that produced the topography around us here on Earth. But other worlds in our solar system have very different landscapes that could partly be the result of foreign processes. The distant glimpses we get of these worlds make revealing those landscape histories a real challenge. Reconstructing a crime from a detailed inspection of a crime scene is one thing, doing it through a telescope is another.
Rivers are, in a way, topography bystanders that always flow downhill. The channels they carve certainly modify the landscape, but their paths reflect the elevations around them. They can also tell you about past topography if you know how to look. A team led by City University of New York researcher Benjamin Black sought to apply this concept not just to the Earth, but also to the two other worlds where we see river channels—Mars and Titan.
The researchers distinguished between long-wavelength topography (think continents and ocean basins on Earth) and short-wavelength topography (think mountain ranges within continents). The differing scales signify different processes, with smaller features resulting from local interactions between Earth’s tectonic plates rather than the fundamental difference between continental and ocean crust.
Playing with a simulation of an evolving landscape, the researchers demonstrate how rivers record these two processes. If you only deform an initially flat landscape to make long-wavelength topography, river channels dutifully trace simple, orderly lines from high elevation to low. But as you also push up localized topography, river channels deviate from that large-scale pattern more and more as “downhill” becomes a spatially variable concept.
Of course, if you stop pushing up localized topography, those rivers will eventually carve through the “bumps” and return to the orderly, large-scale pattern.
The researchers mapped out river channels on Earth, Mars, and Titan, and the team then compared the paths of those channels to a sequence of CSI-image-enhancement-style elevation maps. At the fuzziest level, only the very broadest elevation changes are apparent, and the correlation with river directions is assessed. The calculation is repeated for higher and higher resolution elevation maps to find out how much the correlation improves. If rivers coexisted with complex topography, the correlation will start out low and increase markedly as the hills and mountains diverting rivers come into focus. If rivers mainly flowed across long-wavelength topography, though, the correlation will start much higher and improve little as you increase the resolution.
For Mars and Titan, the correlation between river channels and the lowest-resolution elevation maps was pretty good. For Earth, though, the correlation started out very low. In other words, Earth’s plate tectonics have added a level of fine-scale complexity that Mars and Titan lack, and its rivers are more convoluted as a result.
On Mars, it looks like the present topography—dominated by a low-elevation northern hemisphere and a region of volcanic highlands near the equator—was already in place when water cut its river valleys. That implies that there weren’t any significant plate-tectonics-like processes active during Mars’ early days when water flowed across its surface.
The researchers describe Titan’s history as “the most enigmatic." We have evidence that Titan is (or was relatively recently) geologically active, yet its hydrocarbon river channels fit the long-wavelength topography well. The northern pole is an exception, with river channels that deviate a little more from the broader pattern.
Overall, the researchers say this probably means that Titan’s recent geological activity is, itself, large-scale. For example, it could be that elevation differences are being driven by global patterns of melting and freezing beneath its outer water ice layer, thickening and thinning different regions.
The northern pole is pretty puzzling, though. Titan’s atmospheric circulation carries hydrocarbons toward the pole. The river channels also drain toward the pole, so it’s not clear what process is sending material back southward.
While Mars and Titan are the only two other worlds where we’ve identified channels carved by liquid rivers, the researchers point out that a similar analysis could be done with other things that flow downhill—like the hot volcanoes of Venus or the cold “cryovolcanoes” of Pluto. Either could potentially preserve signs of shifting landscapes.
LIGO could detect gravitational waves’ permanent space-time warp
Like a sweater stretched too often by wide shoulders, space-time can be permanently warped by the gravitational waves that constantly ripple through it. This distortion, called gravitational wave memory, could allow us to detect waves previously beyond our reach – even if we can’t see the event that caused them.
This offers hope that we may be able to find some of the universe’s most exotic objects.
Gravitational waves are created by massive objects moving through space-time. In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) first detected a gravitational wave caused by two black holes spiralling towards one another and merging. Since then, theorists have been hard at work figuring out what such waves from other events and objects would look like.
Some of the most exotic objects in physics, such as evaporating black holes, cosmic strings and even possible extra dimensions, would induce gravitational waves at much higher frequencies than we can currently detect.
But there is still hope that these elusive objects could leave a detectable signal, say Lucy McNeill and her colleagues Eric Thrane and Paul Lasky at Monash University in Melbourne, Australia.
If two people were floating near, say, a pair of merging black holes, the space between them would grow and shrink as space-time was stretched and distorted by gravitational waves.
Once the black holes merged and the waves ceased, this oscillation would stop – but the two people would be at a different distance apart to when they started. Memory of the gravitational waves would leave them slightly further apart or closer together.
This permanent distortion of space-time creates a signal 10 to 100 times weaker and with a frequency much lower than the original one from the oscillating gravitational wave. It could also extend in all directions, even if the gravitational waves themselves were beamed in one specific direction.
The difference in frequency means that the kinds of event for which LIGO and similar detectors can spot gravitational waves will have too low a frequency for them to also pick up the memory signal.
But if there are astrophysical events that produce gravitational waves at frequencies too high for LIGO to spot, their memory signals might fall easily into the observatory’s detection range, thus allowing us to pick them up. McNeill and her colleagues call these “orphan” signals because the parent wave is not detectable.
“We can use LIGO to probe the universe for gravitational waves that were once thought to be invisible to it,” says McNeill. “LIGO definitely won’t be able to see the oscillatory stretching and contracting, but it will be able to detect the memory signature if such objects exist.”
In fact, memory signals could supply the first definitive proof that many objects that would emit high-frequency gravitational waves do exist. Even objects at the less-esoteric end of the spectrum, such as small primordial black holes, have not yet escaped the realm of theory.
“The problem is that the astrophysical situations that predict gravitational waves at those very high frequencies are quite speculative,” says Marc Favata at Montclair State University in New Jersey. “We don’t have solid evidence that such high-frequency sources exist – but they could if certain models are correct.”
Orphan memory signals could represent a ray of light for those theories, allowing researchers to find high-frequency sources without looking for the sources themselves.
“What excites me the most is that memory gives us a tool for probing a range of the gravitational-wave spectrum that was not previously accessible,” says Thrane. “Who knows what we may find?”
NASA Langley runs more wind tunnel tests on Space Launch System rocket models
The SLS rocket model is sleek and silver, standing 6 feet and then some inside the atmospheric wind tunnel at NASA Langley Research Center.
Research aerospace engineer David Chan is inside the tunnel, holding a long, hollow metal wand. At a signal, a big fan begins to pump outside air through the 14-by-22-foot tunnel cavity. A river of cool wind starts to gust over Chan and the rocket model, rapidly building to a tsunami of 35 mph.
Test engineer Les Yeh sends propylene glycol coursing into the wand, which heats the clear fluid to 270 degrees till it turns to smoke and ejects from the wand's tip like something out of "Harry Potter."
A line of smoke streams toward the rocket and the model launch tower standing beside it. Most of it flows past and disappears downstream. Some of it eddies and whirls around the rocket. And it all gives Chan and his colleagues more data on how ground winds can affect the real SLS booster when it stands on the launch pad at Cape Canaveral in Florida in a year or two and during the initial moments of liftoff.
"What we're trying to do is collect aerodynamic data to see how ground winds from various directions can affect the rocket," Chan said. "Basically, we're interested in crew safety. We don't want the rocket as it's lifting off to be pushed into the tower and contact the tower."
Dave Piatak, deputy lead for the SLS aerodynamics team at Langley, likens it to sticking your hand out the window of a car traveling at a high speed.
"There's a significant drag force," Piatak said. "And if you move your hand around the sideview mirror, you can find some areas where there's a little vortical flow and very unsteady. So it can not only push your hand back but buffet it."
Traveling at Mach 1, or 768 miles an hour at sea level, creates even harsher drag and flow environments.
"Even after decades of flying to orbit, to reaching that 17,500-mile-an-hour mark to get to orbit, we're still constantly learning new things as we test new configurations," Piatak said. "So new shapes of vehicles dictate a whole new aerodynamic database that needs to be developed."
The 14-by-22 is one of two wind tunnel tests on SLS models that NASA is running at its research center in Hampton.
The other is at the center's hypersonic Unitary Plan Wind Tunnel, where another smaller model is about to be subjected to blistering speeds of Mach 4, or four times the speed of sound.
There again, the idea is to ensure crew safety — this time when the twin solid rocket boosters separate from the core, said aerospace engineer Courtney Winski.
"It's a very short time period during the actual flight," said Winski, lead researcher for the SLS solid rocket booster test. "But it's an important piece of the flight."
Important because when those empty boosters have done their job, spent their fuel and dropped away, any inadvertent recontact with the core rocket carrying a crew capsule or critical cargo could be catastrophic.
"That would be a bad day for all," Piatak said.
The Unitary Plan Wind Tunnel is one of a group of unique facilities created by an act of Congress in 1949 to test experimental aircraft, missiles and rockets at near-hypersonic speeds. NASA Langley's version has two test sections, one with a Mach range from 1.5 to 2.9, and the other from 2.3 to 4.6. The test section for the SLS model is about 4-foot square. But looks can be deceiving.
"You're only seeing a small portion of the massive industrial complex that surrounds us right now," Piatak said.
The entire complex includes six giant compressors powered by two massive motors capable of generating a combined 100,000 horsepower, said Winski. The compressors shoot air through huge steel pipes that snake throughout the facility. Other far smaller compressors and heat exchangers are installed along the tunnel piping. Nozzles control the air flow into the test chambers — one of which contains an SLS model being readied for its Mach 4 workout.
The SLS is the Space Launch System of super heavy-lift rockets that NASA has been developing with its commercial partners. The idea is to get space vehicles with enough oomph to send crews on deep-space missions and launch massive amounts of payload to assemble structures in space or colonize other planets or the moon.
The SLS system is expected to include the most powerful rocket ever built.
Of the four variants under development so far, two are intended to carry crew while the others are to haul up to 130 metric tons of cargo. They range in size from 322 to 365 feet. By comparison, the Saturn V rocket built to boost astronauts to the moon stood at 363 feet.
The model being tested now at NASA Langley represents the bigger of the crew versions, called SLS Block 1B Crew. The real thing could be boosting an Orion capsule carrying crew into lunar orbit as early as 2021 on what's known as Exploration Mission 2, or EM-2.
But prior to that, the smaller version, or SLS Block 1 Crew, is scheduled for a test flight to the moon in late 2018 or early 2019. That version has already been tested at Langley.
It's unclear yet if that EM-1 mission will have test pilots aboard.
"The official word on that is the White House has requested an assessment of whether or not we could put a crew earlier than we had planned on that first EM-1 flight," Piatak said.
He, his team and others have made recommendations on whether it would be feasible based on economics and scheduling. He declined to say what their recommendations were.
Quelle: Daily Press
NASA investigating damaged SLS tank section
WASHINGTON — NASA and Boeing are investigating a recent mishap at the Michoud Assembly Facility that damaged a portion of a liquid oxygen tank being developed for the Space Launch System.
Kim Henry, a spokesperson for NASA’s Marshall Space Flight Center, said May 10 that NASA and Boeing, the prime contractor for the SLS core stage, have established independent investigation teams to review an incident at Michoud one week earlier involving the rear dome of a liquid oxygen qualification tank. The mishap was first reported by NASA Watch.
The agency didn’t provide additional details about the incident, which took place in the Vertical Assembly Center at Michoud, used to weld large components of the SLS. The Vertical Assembly Center was shut down when the incident took place, Henry said. “NASA is evaluating next steps to safely resume operations.”
The damage was limited to the one dome section of the tank, which was not yet welded to the rest of the tank. “Assessments are ongoing to determine the extent of the damage,” she said.
Henry said that the incident was classified as a “Type B” mishap. Such a mishap, according to NASA documents, covers incidents that cause between $500,000 and $2 million in damage. No one was injured, she said.
The liquid oxygen tank involved in the incident was a qualification model, intended for testing, and not flight hardware. Henry said it wasn’t immediately clear how long the investigation would take.
The accident comes as other factors, some outside of NASA’s control, have threatened to delay development of the SLS. A tornado struck Michoud in February, damaging some buildings used for SLS and Orion work there. Agency officials estimated in March the repairs would delay work by two to three months.
The schedule for that launch may also depend on a decision to put a crew on EM-1, which is currently planned to fly without astronauts on board. NASA officials said last month that a report studying the feasibility of placing a crew on EM-1 has been completed and briefed to agency leadership and the White House, but no decision has been announced yet.
NASA decides not to place a crew on first SLS/Orion mission
WASHINGTON — NASA has decided it will not add astronauts to the first flight of the Space Launch System, a launch now delayed until some time in 2019.
In a media teleconference May 12, agency leaders said that while it was technically feasible to place a crew on the Exploration Mission (EM) 1 flight of SLS and Orion, cost, schedule and risk issues led NASA and the White House to decide to keep with current plans to fly the mission without astronauts.
“At the end of the day, we found it technically feasible to fly crew on EM-1, as long as we had a commitment of additional resources and schedule,” NASA Acting Administrator Robert Lightfoot said. However, after assessing what it would take to implement that plan, officials “decided that, while it was technically feasible, they really reaffirmed that the baseline plan we had in place was the best way for us to go.”
That decision, Lightfoot said, was made jointly by NASA and the White House. “We definitely sat with them after we heard the feasibility study and came to this conclusion together,” he said. He added that the new administration has been “incredibly supportive” of the study and NASA’s overall exploration plans.
Bill Gerstenmaier, NASA associate administrator for human exploration and operations, said that the study turned up fewer technical issues with putting a crew on EM-1 than he originally expected. “What I was surprised by was that I thought there would be a whole lot of really negative work that would actually maybe make this not very attractive to us,” he said.
“But when Robert and I look at this overall, it does add some more risk to us, because it’s the first crew on the vehicle,” he said. The work to add crew to EM-1 would have cost NASA an additional $600–900 million, and delay the launch likely to the first or second quarter of 2020.
“The culmination of changes in all three of those areas said that overall, probably the best plan we have is actually the plan we’re on right now,” Gerstenmaier said. “When we looked at the overall integrated activity, even though it was feasible, it just didn’t seem warranted in this environment.”
Gerstenmaier said a variety of issues with SLS and Orion contributed to the delay to 2019. “The fact that we’re running into some production problems is typical of almost any major development of this complexity,” he said. He added that the tornado that damaged the Michoud Assembly Facility in New Orleans in early February “really set us back in a big way.”
“This was a significant event for us,” Gerstenmaier said, but one he said will likely not have a major effect on the overall schedule.
NASA has not announced a more specific launch date for EM-1 yet other than 2019. Gerstenmaier said the agency would wait until a mishap investigation board at Michoud concludes its study of the tank accident. “We’re probably a month or two away from coming up with a final schedule,” he said.
The EM-1 delay could also push back EM-2, the first mission to carry a crew. That mission will also use an upgraded version of the SLS with the more powerful, and larger, Exploration Upper Stage, which requires some reconfiguration of ground systems at the Kennedy Space Center.
“We’ve been carrying, tentatively, an August 2021 date for EM-2,” Gerstenmaier said. “It will probably move somewhere to the right because of the relationship between EM-1 and EM-2.” A revised date for EM-2, he said, should come several months after the new date for EM-1.
“We continue to have a good dialogue with the White House. The administration has been very supportive of our plan,” he said. “They have not asked us to go to Mars by 2024.”
A massive barge got this SLS part to Alabama, now NASA will crunch it
NASA barge Pegasus at Redstone Arsenal dock in Huntsville, Ala. delivering the engine section test article for NASA's Space Launch System to Marshall Space Flight Center after a month long trip from NASA's Michoud Assembly Facility in New Orleans. (Bob Gathany / bgathany@AL.com)
The first large test section of NASA's Space Launch System core will roll slowly to an Alabama test stand this week in what's being called a key step toward America's next deep-space rocket.
"It's been a long time since the agency's had a program make it this far," Space Launch System program manager John Honeycutt said at Marshall Space Flight Center Tuesday.
Honeycutt spoke inside NASA's Pegasus barge, enlarged for its new SLS mission and docked now on the Tennessee River. The Pegasus had just brought a 40,000-pound engine core from NASA's Michoud Assembly Facility near New Orleans to Marshall for stress testing. If it passes, the part is "qualified" for spaceflight.
"The engine section is kind of the back part of the rocket," Honeycutt said, "where all the plumbing, if you will, gets connected to the RS-25 engines."
Marshall technicians will move the core "at a walking pace" approximately 7 miles from the river landing to Building 4619. There, it will be fitted with 3,000 data channels and 55 hydraulic lines. It will have a test stand basically built around it.
The hydraulic lines will apply controlled pressure to test the core's ability to survive launch pressure by squeezing, bending and crushing it. The test program will take until early next year to finish.
It took 17 days to get the test part upriver from Michoud to Marshall by way of the Mississippi, Ohio and Tennessee rivers. "What we did not expect was all the rain we had up the Mississippi in the St. Louis area," Pegasus barge team leader Alan Murphy said.
The crew had to park the barge for five days while water levels dropped low enough to insure its 213 feet height would make it under every bridge going downriver. "We did not want to hit a bridge," Murphy said. "It we hit a bridge, it's not going to be an 'oops,' it's going to be nationwide."
The engine core is the first of four core parts of the SLS heading for Marshall for stress testing in the coming year. All are being built in the Michoud facility near New Orleans.
Why not build new test stands there - as NASA is doing in Alabama - and test a few hundred yards from the manufacturing facility?
"You've got to look at your resources, the people, all of your moving equipment," said Tim Flores, SLS core stage integration manager. "It was much cheaper to just barge the equipment here and have these stands built here where we are actually a center of excellence for structural engineering."
"This is a milestone," Honeycutt said of the test part's arrival at the Marshall Space Flight Center. "It helps me to where I'm one step closer to that flight readiness review ... to say this rocket's ready to fly."
Honeycutt said SLS will share the load of space exploration with rockets built by commercial space companies such as SpaceX and Blue Origin.
"We need all of us to do the space exploration the nation has charted out for us to go do," he said. "The president and the Congress support SLS. SLS will give us the capability to deep space exploration for decades to come."
As for where Tuesday's barge docking puts NASA in the years' long process of building SLS, Honeycutt said he sees his current team "as the team that has got to close this out. If you want to do a baseball analogy, we're the closers."
Report criticizes development of SLS test stands
WASHINGTON — A rush to complete two test stands needed for development of the Space Launch System caused their cost to nearly double, even as the overall program suffered delays, according to a new report.
The May 17 report by NASA’s Office of Inspector General (OIG) found that the cost of the two test stands built at the Marshall Space Flight Center for testing SLS propellant tanks increased by more than 87 percent, to $76 million, as the agency overlooked potential long-term cost savings in a effort to expedite their construction.
NASA entered into an agreement with the U.S. Army Corps of Engineers in August 2013 to construct Test Stands 4693 and 4697 at Marshall, on the grounds of the Army’s Redstone Arsenal. The Corps of Engineers then awarded a contract to an Alabama construction company, Brasfield & Gorrie, to build the stands. The stands are large steel structures designed to perform load testing on the rocket’s liquid oxygen and liquid hydrogen tanks to simulate the conditions the tanks will experience during launch.
At the time of the contract award, NASA sought to have Test Stand 4693, for liquid hydrogen tank testing, done by May 2015 and Test Stand 4697, for liquid oxygen tank testing, by September 2015. NASA paid a $7.6 million premium for a compressed construction schedule in order to meet a planned December 2017 deadline for the first SLS launch.
The development schedule for SLS slipped, though, pushing back the first launch to November 2018 and, more recently, to some time in 2019. NASA was unable to recoup that premium because of the fixed-price nature of the contract.
The OIG report concluded that costs also increased because of changes in the design of the test stands. Those design changes were in large part caused when testing requirements for the tanks matured as the program advanced.
NASA had originally budgeted $30 million and $10.5 million for Test Stand 4693 and Test Stand 4697, respectively. The final costs for the two stands, OIG found, were $53.7 million and $22.3 million, with the construction completed in late 2016. The $76 million total cost represented an increase of 87.6 percent over the original budget.
“In short, rushing the decision regarding the test stands to support a December 2017 first flight raised the cost of constructing the stands by tens of millions of dollars,” the report concluded.
The report also criticized the decision to build the stands at Marshall without seriously considering alternative sites, notably the Stennis Space Center in Mississippi. The cost of building the liquid hydrogen tank stand at Stennis, Marshall officials said, was 23 percent more than the original cost of Test Stand 4693, but the OIG report noted that estimate was not originally documented and had to be recreated for the audit.
That analysis also did not take into account the lifecycle costs of the stands, in particular transportation costs. The tanks, built at the Michoud Assembly Facility in New Orleans, must be transported by barge to Marshall, a circuitous route that takes two weeks and costs $500,000. Transporting the tank to Stennis would take less than one week and cost $200,000.
“Without a thorough analysis of alternative construction sites, including complete life-cycle cost analysis to include operations and maintenance costs, as well as transportation of test articles through the expected useful life of the stands, it remains unclear whether NASA made the most cost effective decision for the Program and the Agency in the long run,” the report stated.
Astronomers scramble as ‘alien megastructure’ star dims again
The most famously weird star in our galaxy is acting up again. On Friday, 19 May, Tabby’s star began to dim, carrying on a history of mysterious dips in brightness. Astronomers are scrambling to point as many telescopes as possible at the star, which is 1,300 light-years away in the constellation Cygnus, to decipher its strange signal.
In 2015, a team of astronomers led by Yale’s Tabetha Boyajian saw the light from the star KIC 8462852 suddenly and repeatedly dip in brightness. The star dimmed by up to 22 per cent before it returned to normal.
Then, in 2016, a review of old photographic plates revealed that KIC 8462852 dimmed by 14 per cent between 1890 and 1989. The star, nicknamed Tabby’s star after Boyajian, faded by another 3 per cent over the four years it was observed by the Kepler space observatory.
Astronomers have come up with a huge variety of different potential explanations for the star’s strange behaviour. Some say it could be because of its interior dynamics, some say it could be surrounded by a swarm of asteroids and debris. Or maybe it’s dimming because it devoured a planet at some time in the past. Most famously, some astronomers have said that the dimming could be caused by an orbiting alien megastructure.
Because Tabby’s star has cultivated such an air of mystery, the response to its new dimming has been quick and enthusiastic, with some telescope observations of the star already planned over the next few days. If we’re lucky, new observations may just help us figure out what’s making KIC 8462852 dim (it’s probably not aliens).
'Alien Megastructure' Star Is at It Again with the Strange Dimming
The perplexing cosmic object known as "Boyajian's star" is once again exhibiting a mysterious pattern of dimming and brightening that scientists have tried to explain with hypotheses ranging from swarms of comets to alien megastructures.
Today (May 19), an urgent call went out to scientists around the world to turn as many telescopes as possible toward the star, to try and crack the mystery of its behavior.
"At about 4 a.m. this morning I got a phone call … that Fairborn [Observatory] in Arizona had confirmed that the star was 3 percent dimmer than it normally is," Jason Wright, an associate professor of astronomy at Pennsylvania State University, who is managing a study of Boyajian's star, said during a live webcast today at 2 p.m. EDT (1800 GMT). "That is enough that we are absolutely confident that this is no statistical fluke. We've now got it confirmed at multiple observatories, I think."
Star KIC 8462852, or Boyajian's star (also nicknamed "Tabby's star," for astronomer Tabetha Boyajian, who led the team that first detected the star's fluctuations), has demonstrated an irregular cycle of growing dimmer and then returning to its previous brightness. These changes were first spotted in September 2015 using NASA's Kepler Space Telescope, which was built to observe these kinds of dips in a star's brightness, because they can be caused by a planet moving in front of the star as seen from Earth.
But the brightness changes exhibited by Boyajian don't show the kind of regularity that is typical of a planet's orbit around its star, and scientists can't see how the changes could be explained by a system of planets.
Scientists have hypothesized that the changes could be due to a swarm of comets passing in front of the star, that they're the result of strong magnetic activity, or that it's some massive structure built by aliens. But no leading hypothesis has emerged, so scientists have been eager to capture a highly detailed picture of the light coming from the star during one of these dimming periods. This detailed view is what scientists typically call an object spectra. It can reveal, for example, the specific chemical elements that are in a gas. It can also tell scientists if an object is moving toward or away from the observer.
"Whatever's causing the star to get dimmer will leave a spectral fingerprint behind," Wright said during the webcast, which took place in the Breakthrough Listen laboratory at the University of California, Berkeley. "So if there is a lot of dust between us and the star … it will block more blue light than red light. If there is gas in that dust, that gas should absorb very specific wavelengths and we should be able to see that. And so, we've been eager to see one of these changes in one of these dips of the star so we can take some spectra."
But the scientists couldn't predict when the next dimming event would occur or how long it will last. (Dips detected by Kepler lasted for between two and seven days, according to Wright.) Professional-grade telescopes typically schedule observing time weeks or months in advance, so Wright and his colleagues knew their observations would have to come at the behest of colleagues who were already using the telescopes for other projects.
"We need to have a network of people around the world that are ready to jump on [and observe it]," Wright said. "Fortunately, Tabby's star is not too faint and so there are a lot of observers and telescopes … that have graciously agreed to take some time out of their science to grab a spectrum for us [tonight]."
Wright said the call had gone out to amateur as well as professional astronomers to observe Boyajian's star during this dimming period. The largest and most powerful telescopes that will heed the call are the twin 10-meter telescopes at the W.H. Keck Observatory in Hawaii. The team is working to gain observing time on at least three other large telescopes on the U.S., according to Wright.
The Breakthrough Listen initiative, which searches for signs of intelligent life in the universe, has also taken an interest in the star and will be observing it with the Automated Planet Finder telescope at Lick Observatory in California, according to Andrew Siemion, director or the Berkeley SETI Research Center, said in the webcast.
"It's Super Bowl Sunday," Siemion said of the atmosphere at the during the webcast. "There's a palpable tension."
Breakthrough and the Berkeley center are now trying to get some observing time on the Green Bank radio telescope in West Virginia, according to Siemion.
Boyajian was the astronomer at Yale University who led the team that initially spotted the star's brightness fluctuations. It was Boyajian who called Wright at 4 a.m. to confirm that the star is dimming.