OrbitalHub

The place where space exploration, science, and engineering meet

Domain is for sale. $50,000,000.00 USD. Direct any inquiries to contact@orbitalhub.com.

 

 

NASA dicit:

“NASA’s Curiosity Mars Rover has already descended from Vera Rubin Ridge, a region of Mount Sharp that it has been exploring for more than a year. But before it left, the rover took a 360-degree panorama of the area depicting its last drill hole on the ridge (at a location called “Rock Hall”), a new region it will spent the next year exploring (the clay unit) and its last view of Gale Crater’s floor until it starts ascending in elevation again.”

Video Credit: NASA/JPL-Caltech/MSSS

 

 

  • Facebook
  • Google
  • Slashdot
  • Reddit
  • Live
  • TwitThis
07-26-11

Interplanetary Internet

Posted by

 

Credits: NASA/JPL/Arizona State University

 

 

You know the frustration you experience when the new hit of your favorite band takes too long to download on your iPhone? Imagine 30 years from now (an optimistic estimate)… you are one of the happy colonists who work around the clock to build one of the first outposts on Mars.

 

 

At the end of your shift in the hydroponics, you head back to your luxurious 20mx10m quarters (the shoebox, as your relatives back on Earth like to call it), have a hot shower, and a delicious vegetarian dinner while enjoying the view over the Valles Marineris (the $100 million view, as you like to call it). You receive an email with a link to the new hit of your favorite Earth band, and after clicking on the link in your favorite Internet browser, you download the song in less than one second.

 

What’s wrong with this scenario? It describes what software engineers would call a wonderful user experience, but something is wrong with this picture… what is it?

 

One short story might give you a hint. In January 2004, when the two Mars Exploration Rovers, Spirit and Opportunity, landed on Mars, you could watch videos of the scientists in the mission control room at JPL cheering when receiving confirmations of successful landings. The detail that might have escaped you is that those confirmation messages traveled around 20 minutes through interplanetary space before reaching the room at JPL. The scientists were cheering at JPL 20 minutes after the landings happened. If anything went wrong, the bad news would have reached Earth too late to do anything about it. This kind of explains why the engineers that designed and built the rovers had to make sure that the rovers themselves were capable of making some decisions on their own.

 

To go back to our sci-fi novel attempt in the first paragraph, the little detail that is misplaced in our story is that the time delay is not present. Our colonist clicks on the link to a server which is somewhere on Earth and the download is performed in no time.

 

For someone who has a basic understanding of protocol stacks (i.e. HTTP/TCP/IP), it is obvious that it would take quite some time to download a file from a server located on Earth to our Mars colony. All of a sudden, the ACK packets have lost their charm.

 

No reason to worry. Even if Mars outposts are far in the future, time and effort is spent on finding solutions for such communication problems in the present. The challenges seem overwhelming: very long delays, possible communication disruptions, and significant loss due to big bit error rates. A leap is necessary. The present protocols and architecture on which Internet relays have been designed assuming continuous and bi-directional paths, short round-trip times, and small error-rates.

 

One architecture that promises to solve the problems inherent to our scenario is the Delay Tolerant Networking (DTN) architecture, proposed in RFC 4838. A physical architecture that could solve the problems mentioned above is also proposed by Takashi Iida (Tokyo Metropolitan University), Yoshinori Arimoto (National Institute of Information and Communications Technology), and Yoshiaki Suzuki (NEC Corporation). The architecture would include clusters of communication satellites in orbit around Earth and Mars and relay satellites located at the Lagrangian points L4 and L5 of the Sun-Earth system. The relay satellites would make communication between Earth and Mars possible even when Mars is behind the Sun. Just a smart placement of relay satellites does not do the trick. In order to increase the responsiveness of the network, mirroring of data is also necessary.

 

You can find more information about space data systems on The Consultative Committee for Space Data Systems website. Other good resources include The InterPlaNetary Internet Project, and The Delay Tolerant Networking Research Group.

 

 

  • Facebook
  • Google
  • Slashdot
  • Reddit
  • Live
  • TwitThis

 

Credits: NASA

 

Software is a key component of present-day aerospace systems. Increased reliability is required from operating systems that host critical software applications.

 

Wind River’s VxWorks is a real-time operating system that is widely used in the aerospace industry. Missions using VxWorks include the Mars Reconnaissance Orbiter, the Phoenix Mars Lander, the Deep Impact space probe, Spirit and Opportunity Mars Exploration Rovers, and Stardust.

 

Mike Deliman, Senior Engineering Specialist at Wind River Systems, answered a few questions related to the new VxWorks MILS Platform 2.0.

 

DJ: What is VxWorks MILS Platform 2.0?
Mike Deliman: VxWorks MILS Platform 2.0 is a platform for creating systems that are evaluatable to high levels of the Common Criteria / Evaluated Assurance Level scale. VxWorks MILS 2.0 separation kernel is currently under evaluation by NIAP labs to an EAL 6+ level. The VxWorks MILS 2.0 Platform contains a separation kernel and technology to allow you to create multi-partitioned software systems where each partition can be evaluated to handle multiple independent levels of security (MILS) or to handle multiple levels of security (MLS). The long-and-short of it is similar to a VxWorks 653 flight OS, you can use a VxWorks MILS 2 platform to design a single platform that is capable of replacing multiple legacy systems. In other words, like a VxWorks 653 flight system, you can create a single modern system to replace multiple legacy systems, reducing Space, Weight and Power (SWaP) requirements.

 

DJ: What is a separation kernel and how did the concept make its way into software development for the aerospace industry?
M.D.: Separation Kernels allow you to take a single modern high-powered CPU and use it to replace several legacy systems. There are many examples of separation kernels and paradigms for their use. ARINC 653 defines a time and memory-space partitioning paradigm, services, and an API that must be provided (the Application Executive, or APEX). We have a platform – VxWorks 653 – that implements the ARINC 653 APEX separation and API. Separation Technologies are becoming quite popular, many are called “Hypervisors”. There are many Hypervisors out in cyberspace, the “Type 1” Hypervisors can all be thought of as forms of separation kernels. The Aerospace industry is a prime target for separation technologies because of the need to reduce the “SWaP” factors.

 

DJ: How does the VxWorks MILS separation kernel improve the reliability of aerospace applications?
M.D.: The VxWorks MILS separation kernel could be used to allow a single satellite to fulfill multiple missions. For instance, there may be a number of sensors and experiments on board, some for civilian / educational interests, some for NASA, some for research entities, perhaps some for the USAF. A MILS kernel could be used to collect, encode, and steer data safely, providing assurance that the data will not be mixed until it is in a state deemed “safe” for mixing. A satellite running a MILS separation kernel to handle such data wrangling could combine and satisfy multiple mission masters. If I were to be asked to design such a system, I would most likely recommend a flight computer separate from the science computer. Even if the science and flight SW were to share a single CPU, the separation technology would help ensure that no problems on any science application could affect any of the other science applications or any flight applications. In this way the flight system would be protected from anomalous events in the science packages, and the overall system would benefit from improved reliability.

 

DJ: John Rushby introduced the concept of separation kernel in order to provide multilevel secure operation on general-purpose multi-user systems. Do software applications developed for the aerospace industry (and I have in mind software running on micro-controllers) have the level of complexity that would require a separation kernel?
M.D.: Concentrating on the micro-controller aspect, no, most single (federated) systems running one micro-controller (or even several) do not even need a 32-bit processor dedicated to their operation. However, with a proper separation kernel and time-sliced architecture, you could use one modern high-speed 32-bit CPU to control and monitor a large number of smaller systems, and ensure any faults occurring on those control-and-monitor loops are contained. And as noted above, in a system used to satisfy requirements of multiple masters (agencies), MILS-style data separation may be the only way to keep satellite weight within limits and provide the information assurance the agencies require.

 

DJ: What features make the VxWorks operating system reliable and secure?
M.D.: Focusing on the VxWorks family of operating systems and the VxWorks OS API, VxWorks has been used in millions of devices over more than two decades of service, in applications as simple as MP3 players and as complex as autonomous space exploring robots, and as life-critical as telerobotic surgeons. There is no way a software company could anticipate the wide range of use that our customers have dreamed up and implemented. The VxWorks family of OSes share a common ancestry of code and all can benefit from bugs discovered and fixed in any of the family line.
 
Focusing on the VxWorks MILS platform, the separation kernel was designed expressly in compliance with the SKPP (the Protection Profile for separation kernels), with a focus on controlling embedded applications that require some degree of real-time control.

 

DJ: What are the features that make VxWorks a real-time operating system?
M.D.: Determinism is king in the real-time world. The ability to react to events in the real world with a high degree of determinism is what gives VxWorks its hard real-time responsiveness. This hard-determinism is carried over into all of the VxWorks family line, including our separation kernels and VxWorks SMP.

 

DJ: What toolchain is shipped with VxWorks? What programming languages are supported by the toolchain?
M.D.: Depending on the VxWorks package, one or more toolchains may be supplied and supported. For the most part, various versions of the Wind River Complier (formerly “Diab”), and various versions of the Gnu tools are supplied / supported with VxWorks. For the VxWorks MILS 2 platform we use a couple of versions of the GNU tool chains, specially modified for the parts they are used to build.

 

DJ: What hardware is targeted by the platform? Is an actual board necessary for development of applications or is an emulated target environment available for software engineers?
M.D.: Specifically, chips we are targeting include the following:
– Freescale 8641D (CW VPX6-165)
– Freescale 8548 (Wind River SBC8548)
– Intel Core 2 Duo (Supermicro C2SBC-Q)
– Freescale P2020, P1011, P4080 (future)
– Intel Atom, Nehalem (future)
We currently support Simics as the only simulation environment available for the VxWorks MILS platform.

 

Wind River Systems was founded in Berkeley, California in 1981. Intel bought Wind River Systems for a reported $884 million in July 2009. VxWorks real-time operating system is one of the Wind River flagship products.

 

  • Facebook
  • Google
  • Slashdot
  • Reddit
  • Live
  • TwitThis
04-17-09

Delta II

Posted by

 

Credits: NASA/MSFC

 

Delta II is a space launch system operated by United Launch Alliance (ULA), which was initially built by McDonnell Douglas, and by Boeing Integrated Defense Systems after McDonnell Douglas merged with Boeing in 1997.

 

As any other early space launch system, it evolved from a ballistic missile. In the 1960s, the Thor intermediate-range ballistic missile was modified to become the Delta launch vehicle. In 1981, after being operated for 24 years, Delta production was halted due to a change in U.S. space policy. However, in 1986, after the Challenger accident, it was decided that the Space Shuttle fleet would not carry commercial payloads anymore, paving the way for the return of the Delta launch vehicle. Delta II had its maiden flight on February 14, 1989.

 

 

Delta II launch vehicle is 38.2 to 39 m long, with a diameter of 2.44 m, and a mass that can range from 151,700 to 231,870 kg, depending on configuration. Delta II can be configured with two or three stages.

 

Delta II can inject a payload having a mass of 2,700 to 6,100 kg in low Earth orbit (LEO). Payloads deployed to Geosynchronous Transfer Orbit (GTO) can have a mass from 900 to 2,170 kg.

 

The first stage, Thor/Delta XLT-C, is powered by one Pratt & Whitney Rocketdyne RS-27A liquid fuel engine. The RS-27A engine is fueled by RP-1 and liquid oxygen. The RS-27A engine provides around 1,000 kN of thrust.

 

Credits: NASA

 

The solid boosters are used to increase the thrust of the launch vehicle. The first solid boosters used by Delta II 6000 series were Castor 4A motors. The 7000 and 7000 Heavy series use GEM 40 and GEM 46 solid motors respectively. The increase in thrust from Castor 4A to GEM 46 is substantial, from 480 kN to 630 kN.

 

Stage two, Delta K, is powered by a hypergolic restartable Aerojet AJ10-118K engine that can provide 43 kN. The AJ10-118K can fire more than once in order to insert the payload into LEO. The engine uses dinitrogen tetroxide as oxidizer and aerozine 50 (which is a mix of hydrazine and unsymmetrical dimethylhydrazine) as fuel. Besides having hard to pronounce names, the oxidizer and the fuel are very toxic and corrosive. The second stage contains the flight control system, which is a combined inertial system and guidance system.

 

 

The third stage, if present in the configuration, is a Payload Assist Module (PAM). This stage is powered by an ATK-Thiokol motor, which provides the velocity change needed for missions beyond Earth orbit. The stage has no active guidance control and it is spin-stabilized.

 

The de-spin mechanism used to slow the spin of the spacecraft after the burn and before the stage separation is a yo-yo de-spin mechanism. This mechanism consists of two cables with weights on the ends. The weights are released and the angular momentum transferred from the stage reduces the spin to a value that can be controlled by the attitude control system of the spacecraft.

 

Delta II can launch single, dual, or multiple payloads during the same mission. There are three fairing sizes available: composite 3-meter diameter, aluminum 2.9-meter diameter, and stretched composite 3-meter diameter.

 

Credits: NASA

 

Delta II is assembled on the launch pad. After hoisting the first stage into position, the solid boosters are hoisted and mated with the first stage. The second stage is then hoisted atop the first stage.

 

Delta II launch vehicles have a four-digit naming system. The first digit can be either 6 or 7, designating the 6000 or 7000 series. The second digit indicates the number of solid boosters used for the mission. Delta II can have three, four, or nine solid boosters strapped to the first stage. The third digit denotes the engine type used for the second stage. This digit is two for 6000 and 7000 series Delta II, which indicates the Aerojet A10 engine. The last digit designates the type of the third stage. Zero means that no third stage is used, whereas five indicates a third stage powered by a Star 48B solid motor, and 6 marks a third stage powered by a Star 37FM motor. A Delta II 7426 has 4 solid boosters and a third stage powered by a Star 37FM motor.

 

Delta II proved to be a very reliable Expendable Launch Vehicle (ELV). Some NASA missions that used Delta II as launch vehicle include: Mars Global Surveyor, Mars Pathfinder, Mars Exploration Rovers (MER-A Spirit and MER-B Opportunity), Mars Phoenix Lander, Dawn, STEREO, and Kepler.

 

After long years of service, Delta II is getting close to retirement. The final mission for Delta II is currently scheduled for 2011.

 

You can find more information about the Delta launch vehicles on the Delta web page on Boeing’s web site.

 

  • Facebook
  • Google
  • Slashdot
  • Reddit
  • Live
  • TwitThis

 

Credits: NASA

 

On January 3, 2004, the MER-A rover a.k.a. Spirit landed on Mars at the Gusev Crater. The second rover, MER-B a.k.a. Opportunity, followed twenty-one days later and landed at the Meridiani Planum.

 

They were both designed to operate for three months on the surface of Mars. Five years later, they are still operational and NASA has planned new missions for them.

 

 

Considering the harsh conditions on Mars, NASA’s twin rovers have accomplished remarkable things: they have returned a quarter-million images, driven more than thirteen miles, climbed a mountain, descended into impact craters, and survived dust storms. Using the Mars Odyssey orbiter as a communication relay, the rovers have sent more than 36 GB of scientific data back to Earth.

 

“These rovers are incredibly resilient considering the extreme environment the hardware experiences every day,” said John Callas, JPL project manager for Spirit and Opportunity. “We realize that a major rover component on either vehicle could fail at any time and end a mission with no advance notice, but on the other hand, we could accomplish the equivalent duration of four more prime missions on each rover in the year ahead.”

 

Credits: NASA

 

Digging into the MER mission archive, one detail caught my eye. The rovers carry plaques commemorating the crews of Columbia and Challenger, and some of the landmarks surrounding the landing sites of the rovers are dedicated to the astronauts of Apollo 1, Columbia, and Challenger.

 

Spirit is carrying a plaque commemorating the STS-107 Space Shuttle Columbia crew, which has been mounted on the high-gain antenna of the rover.

 

 

The names of the STS-107 crew are inscribed on the plaque: Rick D. Husband, William C. McCool, Michael P. Anderson, Kalpana Chawla, David M. Brown, Laurel B. Clark, and Ilan Ramon. Their names are now looking over the Martian landscapes.

 

To further honor their memory, the landing site of the MER Spirit is called the Columbia Memorial Station.

 

Credits: NASA

 

Three of the hills surrounding the Columbia Memorial Station are dedicated to the Apollo 1 crew: Gus Grissom, Ed White, and Roger Chafee. Grissom Hill is located 7.5 km to the southwest of Columbia Memorial Station, White Hill is 11.2 km northwest of the landing site, and Chafee Hill is located 14.3 km south-southwest of the landing site.

 

 

The area where Opportunity landed in the Meridiani Planum is called Challenger Memorial Station, in memory of the last crew of the Space Shuttle Challenger: Francis R. Scobee, Michael J. Smith, Judith A. Resnik, Ellison S. Onizuka, Ronald E. McNair, Gregory B. Jarvis, and Sharon Christa McAuliffe. I remember that Sharon Christa McAuliffe was NASA’s first teacher in space.

 

“The journeys have been motivated by science, but have led to something else important,” said Steve Squyres of Cornell University, in Ithaca, N.Y. Squyres is principal investigator for the rover science instruments. “This has turned into humanity’s first overland expedition on another planet. When people look back on this period of Mars exploration decades from now, Spirit and Opportunity may be considered most significant not for the science they accomplished, but for the first time we truly went exploring across the surface of Mars.”

 

  • Facebook
  • Google
  • Slashdot
  • Reddit
  • Live
  • TwitThis