The Dawn of Ion Engines

Ion thrusters are becoming a bigger and bigger part of modern satellite design. Over 100 geosynchronous Earth Orbit communication satellites are being kept in the desired locations in orbit using this revolutionary technology. This post is about its most amazing achievement to date, the Dawn Spacecraft. Just reported that it is at the end of its second extension of the mission it has a few records under its belt. It is the first spacecraft to orbit two different celestial bodies, and the first to orbit any object in the main asteroid belt between Mars and Jupiter. It is also a record breaker for electric speed. Travelling over 25,700 mph it is 2.7x faster than the previous fastest electric thrusted spacecraft. That is a comparable speed to the Delta 2 launch vehicle that got it to space in the first place.

Delta 2 launch
The Dawn spacecraft launching on a Delta 2 rocket from Cape Canaveral Air Force Station SLC 17 on Sept 27th, 2007. Credit: NASA/Tony Gray & Robert Murra

The Dawn mission was designed to study two large bodies in the main asteroid belt. This is to get a deeper insight into the formation of the solar system . It also has the added benefit of testing the ion drive in deep space for much longer than previous spacecraft. Ceres and Vesta are the two most massive bodies in the belt, and are also very useful protoplanets from a scientific standpoint. Ceres is an icy and cold dwarf planet whereas Vesta is a rocky and dry asteroid. Understanding these bodies can bridge the understanding of how the rocky planets and icy bodies of the solar system form. It could also show how some of the rocky planets can hold water/ice. In 2006 the International Astronomical Union (IAU) changed the definition of what a planet is, and introduced the term “dwarf planet”. This is the change that downgraded Pluto from its planet status, although that has been argued to be wrong by Dr. Phil Metzger in a recent paper. Ceres is classified as a dwarf planet. As Dawn arrived at Ceres a few months before New Horizons reached Pluto, Dawn was the first to study a dwarf planet.

Dawn prior to encapsulation at its launch pad on July 1, 2007. Credit: NASA/Amanda Diller

The ion engine is so efficient that without them a trip to just Vesta would need 10 times more propellant, a much larger spacecraft, and therefore a much larger launch vehicle (making it much more expensive). The ion propulsion system that it uses was first proven by Deep Space Mission 1, along with 11 other technologies. Dawn has three 30 cm diameter (12 inch) ion thrust units. They can move in two axis to allow for migration of the center of mass as the mission progresses. The attitude control system can also use the movable ion thrusters to control the attitude. The mission only needs two of the thrusters to complete the mission, the third being a spare. All three have been used at some point during the mission, one at a time. As of September 7th 2018 the spacecraft has spent 5.9 years with the ion thrusters on, which is about 54% of its total time in space. The thrust to its first orbit took 979 days, with the entire mission being over 2000 days. Deep Space 1’s mission in contrast lasted 678 days before the fuel ran out.

An artist’s impression of Dawn with its ion thrusters on. Credit: NASA

The thrusters work by using electrical charge to accelerate ions from xenon fuel to speeds 7-10 times that of chemical engines. The power level and the fuel feed can be adjusted to act like a throttle. The thruster is very thrifty with its fuel, using a minor 3.25 milligrams of xenon per second, roughly 280g per day, at maximum thrust. The spacecraft carried 425 kg (937 pounds) of xenon propellant at launch. Xenon is a great fuel source because it is chemically inert, easily stored in compact form. Plus the atoms are very heavy so they provide large thrust compared to other comparable candidate propellants. At launch on Earth the xenon was 1.5 times the density of water. At full thrust the ion engines produce a thrust of 91 mN, which is roughly the force needed to hold a small sheet of paper. Over time these minute forces add up and over the course of years can produce very large speeds. The electrical power is produced by two 8.3 m (27 ft) x 2.3 m (7.7 ft) solar arrays. Each 18 meter squared (25 yard squared) array is covered in 5,740 individual photo voltaic cells. They can convert 28% of the sun’s energy into useful electricity. If these panels were on Earth they would produce 10 kW of energy. Each of the panels are on gimbals that mean they can turn any time to face the sun. The spacecraft uses a nickel-hydrogen battery to charge up and power during dark points in the mission.

The dawn mission patch.  This logo represents the mission of the Dawn spacecraft. During its nearly decade-long mission, Dawn will study the asteroid Vesta and dwarf planet Ceres Credit: NASA.

Vesta was discovered on March 29th 1807 by astronomer Heinrich Wilhelm Olbers, and is named after the Roman virgin goddess of home and hearth. The Dawn mission uncovered many unique surface features of the protoplanet ,twice the area of California, that have intrigued scientists. Two colossal impact craters were found in the southern hemisphere, the 500 km (310 miles) wide Rheasilvia basin, and the older 400 km (250 miles) wide Veneneia crater. The combined view of these craters was apparent even to the Hubble telescope. Dawn showed that the Rheasilvia crater’s width is 95% of the width of Vesta (it’s not perfectly spherical) and is roughly 19 km (12 miles) deep. The central peak of the crater rises to 19-25 km (12-16 miles) high, and being more that 160 km (100 miles) wide, it competes with Mars’ Olympus Mons as the largest mountain in the solar system. The debris that was propelled away from Vesta during the impacts made up 1% of its mass, and is now beginning its journey through the solar system. These are known as Vestoids, ranging from sand and gravel all the way up to boulders and smaller asteroids. About 6% of all meteorites that land on Earth are a result of this impact.


The brave new world of 4 Vesta, courtesy of NASA’s Dawn spacecraft. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

Dawn mapped Vesta’s geology, composition, cratering record and more during its orbit. It also managed to determine the inner structure by measuring its gravitational field. The measurements were consistent with the presence of an iron core of around 225 km (140 miles), in agreement with the size predicted by
howardite-eucrite-diogenite (HED)-based differentiation models. The Dawn mission confirmed that Vesta is the parent body of the HED meteorites, by matching them with lab based measurements. These experiments measured the elemental composition of Vesta’s surface and its specific mineralogy. These results confirm that Vesta experienced pervasive, maybe even global melting, implying that differentiation may be a common history for large planetesimals that condensed before short-lived heat-producing radioactive elements decayed away. The pitted terrains and gullies were found in several young craters. This could be interpreted as evidence of volatile releases and transient water flow. Vesta’s composition is volatile-depleted, so these hydrated materials are likely exogenic (formed on the surface).

A colour coded topographic map from the Dawn mission of the giant asteroid Vesta. Credit: NASA/JPL

The first object ever discovered in the main asteroid belt was Ceres. Named after the Roman goddess of corn and harvest, it was discovered by Italian astronomer Father Giuseppe Piazzi in 1801. Initially classified as a planet, it was later classified as an asteroid as more objects were found in the same region. In recognition of its planet like properties (being very spherical) it was designated a dwarf planet in 2006 along with Pluto and Eris. Observed by the Hubble telescope between 2003 and 2004, it was shown to be nearly spherical, and approximately 940 km (585 miles) wide. Ceres makes up 35% of the mass of the main asteroid belt. Before Dawn there were plenty of signs of water on Ceres. First, its low density indicates that it is 25% ice by mass, which makes it the most water rich body in the inner solar system after Earth (in absolute amount of water). Also, using Hershel in 2012 and 2013, evidence of water vapor, probably produced by ice near the surface transforming from solid to gas (known as sublimating).

Dwarf planet Ceres is shown in these false-color renderings, which highlight differences in surface materials. Credit: NASA/JPL-CalTech/UCLA/MPS/DLR/IDA

Acquiring all the data it needed by the middle of 2016, Dawn measured its global shape, mean density, surface morphology, mineralogy, elemental composition, regional gravity and topography at exceeded resolutions. The imaging from the mission showed a heavily cratered surface with bright features. Often referred to as “bright spots” they are deposits of carbonates and other salts. Multiple measurements showed an abundance of ice at higher latitudes. However the retention of craters up to 275 km (170 miles) in diameter argue for a strong crust, with lots of hydrated salts, rocks and clathrates (molecules trapped in a cage of water molecules). Gravity and topography data also indicated that that Ceres’ internal density increases with depth. This is evidence for internal differentiation resulting from the separation of the dense rock from the low density water-rich phases in Ceres history. The rock settled to form an inner mantle overlain with a water-rich crust. This internal differentiation is typical of small planets like Ceres and Vesta that Sets them apart from asteroids.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on.

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Roundup: Parker Solar Probe Launch

Rocket flames
An awesome image of the Delta IV heavy launching from pad 37B. Credit: Aerojet Rocketdyne.

At 07:31 UTC on August the 12th 2018 the 10th ever Delta IV heavy vehicle launched the long awaited Parker Solar Probe from Cape Canaveral Space Launch Complex 37B. The Delta 4 Heavy launched PSP towards a heliocentric orbit. The mission aims to “touch the sun”, and to get as close to the sun as man has ever been. Getting as close as 3.9 million miles from the sun, that’s roughly 4% of the distance between the Earth and the Sun (roughly 93 million miles).

time lapse
A great timelapse of the Delta 4 heavy launching towards the sun. Credit: Marcus Cote.

The Parker Solar Probe was named after Dr Eugene Parker who discovered the solar winds in 1958. He was present at the launch at the Kennedy Space Centre, seeing the 685kg spacecraft lifted. The 7 year mission will make 24 elliptical orbits of the sun, and uses 7 flybys of Venus to drop the low point of the orbit. It will make the closest point of the orbit closer than any other man made object in heliocentric orbit. It will enter the sun’s “atmosphere”, a section known as the corona, the outermost part of the atmosphere. Protected by a 4.5 inch sunshield, it can withstand temperatures of 2500F (1377C). The aim is to understand how the sun can creates and evolves solar flares and solar winds. It is to understand how the highest energy particles that pass the Earth are formed. It is hoped that it will revolutionise our understanding of the sun, to help us develop and create technology here on Earth.

The rocket has three RS-68A boosters, with the outbound boosters cutting off at T+3 min 57 sec, the core then cut off a minute and a half later at T+5 min 36 sec. The Delta’s cryogenic first stage engine was RL10B-2, which began burning at T+5 min 55 sec, and stopped its first burn at T+10 min 37 sec. This burn entered the 3,044 kg load into a 168 km x 183 km x 28.38 deg parking orbit. The second burn started at T+22 min 25 sec, and ended at T+36 min 39 sec, accelerating it to C3 of 59 km2/sec2, roughly 5,300 m/s out of LEO. At this point the Probe was in solar orbit, the Star 4BV separated at T+37 min 9 sec, with it firing at T+37 min 29 sec. The burn ended a minute and a half later at T+38 min 58 sec, accelerating it to 8,750 m/s beyond LEO. The Parker Solar Probe separated four and a half minutes later. The orbits after this point become much more complicated to get to the prefered orbit touching the sun.

Engineers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, work on NASA’s Parker Solar Probe spacecraft. Parker Solar Probe will be the first-ever mission to fly directly through the Sun’s atmosphere. Photo & Caption Credit: NASA / JHU-APL

The Delta 380 was the first Cape Canaveral Delta to use the upgraded “common avionics” system for its flight controller. The rocket was shipped to the Cape over a year ago, with it being assembled in the SLC 37 HIF. The rocket was then rolled out to the pad in April 2018, and there was a wet dress rehearsal on June 2 and 6th. The initial date for launch was the day before, august 11th but it was scrubbed at T-1 min 55 sec. Some of the best images of these launches are now taken by amateurs. I usually post a few of the images, but this launch was different as most of those who placed their cameras just a few hundred feet from the rocket got very damaged equipment.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on.

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Delta II Launch Site Demolished

Delta II launch
The launch of the GRAIL mission from Launch Complex 17 by a Delta II. The final launch from SLC-17. Credit: NASA/Tom Farrar and Tony Gray

At 11:00 UTC on the 12th of July 2018 the two launch towers of Space Launch Complex 17 were demolished by controlled explosions. The crowd of onlookers cheered as the towers fell, and took some great images and videos of the demolition. The launch site had not been used since 2011 when Delta II 7920H-10C fired NASA’s GRAIL spacecraft towards the Moon. The launch complex had two pads named 17A and 17B. The site is now to be reused as a test bed for potential lunar landers made by Moon Express. Boasting some very prestigious missions well beyond Earth SLC-17 will be remembered as an important part of the history of American space.

Delta Echo 1
A delta Rocket carrying NASA’s Echo 1 satellite launching August 12th 1960. The Echo satellite inflated in orbit to reflect signals back to Earth. Credit: NASA.

It was built in 1956 for use as a launch site for the PGM-17 Thor missile. This was the first operational ballistic missile that the United States had in their arsenal. The first launch of a Thor missile from 17A was 3rd of August 1957, with the first launch from 17B being 25th of January 1957. In the early 1960s the site was upgraded to support a variety of Expendable Launch Vehicles, all of which were derived in some way from the Thor booster. We now know this family of rockets as the Delta rockets used by the United Launch Alliance. Thirty five early Delta rocket missions were launched from LC-17 between 1960 and 1965. At that point operated by the US Air Force. In 1965 the operation of the site was transferred to NASA.

View of LC-17
View of LC-17 viewing East. A fairly old photo taken by the U.S. Army Corps of Engineers. Credit: Martin Stupich

In 1988 the site was returned to the Air Force to support the Delta II program. The site had to be modified to facilitate the new more powerful rocket, with new platforms being installed and the D=Ground Service Tower was raised by 10 ft. The program entered service in 1989 after worries about the shuttle due to the Challenger disaster. Pad 17B was modified in 1997 to support a newer more powerful launch vehicle the Delta III which made its maiden flight on 26th of August 1998. Ending in failure, the next three attempts were failures in some sense and the programme was abandoned in late 2000. The Delta II continued to launch, with it’s fairly cheap price tag, and amazing track record it has been a favourite for NASA on a number of big projects. This post by NASA explains how the layout of the site and the small teams allowed LC-17 to be efficient and consistent over it’s 50 year lifespan. Some Delta II launches could be within days of each other because the launch crews were so effective.

Space Launch Complex 17
A view of Space Launch Complex 17, pads A and B taken in 2007. Delta II rocket with THEMIS aboard sits on Pad B. Credit: NASA/George Shelton

There have been some very famous spacecraft launched from SLC-17 in the years, mostly by Delta I and II rockets. Among them the Explorer and Pioneer space probes studying the physics of our solar system, and exploring some of it. All of the Orbiting Solar Observatories between 1962 and 1975 were launched from this site, as well as the Solar Maximum mission in 1980. Some of the first weather satellites like TIROS and later GOES were launched from SLC-17 allowing much better understanding of weather and improving (mainly military) weather reports. My personal favourite launches are those of the Mars Exploration Rovers in 2003. Both spirit and Opportunity (still going) were launched from this important launch site.

Spirit lifting off
A Delta II launching from pad SLC-17A with the MER-A or Spirit Rover towards Mars on June 10th 2003. Credit: NASA/KSC

Space Launch Complex 17 is also famous for being the last site where you had to press a button to launch the rocket. Most pads had a computerized auto-sequencer, much like the space shuttle, and in the modern world of rocketry it makes much more sense to do that. Even after 1995 when they got rid of the button (sadly) a human needed to press go on a computer to say launch. Bill Hodge, an electrical engineer at the launch complex said “If you didn’t push that button, it didn’t launch.” Tom Mahaney, project manager for the closeout of the complex described the site as “hectic, but not dysfunctional.” This is the best description I can find of this massively important historical site. In its time it has supported a total of 325 Thor and Delta rocket launches!

Thank you for reading, take a look at my other posts if you are interested in space or electronics, or follow me on Twitter to get updates on projects I am currently working on.


Atlas V Launches InSight

Atlas V on the pad
The Atlas V on the launch pad at vandenberg AFB in California, Credit: ULA flickr.

At 11:05 UTC on May 5th 2018 the forth Atlas launch of the year launched the long awaited InSight mission on a course for mars. Launching from Vandenberg Air Force Base the AV-078 (the launch designation) was an Atlas V in 401 configuration. It was the first interplanetary launch from the west coast of the United States. Liftoff of the Atlas V with a 4m payload fairing was from Space Launch Complex 3 East.

Sam Suns first tweet
An awesome photo of the launch that blew up on twitter, taken from the sky. Credit @BirdsNSpace on Twitter.

The rocket had one main payload, the InSight Mission and two CubeSats. InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) is a robotic lander designed to study the interior of the planet Mars.  I weighed 694 kg at launch, including a 425 kg fueled lander. The lander carries a probe that will be hammered 15m into the Mars surface, a seismometer, a magnetometer (first expected to land on the surface of Mars), a laser reflector, along with other instruments. The lander also has a robotic arm to move payloads around, but there will be another post in the future discussing the instruments in more detail. The two CubeSats on board are known as MarCO-A and MarCO-B, each weighing about 13.5 kg. They will fly by Mars while conducting a data relay experiment with InSight.

Insight Fairing
The 4m payload fairing on top of the Atlas V containing the InSight payload. Credit: ULA Flickr.

The design of InSight was developed from the 2008 Phoenix Mars Lander. The previous lander was launched on Delta 2 rockets compared to the Atlas V, both built and launched by the United Launch Alliance. The Atlas V does have excess capability for the mission (slightly overkill) but this allowed it to be launched from Vandenberg AFB. Previous solar orbit missions (like this one) were launched from the Cape to gain the site’s eastward earth rotational velocity. Vandenberg launches have to fly south or westerly direction across the Pacific Ocean. InSight was originally planned to launch in 2016 but was delayed to 2018 due to the main instrument failing.

Liftoff od Insight
The Atlas V lifts off, unfortunately the fog rolled in so very few great shots were taken by the remote cameras. Credit: ULA Flickr.

AV-078 started on a 158 degree azimuth, aiming towards a 63.4 degree Low Earth Parking Orbit. The LOX/RP-1 fueled RD-180 powered first stage fired for 4 minutes and 4 seconds. The Centaur’s RL10C-1 LOX/LH2 engine then fired for 8 minutes and 48 seconds to reach the parking orbit. It then coasted for 65 minutes and 40 seconds then performing a second, 5 minute and 23 second burn to accelerate into a trans-Mars solar orbit. Insight separated 9 minutes after at about T+1 hour, 33 minutes and 19 seconds. The CubeSats separated shortly after.

Aaron Colier Atlas V launch
An awesome long exposure shot of the launch taken by Aaron Collier. From roughly 85 miles away. Credit @aaroncollier96 on Twitter.

Atlas 5 Launches a Trio of Spy Satellites

Atlas 5 taking off
Atlas 5 lifting off from pad 41 at Cape Canaveral Air Force Base. Credit: @marcuscotephoto on Twitter

At 23.13 UTC on April 14th 2018 the third Atlas 5 launch of the year fired multiple military satellites into a near geosynchronous orbit. Launching from Space Launch Complex 41 at Cape Canaveral, FL,  the AV-079 (the launch designation) was an Atlas V in 551 configuration. The rocket had 5 solid rocket motors, a Centaur second stage powered by a single RL10C-1 LOX/LH2 engine, and a 5m diameter payload fairing. The entire mission lasted approximately 7 hours and is known as Air Force Space Command (AFSPC) 11 mission.

The Atlas 5 AFSPC11
The Atlas V carrying AFSPC11 for the Air Force Space Command. Credit: United Launch Alliance Flickr.
the smoke trail
A smoke trail left by the Atlas V as it launches a trio of spy satellites. Credit: @marcuscotephoto on twitter.

The mission lifted two primary satellites for the Air Force, one stacked on top of the other. On the top was CBAS (Continuous Broadcast Augmenting SATCOM) an abbreviation within an abbreviation, and a military communications satellite. The second satellite was named EAGLE (ESPA Augmented GEO Laboratory Experiment) which is an abbreviation with two abbreviations in it! This satellite is based on an Orbital ATK ESPA bus, it is a research laboratory that can host 6 deployable payloads. It is said that EAGLE likely weighed around 780 kg. There was also a subsatellite named “Mycroft” reported to be on the flight, but not confirmed.

The fury of the Atlas V
The fury of the 5 solid rocket boosters found on this Atlas V. Credit: United Launch Alliance Flickr.

The Solid motors finished their burn and seperated 1 minute and 47 seconds after liftoff. The first stage,  an RD-180 rocket fired for 4 minutes and 33.5 seconds. Centaur then performed 3 burns which were not shown on the livestream. The first burn was meant to last 6 minutes 1 seconds to reach a low earth parking orbit. The second burn began 12 minutes and 6 seconds after the first cutoff, and last 4 minutes and 49 seconds, putting the vehicle into a geosynchronous transfer orbit. After a 5 hour and 6 minute apogee, a third burn of 2 minutes and 36 seconds completed the insertion to the planned orbit. A spacecraft separation extended for another 1 and a half hours to T+6 hours 57 min 24 sec.

Atlas v launchpad
Atlas V rolling to the launchpad at Space Launch Complex 41 at Cape Canaveral AFB. Credit: United Launch Alliance Flickr.

To find similar photos, and to buy reasonably priced prints of some of the above visit www.marcuscotephotography.com

The Latest Atlas V Launch GOES-S Well

The Atlas V launch
The Atlas V launch taken by @marcuscotephoto on twitter.

At 22:02 UTC on March 1st 2018 the Second Atlas V launch of 2018 fired the 5,192kg GOES-S satellite into orbit. Launching from Space Launch Complex 41 at Cape Canaveral, FL, the AV-077 (the launch designation) was an Atlas V in 541  configuration. GOES-S, an A2100 series satellite built by Lockheed Martin, was separated 3.5 hours into the mission into a 8,215km x 35,286km x 9.52 deg Geosynchronous Transfer Orbit (GTO).

Atlas V launch
Atlas V launch from Launch Complex 41 at Cape Canaveral, FL. Image from @NOAASatellites Twitter.

The second of a new generation of weather satellites for the United States, GOES-S follows in the footsteps of GOES-East, now renamed to GOES-16. A huge jump in satellite capability, the new set of satellites cover from eastern Japan all the way over to west Africa, as well as parts of the Arctic and Antarctic. They can detect storms faster, see lightning and even have sensors to detect solar storms. The satellites were commissioned by the National Environmental Satellite, Data and Information Service (NESDIS) who manage the National Oceanographic and Atmospheric Administration (NOAA) constellation of environmental satellites. For more images and information follow them on twitter @NOAASatellites.

The new generation of weather satellites
Image showing the difference between GOES-16 and the previous version, GOES-13. Image from @NOASatellites twitter.

There are versions of the livestream on Youtube, and a highlight reel on the ULA Youtube page. They are definitely worth a watch if you want more information from the engineers themselves.

Atlas V launch
Atlas V launching the GOES-S satellite on March 1st 2018. Image from @NOAASatellites Twitter
The Atlas V just taking off
The Atlas V just taking off, Image from @NOAASatellites

To find similar photos, and to buy reasonably priced prints of some of the above visit www.marcuscotephotography.com