OrbitalHub

ULA dixit:

“A United Launch Alliance (ULA) Delta II rocket carrying launch NASA’s Ice, Cloud and land Elevation Satellite-2 (ICESat-2) mission lifts off from Space Launch Complex-2 at Vandenberg Air Force Base, California, on September 15, 2018. ICESat-2 is the 155th and final launch of the Delta II rocket. From its origin as the launch vehicle for the first Global Positioning System (GPS) satellites to NASA’s Earth observing, science and interplanetary satellites including Mars rovers Spirit and Opportunity to vital commercial communication and imaging satellites, the Delta II rocket has truly earned its place in space history.”

Video Credit: ULA

Credits: NASA

Let us see how the areas mentioned in the previous Sustainability in LEO post are covered at national level in the United States.

The United States has implemented a space traffic management program in the form of the Joint Space Operations Center (JSpOC) of the U.S. Strategic Command at Vandenberg Air Force Base in California.

JSpOC conducts periodic conjunction assessments for all NASA programs and projects that operate maneuverable spacecraft in low Earth orbits (LEO) or in geosynchronous orbits (GEO). Depending on the mission, the conjunction assessments can be performed up to three times daily. If JSpOC identifies an object that is expected to come in the proximity of a NASA spacecraft, and the collision risk is high enough (for manned missions the minimal value accepted is 1 in 10,000, while for robotic missions the threshold is 1 in 1,000), a conjunction assessment alert message is sent to the mission control in order to have collision avoidance maneuver commands sent to the spacecraft. The alert messages contain the predicted time and distance at closest approach, as well as the uncertainty associated with the prediction.

The control of the creation of space debris is addressed by orbital debris mitigation standard practices in four major areas: normal operations, accidental explosions, safe flight profile and operational configuration, and post-mission disposal of space structures. There are also NASA standards and processes that aim at limiting the generation of orbital debris.

The commonly-adopted mitigation methods, which focus on minimization of space debris creation, will not preserve the near-Earth environment for the future generations. As a matter of fact, the debris population increase will be worse than predicted by LEGEND-generated models due to ongoing launch activities and unexpected (but possible) major breakups. Here is where active space debris environment remediation comes into play.

The active space debris environment remediation is mainly concerned with the removal of large objects from orbit. Such large objects are defunct spacecraft (i.e. communication satellites that exceeded their operational life), upper stages of launch vehicles, and other mission-related objects. The removal of large objects from orbit is known as Active Debris Removal (ADR). Several innovative concepts are under study. Among them, tethers used for momentum exchange or electro-dynamic drag force, aerodynamic drag, solar sails, and auxiliary propulsion units. LEGEND studies have revealed that ADR is a viable control method as long as an effective removal selection criterion based on mass and collision probability is used, and there are at least five objects removed from orbit every year. The electrodynamic tethers seem to lead the competition so far, as they have a low mass requirement and can remove spent or dysfunctional spacecraft from low Earth orbit rapidly and safely.

Re-entry in the Earth’s atmosphere of space mission related objects is an important aspect to be considered in this context. Even though no casualties or injuries have been reported so far being caused by components of re-entering spacecraft, fragments from space hardware pose a risk to human life and property on the ground. One big concern is caused by the fact that the point of impact from uncontrolled re-entries cannot be calculated exactly. The uncertainties are due to a large number of parameters that affect the trajectory and the heat of ablation of objects re-entering the atmosphere.

Credits: NASA/Kim Shiflett

On March 6, 2009, the Delta II launch vehicle carrying the Kepler spacecraft lifted off from Launch Complex 17-B at Cape Canaveral Air Force Station in Florida.

In May 2009, Kepler started to hunt for other Earth-like planets in our galaxy. The technique used by Kepler to discover exo-planets is called transits. The large field of view of the Kepler telescope simultaneously captures the light of a very large number of stars in the Cygnus and Lyra constellations.

Kepler scientists already announced the discovery of five exoplanets named Kepler 4b, 5b, 6b, 7b, and 8b. The data collected by Kepler was also used to detect the atmosphere of the HAT-P-7b giant gas planet.

Kepler is expected to be operational until at least November 2012. Scientists hope to discover exo-planets in the habitable zone of other stars. The habitable zone is a region around a star where water can exist in liquid form on the surface of a planet. You can find more information about Kepler on NASA’s Kepler Mission website.

Credits: NASA

The Gravity Recovery And Interior Laboratory (GRAIL) is a mission that will measure the lunar gravity field in unprecedented detail. The twin spacecraft will orbit the Moon in tandem and collect scientific data for several months.

The GRAIL mission will cost $375 million and launch in 2011 as part of NASA’s Discovery Program. The window for the launch is 26 days long and opens on September 8, 2011.

After a dual launch aboard a Delta II 2920-10, the spacecraft will spend three to four months cruising on a low-energy trans-lunar trajectory. The two spacecraft will orbit the moon on 50 km, near-circular polar orbits, with a spacecraft separation of 175 – 225 km. The science phase of the mission will take 90 days, and it will be followed by a 12-month science data analysis.

The technique used by GRAIL for collecting scientific data was also used for the Gravity Recovery And Climate Experiment (GRACE) mission, launched in 2002. Small changes in the distance that separates the two spacecraft are translated in variations of the lunar gravity field.

The GRAIL spacecraft are based on the Lockheed Martin XSS-11 bus. The XSS-11 (Experimental Small Satellite 11) is the result of research done at Lockheed Martin Space Systems in the field of agile and affordable micro-satellites. Interesting to mention here is that there were speculations that XSS-11 could also be used as the base for the development of a kinetic anti-satellite weapon (ASAT).

The spacecraft is a rectangular composite structure. Two non-articulated solar arrays and lithium ion battery provides power. The attitude control system, the power management system, and the telecommunications system are also inherited from the XSS-11 bus.

The payload consists of a Ka-band Lunar Gravity Ranging System (LGRS), which is derived from the instrument carried by the GRACE spacecraft.

The spacecraft flight operations will be conducted from Lockheed Martin’s Denver facility. Science Level 0 and 1 data processing will be done at Jet Propulsion Laboratory (JPL), Level 2 data processing at JPL, the Goddard Space Flight Center (GSFC) and the Massachusetts Institute of Technology (MIT). The final scientific data will be delivered by MIT.

While missions like the Lunar Reconnaissance Orbiter (LRO) will find safe landing sites, locate potential resources, and take measurements of the radiation environment of the lunar surface, GRAIL will explore the moon from crust to core, and determine the moon’s internal structure and evolution.

More information about GRAIL is available on the GRAIL mission page on MIT’s web site.

Credits: NASA/JPL

Wide-field Infrared Survey Explorer or WISE is a NASA-funded scientific research project that will provide an all-sky survey in the mid-infrared wavelength range.

WISE will collect data that will allow scientists to compile an all-sky infrared image atlas and catalogue of over 300 million infrared sources. WISE will be able to measure the diameters of more than 100,000 asteroids that glow in the mid-infrared, and make observations of the coldest and nearest stars, regions of new star and planet formation, and the structure of our own galaxy.

WISE will only operate for seven to thirteen months. WISE will explore the entire Universe from a 523×523 km, 97.4-inclined orbit above the ground. The spacecraft will orbit in a Sun-synchronous orbit, so the solar panel will always be pointed at the Sun.

The cryostat will run for thirteen months. After a one-month in-orbit checkout period, the telescope will operate for six months. An additional pass of the sky (that would take another six months) is possible, if funded to do so by NASA.

Credits: UCLA/JPL

The spacecraft is 2.85 m long, 2.0 m wide, and 1.73 m deep. The spacecraft does not carry propellant. The telescope will make all pointing adjustments using reaction wheels and torque rods. Star trackers, sun sensors, a magnetometer, and gyroscopes will be the sensors used by the attitude control subsystem. The TDRSS (Tracking and Data Relay Satellite System) satellites will relay commands and data with ground stations.

The field of view is 47 arc minutes and it comes from a small telescope diameter (only 40 cm) and large detector arrays. The telescope has four infrared sensitive detector arrays, 1024×1024 pixels each. For the near-infrared bands, there are Mercury-Cadmium-Telluride (MCT) detectors, while for the mid-infrared bands, Arsenic-doped Silicon (Si:As) detectors are used.

Credits: UCLA/JPL

The optics instruments have to be cooled to very low temperatures in order to lower noise detection. The MCT detectors operate at 32 K, while the Si:As detectors will be cooled to less than 8 K.

The WISE launch is scheduled for November 2009. WISE will launch aboard a Delta II launch vehicle from Vandenberg Air Force Base, in California.

The WISE team consists of UCLA (University of California at Los Angeles), JPL (Jet Propulsion Laboratory), SDL (Space Dynamics Labs in Utah), BATC (Ball Aerospace & Technology Corporation), IPAC (Infrared Processing and Analysis Center), and UCB (University of California at Berkeley).

For more information about the WISE mission, you can visit the WISE mission homepage at the Space Science Laboratory, University of California, Berkeley, website.

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.