Juno Spacecraft Crosses Jupiter/Sun Gravity Boundary

NASA’s Juno Spacecraft Crosses Jupiter/Sun Gravitational Boundary

Scientia — Since its launch five years ago, there have been three forces tugging at NASA’s Juno spacecraft as it speeds through the solar system. The sun, Earth and Jupiter have all been influential — a gravitational trifecta of sorts. At times, Earth was close enough to be the frontrunner. More recently, the sun has had the most clout when it comes to Juno’s trajectory. Today, it can be reported that Jupiter is now in the gravitational driver’s seat, and the basketball court-sized spacecraft is not looking back.

This artist’s rendering shows NASA’s Juno spacecraft making one of its close passes over Jupiter.
Credits: NASA/JPL-Caltech

“Today the gravitational influence of Jupiter is neck and neck with that of the sun,” said Rick Nybakken, Juno project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “As of tomorrow, and for the rest of the mission, we project Jupiter’s gravity will dominate as the trajectory-perturbing effects by other celestial bodies are reduced to insignificant roles.”

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Juno was launched on Aug. 5, 2011. On July 4 of this year, it will perform a Jupiter orbit insertion maneuver — a 35-minute burn of its main engine, which will impart a mean change in velocity of 1,212 mph (542 meters per second) on the spacecraft. Once in orbit, the spacecraft will circle the Jovian world 37 times, skimming to within 3,100 miles (5,000 kilometers) above the planet’s cloud tops. During the flybys, Juno will probe beneath the obscuring cloud cover of Jupiter and study its auroras to learn more about the planet’s origins, structure, atmosphere and magnetosphere.

Juno’s name comes from Greek and Roman mythology. The mythical god Jupiter drew a veil of clouds around himself to hide his mischief, and his wife — the goddess Juno — was able to peer through the clouds and reveal Jupiter’s true nature.

NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for NASA’s Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. The California Institute of Technology in Pasadena manages JPL for NASA.

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– Credit and Resource –

NASA

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Juno Spacecraft Crosses Jupiter/Sun Gravity Boundary

Cassini"s Enceladus Final Flyby

Scientia — In late 2015, NASA’s Cassini spacecraft is making its final three flybys of Enceladus, the little moon that stunned scientists with the revelation it harbors a global ocean under its icy shell, active geysers of water-ice feeding one of Saturn’s rings and the first tantalizing signs of hydrothermal activity beyond Earth. All these discoveries have vaulted Enceladus to one of the top future destinations for exploration and the search for signs of potential life beyond Earth.

• 14 October 2015: Cassini aligned it self to get some of the best shots of Saturn’s Moon Enceladus. Cassini was looking at the moon’s north polar region at an altitude of just 1,142 miles (1,839 kilometers).
  
  

  This high-resolution Cassini image shows a landscape of stark contrasts on Saturn’s moon Enceladus. Thin cracks cross over the pole — the northernmost extent of a global system of such fractures. Credit: NASA/JPL/Space Science Institute – Provided by NASA

  
  
  Scientists expected the north polar region of Enceladus to be heavily cratered, based on low-resolution images from the Voyager mission, but the new high-resolution Cassini images show a landscape of stark contrasts. “The northern regions are crisscrossed by a spidery network of gossamer-thin cracks that slice through the craters,” said Paul Helfenstein, a member of the Cassini imaging team at Cornell University, Ithaca, New York. “These thin cracks are ubiquitous on Enceladus, and now we see that they extend across the northern terrains as well.”
  
  
  
  



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  28 October 2015: Cassini will make a daring flight through the moon’s famous plume only 30 miles (48 kilometers) above Enceladus’ south pole. The flyby is Cassini’s deepest-ever dive through the jets. The encounter will allow Cassini to obtain the most accurate measurements yet of the plume’s composition, and new insights into the ocean world beneath the ice.
  

  NASA’s Cassini spacecraft will sample the ocean of Saturn’s moon Enceladus on Wednesday, Oct. 28, when it flies through the moon’s plume of icy spray.

  
  

  Cassini launched in 1997 and entered orbit around Saturn in 2004. Since then, it has been studying the huge planet, its rings and its magnetic field. Here are some things to know about the mission’s upcoming close flyby of Enceladus:

  
  
  1. Enceladus is an icy moon of Saturn. Early in its mission, Cassini discovered Enceladus has remarkable geologic activity, including a towering plume of ice, water vapor and organic molecules spraying from its south polar region. Cassini later determined the moon has a global ocean and likely hydrothermal activity, meaning it could have the ingredients needed to support simple life.
  
  
  2. The flyby will be Cassini’s deepest-ever dive through the Enceladus plume, which is thought to come from the ocean below. The spacecraft has flown closer to the surface of Enceladus before, but never this low directly through the active plume.
  
  
  3. The flyby is not intended to detect life, but it will provide powerful new insights about how habitable the ocean environment is within Enceladus.
  
  
  4. Cassini scientists are hopeful the flyby will provide insights about how much hydrothermal activity — that is, chemistry involving rock and hot water — is occurring within Enceladus. This activity could have important implications for the potential habitability of the ocean for simple forms of life. The critical measurement for these questions is the detection of molecular hydrogen by the spacecraft.
  
  
  5. Scientists also expect to better understand the chemistry of the plume as a result of the flyby. The low altitude of the encounter is, in part, intended to afford Cassini greater sensitivity to heavier, more massive molecules, including organics, than the spacecraft has observed during previous, higher-altitude passes through the plume.
  
  
  6. The flyby will help solve the mystery of whether the plume is composed of column-like, individual jets, or sinuous, icy curtain eruptions — or a combination of both. The answer would make clearer how material is getting to the surface from the ocean below.
  
  
  7. Researchers are not sure how much icy material the plumes are actually spraying into space. The amount of activity has major implications for how long Enceladus might have been active.
  
  
  
  


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  19 December 2015: Cassini’s final targeted flyby will allow the spacecraft to measure heat flow from the moon’s interior at an altitude of 3,106 miles, or 4,999 kilometers.

  
  
  
  

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– Credit and Resource –

NASA

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Cassini"s Enceladus Final Flyby

New Green Propellants Complete Milestones

Scientia — To stay in the proper orbit, many satellites have thrusters–small rocket engines–that fire to change altitude or orientation in space. On Earth where gravity dominates, 5 pounds of thrust, equivalent to 22 Newtons of force, may seem small, but in space, it doesn’t take much thrust to move a large spacecraft.

Currently, most satellite thrusters are powered by hydrazine, a toxic and corrosive fuel that is dangerous to handle and store. In a quest to replace hydrazine with a more environmentally friendly fuel, NASA is testing thrusters propelled by green propellants that can provide better performance than hydrazine without the toxicity. These propellants could help lower costs by eliminating infrastructure needed for handling toxic fuels and reducing processing time–making it less expensive and safer and easier to launch both commercial and NASA spacecraft.

This image reveals a temperature profile of a 22 Newton thruster using the green propellant LMP-103S during a 10-second pulsing test that ratchets the temperature upward. Using this data, engineers can determine how chemical reactions cause heat to flow around to the thruster over time.
Credits: NASA/MSFC/Christopher Burnside

“When you consider all of the satellites in orbit today that do everything from observing Earth and monitoring weather to peering deep into our universe to answer questions about its origins, it’s easy to see that using green propellants will make a big difference in increased mission performance at a reduced cost while keeping both the environment and our workforce safe from contamination,” said Steve Jurczyk, NASA’s associate administrator for the Space Technology Mission Directorate (STMD) at NASA Headquarters in Washington. “NASA has a rich history of ensuring our technology and scientific prowess has a benefit to life on Earth, and green propellant will help ensure that NASA continues to be a steward of this planet.”

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NASA recently completed several hot-fire tests with thrusters powered by two different green propellants with the potential to replace hydrazine. Both are ionic liquid-based blends that are less toxic and less flammable than hydrazine, which makes them easier and less costly to store, to handle and to fuel up spacecraft before launch. Additionally, the new propellants offer higher performance, delivering more thrust for a given quantity of propellant than hydrazine.

NASA engineers monitor temperature data on the left computer screen as a thruster fueled with the green propellant LMP-103S viewed on the right computer screen is fired at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
Credits: NASA/MSFC/Fred Deaton

One of the green propellants is a hydroxylammonium nitrate-based propellant known as AF-M315E. It was developed by the Air Force Research Laboratory at Edwards Air Force Base in California. This propellant will be demonstrated on a small satellite on NASA’s Green Propellant Infusion Mission (GPIM). During the GPIM flight, the smallsat will fire thrusters powered by AF-M315E to conduct maneuvers to change the satellite’s altitude and orientation. GPIM recently passed a major milestone with the delivery of the propellant’s propulsion subsystem built by Aerojet Rocketdyne in Redmond, Washington, to the mission’s prime contractor, Ball Aerospace & Technologies Corp. in Boulder, Colorado, for integration into the spacecraft. For this project, the GPIM team tested two different sized thrusters (1 and 22 Newton) with AF-M315E. Five of the 1-Newton thrusters will fly on GPIM.

“With GPIM’s flight scheduled to launch next year, NASA and the aerospace industry have taken positive steps to demonstrate use of a propellant that will reduce satellite fueling hazards and save time and money during launch campaigns,” said Tim Smith, GPIM mission manager for NASA’s Technology Demonstration Missions at Marshall. GPIM is managed by STMD’s Technology Demonstration Missions Program Office at Marshall.

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The other green propellant is a fuel called LMP-103S, which is based on the oxidizer ammonium dinitramide produced by Eurenco Bofors in Karlskoga, Sweden. A team at NASA’s Marshall Space Flight Center in Huntsville, Alabama, recently completed tests with both 5 Newton and 22 Newton thruster built by ECAPS and powered by LMP-103S. Engineers fired the 22 Newton thruster 35 times under varying conditions and monitored results with infrared cameras. Orbital ATK, Inc. assisted NASA with these tests.

Large and small thrusters are used to propel satellites in space. NASA engineers conducted the first tests with a 22 Newton (5-pound) thruster fueled with the green propellant LMP-103S. Engineer Chris Burnside examines a smaller 5 Newton (1-pound) thruster that also was tested at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
Credits: NASA/MSFC/Fred Deaton

“We conducted the first NASA tests with 22 Newton thrusters with this propellant in the United States,” said Christopher Burnside, lead engineer for testing the LMP-103S propellant. “They performed quite well, providing performance at comparable levels to today’s hydrazine thrusters. It’s always great to put thrusters through the paces in an environment that simulates operational conditions.”

To guide future investments, NASA is leading the development of a green propellant roadmap along with other government agencies, industry and academic leaders who recently shared their collective experiences during a technical interchange meeting at Marshall.

“I like the analogy of relating thrusters and propellant systems to aircraft,” said Charles Pierce, manager of Marshall’s Spacecraft Propulsion Systems Branch, which recently completed the tests with LMP-103S. “One aircraft doesn’t meet every need. Some high performance aircraft need to fly fast while other larger aircraft need to conserve fuel and fly slowly. Some carry passengers while others carry only cargo. Likewise, NASA needs to have flexibility in the types of thrusters and propellant systems it has to meet a variety of mission needs. One type of propellant might work best for one type of mission while another is better suited for a different mission. It’s important that we have choices as we go green.”

– Credit and Resource –

Tracy McMahan

NASA Marshall Space Flight Center

256-544-0034

tracy.mcmahan@nasa.gov

Last Updated: Sep. 14, 2015

Editor: Lee Mohon

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New Green Propellants Complete Milestones