The local chapter of the American Institute of Aeronautics and Astronautics hosted a luncheon today with John Dankanich, the iSAT program manager as speaker. iSAT stands for Iodine Satellite, and it is a Cubesat program to test iodine instead of xenon in a Hall thruster engine. Right now, there aren’t a lot of options for small satellite propulsion. Solid motors are one use only, liquid engines take a lot of weight and space, and hypergols will try to kill you. By letting the iodine sublimate, i.e. go directly from solid to gas, all you need is a little heat to turn on your engine.
This isn’t the kind of engine that will lift a payload from Earth to orbit, but it will allow orbit change, even inclination change. Dankanich spoke about the military uses, being able to put communication relays or observation satellites into the right orbit quickly, perhaps even a constellation. You could have a constellation of small, cheap satellites around the moon or Mars or Venus. As for myself, I was interested in the end-of-life uses for small satellites, to deorbit a spacecraft before it becomes space debris.
Another point in favor of iodine was the much lower pressure than the current xenon Hall thruster engines. It opens up the possibility of rapid-prototyping your tank and even a conformal design to fit in the available space. Iodine presents some challenges in terms of what materials it’s compatible with, but we ought to be able to handle that.
Busek thruster proposed for iSAT. Photo courtesy of NASA/iSAT’s Facebook page.
It was an interesting talk, and it sounds like they have hit the ground running with a lot of hardware ready to go or easily modified for this mission. I wish them a lot of success in the future.
If you’d like to follow iSAT’s progress, they are on Facebook at http://www.facebook.com/NASAisat .
A 1994 N.T.S.B. review of thirty-seven major accidents between 1978 and 1990 that involved airline crews found that in thirty-one cases faulty or inadequate monitoring were partly to blame. Nothing had failed; the crew had just neglected to properly monitor the controls.The period studied coincided with an era of increased cockpit automation, which was designed to save lives by eliminating the dangers related to human error. The supporting logic was the same in aviation as it was in other fields: humans are highly fallible; systems, much less so. Automation would prevent mistakes caused by inattention, fatigue, and other human shortcomings, and free people to think about big-picture issues and, therefore, make better strategic decisions. Yet, as automation has increased, human error has not gone away: it remains the leading cause of aviation accidents.
via The Hazards of Going on Autopilot – The New Yorker.
I don’t look to The New Yorker for aerospace articles, but I thought this one was interesting enough to share. I welcome comments from the pilots here on whether automation hurts or helps.
I’ve been swamped at work (so many projects that I currently have 13 different charge codes) and at home (sending Rocketboy off to college), so it took me getting the “your mailbox is over its size limit” to wade through my news and announcement emails. I was saddened to see the news that astronaut Steven Nagel had passed away after a long battle with cancer.
Nagel had the distinction of flying twice in the same year – 1985 – first as a mission specialist on STS-51G, then as a pilot on STS-61A. I do not know of any other astronaut that has done this. He was commander of STS-37 in 1991 and STS-55 in 1993. He flew on Columbia, Challenger, Discovery, and Atlantis, missing only Endeavour for the set.
I met him after STS-37, which launched the Compton Gamma Ray Observatory. STS-61A and STS-55 were the German Spacelab missions. STS-51G was before I started working for NASA, but it was an international crew with a French astronaut and a Saudi prince.
Nagel had a long and successful career. After leaving NASA, he taught aerospace engineering at the University of Missouri at Columbia. He is survived by his wife and fellow astronaut Linda Godwin and their two daughters.
Oh! I have slipped the surly bonds of Earth
And danced the skies on laughter-silvered wings;
Sunward I’ve climbed, and joined the tumbling mirth
Of sun-split clouds, — and done a hundred things
You have not dreamed of — wheeled and soared and swung
High in the sunlit silence. Hov’ring there,
I’ve chased the shouting wind along, and flung
My eager craft through footless halls of air.
Up, up the long, delirious burning blue
I’ve topped the wind-swept heights with easy grace
Where never lark, or ever eagle flew —
And, while with silent, lifting mind I’ve trod
The high untrespassed sanctity of space,
Put out my hand, and touched the face of God.
— John Gillespie Magee, Jr
The Space Launch System, the latest NASA rocket, reached what’s called KDP-C, or Key Decision Point-C. This means that the powers that be gave it the green light, which is a step farther than Ares or Heavy Lift Launch Vehicle or any of the rocket programs of the last 20 years have made. Components such as the core stage and the five-segment rocket booster have passed their critical design reviews, and Michoud has been producing barrel segments for the core stage.
So what’s next? ATK is getting ready for the first qualification motor test of the five-segment rocket booster. Sixteen R-25 engines are at Stennis, with one being readied for testing this fall. Orion’s first flight, Exploration Flight Test-1 is set to fly in December.
Onward and upward.
NASA press release here.
There are holes in Curiosity wheels. There have always been holes — the rover landed with twelve holes deliberately machined in each wheel to aid in rover navigation. But there are new holes now: punctures, fissures, and ghastly tears. The holes in Curiosity’s wheels have become a major concern to the mission, affecting every day of mission operations and the choice of path to Mount Sharp.
via Curiosity wheel damage: The problem and solutions | The Planetary Society.
One of the Saturn program greybeards would always talk about designing for the unknown unknowns. In this case, the Curiosity team designed the wheels to counteract some of the problems encountered by the Spirit and Opportunity rovers. What they didn’t know is how much damage would be done by fatigue and punctures. They didn’t know the rover would encounter ventifacts (wind-eroded pyramidal rocks) that are embedded in bedrock, so they don’t move as the wheels roll over them.
The good thing is that they’ve been checking the condition of the rover, they understand the cause, and they can adjust the drive path or drive backwards to minimize further damage. The designers for the next rover, Mars 2020 should take note.
[Principal investigator Dr. Luke] Roberson explained that, from time to time, during the Space Shuttle Program tracking down the precise location of a hydrogen leak was a difficult challenge. Liquid hydrogen is a lightweight and extremely powerful rocket propellant used extensively by NASA. Its characteristics also make it highly flammable and explosive, requiring close attention to avoid leaks…NASA enlisted the assistance of University of Central Florida in developing a pigment that would change color when exposed to hydrogen. Chemochromic materials respond to the exposure to different chemicals with a change in color due to a chemical reaction within the substance.
“After two years of research, the team at UCF came up with a pigment that could be added to a silicon caulk,” Roberson said. “While it worked well, the caulk eventually dried out. We were then successful in adding the pigment to an air-tight Teflon tape.”
The end result was the development of the innovative “Color Changing Materials for Hydrogen Detection…One of the first applications took place as the space shuttle Endeavour was being prepared for the STS-118 mission in the summer of 2007.
“There was a hydrogen leak on the OMBUU and Launch Pad 39A,” said Roberson. “It proved to be elusive and we thought the tape could help.” The OMBUU was the Orbiter Midbody Umbilical Unit, a horizontal access arm for servicing the mid-fuselage portion of the space shuttle at the launch pad. It was used for loading liquid hydrogen and liquid oxygen into the spacecraft’s fuel cells.
“Sensors were successful in identifying that there was a leak,” Roberson said. “The tape helped pinpoint the exact location.”The tape works by changing color from beige to high-contrast black in less than three minutes when concentrations as low as 0.1 percent are detected. This is well before reaching the explosive combustion threshold of about four percent. The pigment is completely passive requiring no power and is highly resistive to environmental factors including ultraviolet exposure, salt spray and humidity.
via Innovative Hydrogen Leak Detection Tape Earns Prestigious Award | NASA.
The article points out the potential uses for the chemical manufacturing and oil and gas industries. Nice to see more spinoffs from the Shuttle program.
I just finished “The Weed Agency” by National Review’s Jim Geraghty. It’s the 30-year story of a fictional agency created by Jimmy Carter and the true attempts over the years to cut spending. Sure, the Democrats are tax-and-spend, but the Republicans are only too willing to blink first in the budget battles. While it’s a little frustrating to read, knowing there’s billions of dollars wasted in the federal gov’t, there’s enough funny bits to keep you turning the pages.
The part that hit home for me was the young go-get-‘em employees bogged down in red tape and “It’s not my idea, so I don’t like it” attitudes, especially the part about setting up a website. My group set up its own website in the 90’s to show off our unique capabilities and try to bring in outside business. This was soon followed by, “You can’t do that, we need all our websites to look the same.” Okay, uniform website coming up. This was followed by, “You can’t do that, it’s not 508 compliant.” Okay, we did that. Next was, “You can’t do that, it’s technical information, and that has to be cleared the same as papers and presentations.” Okay, we filled out the forms and sent them up the management chain. We have to do this every time before we can change the website? Okay. Finally, the spambots and hackers found us, so we said screw this and took it down. Somewhere in there, our secretary went through months of training to learn how to code HTML. She thought web designer skills would be the fast track for a raise. They contracted out the official webpage support.
Next in the reading queue is “The Girls of Atomic City” by Denise Kiernan. I picked this up when I was in Oak Ridge earlier this month.
So what are you reading?