SpaceX’s first West Coast booster landing on land

Last night, SpaceX’s SAOCOM 1A mission from Vandenberg AFB in California went off without a hitch. For all appearances, it was a routine satellite launch to a low polar orbit. The timing, just after sunset, made for some beautiful sights (or terrifying sights, depending on the viewer). The spacecraft and their exhaust gases were high enough to be illuminated by the sun, which was well over the horizon by launch time.

What caught my attention, however, was the return-to-launch-site (RTLS) booster landing. All previous RTLS landings have been on the US east coast, at SpaceX’s Cape Canaveral AFS LZ-1 landing pad, which is far removed from the launch pads SLC-40 and LC-39A at 9 km (5.6 mi) and 14.8 km (9.2 mi), respectively. The LZ-4 landing pad on the west coast, however, is relatively close to the launch pad, at only about 425 meters (1400 ft or about a quarter of a mile). SpaceX captured the difference beautifully in the photo below.



SpaceX’s SAOCOM 1A mission launches from SLC-4E, delivers a payload to orbit, and lands 425 meters to the west at LZ-4 (photo by SpaceX)

Launch photographer John Kraus (one of my personal favorites) captured a similarly dramatic photo from a different perspective, using a sound-activated camera:



SAOCOM 1A launch and landing, about 8 minutes and 1400 ft apart (photo by John Kraus)


The ability to land boosters back at the launch site is critical to quick turnaround and low-cost reusability of Falcon 9. Landing at sea requires waiting on the landing ship to return to port, loading onto a truck, and transport back to the launch site. SpaceX are working on the ability to reuse the same first stage booster within 24 hours of a launch.

You can see more great shots from last night’s mission, and many more on SpaceX’s Flickr account and John Kraus’ website. Congratulations to SpaceX on the christening of their new landing pad, and nice work to the photographer(s)!


Final launch of historic Delta II rocket this weekend

This weekend will see the final flight of the Delta II rocket, launching NASA’s ICESat-2 (Saturday, Sept. 15 at 05:46 Pacific/12:46 UTC) from Vandenberg AFB in California. You can watch this launch on ULA’s website.

To date, the Delta II has successfully launched 153 missions, with 1 spectacular failure (a GPS mission), and 1 partial failure. Over its lifetime, it has been a major workhorse in the US unmanned space program, as well as commercial space. Among other payloads, the Delta II rocket has launched:

Delta II was also involved in the story of Lottie Williams, the only person on record to have ever been hit by orbital space debris. In 1997, Lottie was walking in a park in Tulsa, Oklahoma when a twisted, charred, light piece of metal fell out of the sky, “tapped” her on the shoulder and fell to the ground. She was uninjured. Later analysis revealed the debris to be from the second stage of the Midcourse Space Experiment, a mission launched by (ironically?) the Ballistic Missile Defense Organization on a Delta II rocket.

ICESat-2 will be using the last complete Delta II rocket in the United Launch Alliance (ULA)’s inventory. Missions capable of being launched by the Delta II recently have been launched using other, more modern rocket types. ULA CEO Tory Bruno suggested that “most” of the parts to build a Delta II remain in inventory, raising the possibility of a museum display.

The retirement of the Delta II marks the end of the career of a record-setting workhorse. If successful, ICESat-2 will be the 100th consecutive mission success for Delta II. It has been an important force in US space exploration and commercial success. However, today, more modern and efficient rockets are taking over the stage. With more nations and companies with orbital capabilities than ever before, and innovators pushing the envelope of what is possible and driving down costs, a new global space era beckons.

Explosion and roof collapse at Chicago sewage treatment works

CHICAGO — Metropolitan Water Reclamation District (MWRD) officials this morning reported an “explosion” at the Calumet Water Reclamation Plant (WRP). A subsequent press release called the event, which occurred about 11 a.m., a “roof collapse”. A fire spokesman said that ten workers were removed from the building; two had been pinned or buried by debris. Fortunately, no deaths have been reported, with five of ten workers released from the hospital before the end of the day. The plant remains in operation. The cause is still under investigation.

I was curious about exactly what could have happened, so I have written what I learned here.

The building and process

MWRD called the building where the explosion may have occurred, or whose roof partially collapsed, the “sludge concentration” building.

The treatment process used in Chicago is called the “activated sludge” process. Part of this process involves returning some sludge (solids that settle out after microorganisms have eaten organics in the sewage) to the aeration tanks, to keep populations of those microorganisms healthy. “Sludge concentration,” according to my reading, refers to a part of the process that ensures the return activated sludge (RAS) contains the proper number of microorganisms for efficient operation. Also, more generally, it can refer to simple thickening, or water removal.

Below is an aerial photo of most of the plant (from Google Maps) with the extent of the roof damage outlined.


Based on my limited understanding of the plant itself, the twelve larger, round tanks at the north end of the plant should be primary clarifiers. These allow heavier solids and sediment to settle out.

The next step is the long, rectangular aeration tanks. Here, sewage is infused with air to increase dissolved oxygen (DO), encouraging the growth and reproduction of bacteria and other microorganisms, which consume organic materials in the sewage.

The dark, round tanks (and some square tanks on the west side) are secondary clarifier tanks. These allow solids (sludge) to settle out after the water passes through the aeration tanks. Sludge is scraped from the bottom of the clarifiers and sent to the next step of its process, while clear, clean water overflows the top of the tank and is returned to a waterway as effluent.

This is where my understanding gets foggy when it comes to sludge. Various sources I have read say that “sludge concentration” is basically a “thickening” process — the removal of water. Both return activated sludge (RAS) and waste activated sludge (WAS, sent to landfill or consumers of biosolids) go through some thickening process. The RAS needs to be regulated carefully in terms of the populations of microorganisms present, in order to correctly feed back to the beginning of the treatment process. My guess is that the covered clarifiers immediately to the west of the building where the incident occurred today are sludge concentration tanks. Covered tanks help reduce odors.

This helps explain why the plant is still online; the sludge concentration process is required to keep populations of microorganisms healthy. I think the covered tanks are part of the return sludge concentration process. Perhaps the building in question is where waste sludge is processed for removal, and not part of the return process. It does appear to have large doors for trucks, which might be required to remove the waste sludge.

If anyone has further insight, it would be most welcome!

UPDATE (2018-09-09): The return sludge isn’t concentrated or thickened at Calumet WRP. Rather, the concentration or thickening process is only used on waste sludge, to reduce mass and volume for transport.