3D printing for large space structures has gotten considerable press recently, following a press conference by startup company Deep Space Industries. Unnoticed by the press is Tethers Unlimited, a small company in Bothell, Washington that’s already working on a 3D printer for large space structures.

Tethers Unlimited has received a $100,000 grant from the NASA Institute of Advanced Concepts to begin development of the technology, which the company calls Spiderfab.

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Astrobotic Technology, Inc. and Carnegie Mellon University have received NASA funding to begin work on Spelunker, a prototype mission concept to explore a lunar cave.

Although the Moon has never had running water, which is responsible for most caves on Earth, it does have volcanic caves called lava tubes. In some locations, these tubes have partially collapsed to form openings called skylights. The Spelunker mission calls for landing on the rim of a skylight, followed by tethered descent of a power/communications hub and multiple robots. The robots would explore the interior of the cave using a combination of driving and hopping.

Right now, Spelunker is funded by a $498,411 Phase II grant from the NASA Institute of Advanced Concepts. Phase II studies will address the feasibility of skylight access, robot configurations for in-cave mobility and subsurface sensing, terrain modeling in darkness from a lightweight mobile platform, and autonomous exploration with hopping robots.

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The Kessler Syndrome refers to a potential nightmare scenario for orbital debris. If the density of objects in Low Earth Orbit  becomes high enough, a single collision could trigger a runaway cascade of additional collisions. The result would be a density of debris that renders Low Earth Orbit unusable for an extended period of time.

The Kessler Syndrome is named after NASA scientist Donald Kessler, who first pointed out the danger back in 1978? In 2009, Kessler wrote a paper on the  significance of the Kessler Syndrome today.

In that paper, Kessler stated the following:

We are entering a new era of debris control…. an era that will be dominated by a slowly increasing number of random catastrophic collisions.   These collisions will continue in the 800 km to 1000 km altitude regions, but will eventually spread to other regions.  The control of future debris requires, at a minimum, that we not leave future payloads and rocket bodies in orbit after their useful life and might require that we plan launches to return some objects already in orbit. 

Emphasis is per the original.

This statement has interesting implications for future space launch. If the key to avoiding the Kessler effect is not leaving rocket components in orbit, the use of expendable launch vehicles  is contraindicated and should be replaced with reusable launch systems as soon as possible.

Some independent thoughts about suborbital markets on the Fourth of July.

Tuesday night we watched the Kaboomtown fireworks show at Addison Airport. The ground-launch fireworks were impressive (it’s rated as one of the top five pyrotechnic displays in the United States, according the Travel Channel), but we noticed the greatest reaction at the start of the show, when fireworks were launched from a B-24 flying above the field.

At least, we believe it was the B-24. It was too dark to clearly discern the outlines of the aircraft, and there were no loudspeakers in our area to provide narration.

This led us to think about the possibility that someday, in the not too distant future, we might see fireworks launched from a suborbital spacecraft, and to muse on the form such a display might take.

The most practical display might not be actual fireworks at all. After all, fireworks explosions 50 miles up would be quite small as viewed from the ground, and there would be “boom” at all. Not very much fun. But in the past, scientists have used sounding rockets to create artificial auroras by releasing trimethyl aluminum into the upper atmosphere or exciting the upper atmosphere with electron beams. An artificial aurora might be an interesting complement to a ground-based fireworks show. Of course, the suborbital spacecraft could also launch fireworks on the way up or on the way down, while still close enough to the ground for an effective display.

Fireworks might seem like a frivolous use of suborbital spaceflight, and certainly no one would go to the expensive of developing a spacecraft for this purpose. But once suborbital spacecraft exist, operators will no doubt find all sorts of niche applications and customers like this.

Of course, this type of entertainment display requires a suborbital spacecraft that’s capable of launching and landing at night. The suborbital spacecraft now under development are designed for operation under daytime VFR conditions. There’s no point in adding the complexities of night-time and all-weather operation at this time. Once suborbital spacecraft are flying on a regular basis, though, it’s only a matter of time before someone decides to do the extra development of the avionics and procedures required for night operations. (There will be scientific payloads that want to fly at night as well.) Perhaps the NASA Flight Opportunities program, which has been funding enhancements to suborbital vehicles for scientific missions, will decide to take an interest at some point.