Dr. Tom Crouch Interview Transcript

Tom Crouch photo

Photograph of Skywatchdc Team members Uwa, Zhou, and Tyler with Dr. Tom Crouch

Please click on the link below to read the transcript of the first 10 minutes of Skywatchdc’s April 8, 2013 Interview with Dr. Tom Crouch, Senior Curator at the National Air and Space Museum, on the history of tethered balloon technology. Dr. Crouch provides a historical context to the use of hot air balloons and aerostats in surveillance.

Transcript of Interview with Dr. Tom Crouch


Poster Presentation

skywatchdc posterSkywatchdc presented our poster and our publicity materials–brochure and postcard–at a poster session open to the CCT Georgetown Community on April 18.  The team members answered questions on our materials and the JLENS aerostat.  It was a great opportunity to introduce people to the JLENS technology and make them aware of the upcoming deployment.  We anticipate that knowledge of the JLENS aerostat in the DC area will increase as the September deployment date approaches and Skywatchdc is prepared to meet the need for information.

We will be introducing a new series of blog posts, called Q&A’s, based on questions that were asked during the poster session.  Planned future topics include items similar in size to the JLENS, a comparison of aerostats versus drones, and the $450 million cost of the JLENS.  Please post any questions that you would like us to address in future blogs in the comment section below.

Skywatchdc Team with Poster

The Skywatchdc team with the official Skywatchdc poster
Man, Emily, Tyler, Zhou, Uwa

Skywatchdc Presentation

Today, Skywatchdc gave a seven-minute presentation to the CCT 506 professors and students on the details of the JLENS aerostat, its historical context, and the positive and negative aspects of its upcoming deployment to the Aberdeen Proving Ground.  We also answered a variety of questions from the audience.  In addition, we previewed our upcoming interview-based video with a special trailer-length version.  The following slides were used in the Skywatchdc presentation and the photograph shows the Skywatchdc team mid-presentation.

Skywatch Slide 1Skywatch Slide 2Skywatch Slide 3Skywatch Slide 4Skywatch Slide 5


Skywatchdc Team During the Presentation
Zhou, Emily, Tyler, Uwa, Man

What Exactly is an Aerostat?


Image from Raven Aerostar

Balloons. Blimps. Lighter-Than-Air aircrafts. Aerostats. There are many classifications of airborne devices  that have occupied the skies for a number of years. An article from the Journal of Aircraft titled “Analysis and Design of Robust Helium Aerostats” provides useful background information describing the physical properties of aerostats.

The technology of an aerostat is not new. However, with increased use through the U.S. military and defense-related organizations, the term has been receiving more attention. Essentially, an aerostat is a system of technologies that work together. Below is a detailed description of how this system works. Researchers Jonathan Miller and Meyer Nahon from McGill University in Quebec, Canada explain:

“A typical tethered aerostat system consists of a fabric envelope to contain the lifting gas, one or more tethers to moor the balloon to the ground, a flying harness to distribute the tether load over the aerostat, load patches to attach the flying harness to the envelope, and occasionally, a pressure-regulation system known as a ballonet.”  (p. 1147)

To “moor” simply means to fasten or secure. The term ‘tether’ is a synonym for rope or a cord that ties two objects together. Aerostats are usually either blimp-shaped or sphere-shaped. In the case of the JLENS technology, their aerostats are in the shape of blimps. Even though tethered aerostats are fixed by a secure cable, they still require the use of helium gas to retain buoyancy in the air.

Knowing the inner-workings of any  type of technology is useful even if one is not an expert in the field of science, engineering or computing. Providing a well-rounded technical and social evaluation of aerostats in general helps to better conceptualize the specific technology of JLENS.

Referenced material:

Miller, Jonathan I. and Meyer Nahon.  “Analysis and Design of Robust Helium Aerostats”, Journal  of Aircraft, Vol. 44, No.5 (2007), pp.1447-1458 http://arc.aiaa.org/doi/abs/10.2514/1.25627?journalCode=ja&&

President Lincoln: Inspirational Leader; JLENS Enthusiast?

Telegraph from Lowe’s Balloon, 1861
Image from the Smithsonian Air and Space Museum

As Skywatchdc learned in our interview with Smithsonian National Air and Space Museum  Senior Curator Tom Crouch, the United States Air Force was (in-effect) created with aerostats in mind. Professor Thaddeus Lowe demonstrated the new technology on June 16, 1861, when he flew a balloon 500 feet above the White House.

Much like JLENS blimps, which are tethered to the ground by data-transmission cables, Lowe’s balloon was connected to the ground by a telegraph cable, demonstrating the capability to survey and report critical combat operations data from a superior vantage point. The technology has changed, but the concept is the same.

President Lincoln was so excited by the result that he invited the inventor to spend the night as a White House guest.  In July of 1861, Lincoln penned a memo mentioning this new technology:

Will Lieut. Gen. Scott please see Professor Lowe once more about his balloon? A. Lincoln, July 25, 1861 (See an image of the letter on the Smithsonian’s website)

Lincoln green-lighted the project, commissioning inventor Thaddeus Lowe to create a balloon corps for the Union Army. The Confederate Army failed to ever successfully shoot down a Union Army Balloon.

The Military History of Aerostats

Observation Balloon

Lighter than air aircraft have been around for hundreds of years.  JLENS is only the latest iteration of this highly-effective surveillance technology. You may be surprised to learn that observation balloons and aerostats have been used in battle since the 1790s. Here’s a look at some of the combat operations where balloons, aerostats, and blimps have been used over the years:

Aerostat technology in combat operations has changed throughout history. It is hardly a novel idea: societal and technological advances have shaped this technology into what it is today.

Unforeseen Circumstances: What Causes Damage to Aerostats?

Image of JLENS from UAS Vision

Image of JLENS from UAS Vision

With the introduction of the JLENS Aerostat this September in the DMV region, it can be assumed many people will want to know not only how aerostats work, but also the possibilities of technical failures. The Advances in Space Research published a report in 2011 titled “Dynamic Simulation of Breakaway Characteristics of Tethered Aerostats.” Researchers on this project used scientific and computer-based models to pinpoint what can cause tethered aerostats to breakaway or become damaged.

The JLENS project will operate as a tethered aerostat. Typically, tethered aerostats are defined as ultra-light ballonet or blimp-like vehicles secured to the ground by a cable. Even though tethered aerostats are attached to a cable, a certain level of helium and buoyancy is required for constant stabilization.

The most commonly found factors relating to the disruption of aerostats’ work are weather effects and abrasion. Aerostats situated in higher altitudes are subject to more atmospheric pressure and abrasion from strong winds, precipitation, and risk of helium escaping the aerostat.

Since the JLENS aerostat will be 10,000 feet in the air, there may be some concern for external effects while this device is patrolling the skies. That’s why researchers rely on computer programs such as FORTRAN to simulate the conditions in which an aerostat can break away. The simulation can model an aerostat’s changes when ascending and descending, the pressure from altitude changes, and effects on the time span an aerostat stays in the air.

The type of  information gathered from FORTRAN-based simulations and other computer programs can be useful for not only the manufacturers of aerostats, but also the general public. Especially for objects that are intended to secure and eliminate risks, preparing for worst-case-scenarios or even understanding the best methods to manage aerostats is crucial.