Sandia Labs/Scaled Composites Su-25 ROAR (Rocket-On-A-Rope)


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25 June 2009
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The provides this piece of Rutan mystery in his biography:

SU25 1/4 scale ROAR
Sandia National Laboratories
Apr 91
Scaled Composites
rocket powered cable-mounted decoy

After researching this long and hard (which, from my European standpoint, not being near any of the real archives, amounts to using the web, sorry for all those who will call me a "lounge researcher"!) and after being sidetracked for a while into researching the Sukhoi Su-25 scale RPVT decoys by mistake (!) I have finally found some stuff on this little-known program:

"A high-velocity impact testing technique, utilizing a tethered rocket, is being developed at Sandia National Laboratories. The technique involves tethering a rocket assembly to a pivot location and flying it in a semicircular trajectory to deliver the rocket and payload to an impact target location. Integral to developing this testing technique is the parallel development of accurate simulation models. An operational computer code, called ROAR (Rocket-on-a-Rope), has been developed to simulate the three-dimensional transient dynamic behavior of the tether and motor/payload assembly. This report presents a discussion of the parameters modeled, the governing set of equations, the through-time integration scheme, and the input required to set up a model. Also included is a sample problem and a comparison with experimental results."

from ROAR: A 3-D tethered rocket simulation code by A. R. York, II and J. S. Ludwigsen
Affiliation: Sandia National Labs., Albuquerque, NM.
Publication Date: 04/1992
Category: Spacecraft Propulsion and Power

"The Supersonic Rocket-on-a-Rope (SROAR) test method was developed as a low-cost and high-fidelity
alternative to sled testing. This method utilizes hightensioned ropes to deliver a payload directly to a desired target, at which point the ropes are terminated. The test missile flies on the ropes to a precise hit-point controlled by the location of the rope anchors. Trajectory, angle of attack, velocity, and impact obliquity can all be controlled by rope length, rope tension and target placement.
The basic concept of SROAR is not original in that several test facilities have used this technology for
conducting controlled flights of several payloads. These facilities include Sandia National Laboratories dating back to the 1970’s [3,4,6], White Sands Missile Range [7], and the Rocketball, Model-On-a-Wire (MOW) Facility [5] located at Redstone Arsenal, AL. All these facilities implement a single cable pulled to a desired tension and use rocket motors and/or gravity to accelerate the payload to velocity for data collection including target radar cross-section, sensor development, and aircraft target representation. All three facilities document peak velocities less than 300 m/s that are in the subsonic
A 1976 paper by Rodeman, Longcope, and Shampine [6] describes a test conducted at the Sandia
Facility in which a “sudden and dramatic failure occurred as the carriage was accelerated beyond the wave speed of the cable” at a velocity of 1.04c. Their analysis shows a singular cable response forms as a traveling mass is accelerated through the cable wave speed. At such time, two oppositely traveling jumps in displacement are formed and were validated in the test documentation through high-speed cameras. At a safe working tension of 4000 lbs on the 7/32” diameter steel strand to be used, the wave speed is 1082 ft/s—below Mach 1 and well below even the short-range engagement velocities of KE missile systems. In order to reach velocities in the Mach 1-3 velocity range on the steel cable, surpassing the cable wave speed would be unavoidable.


Any additional information on these programs (and especially pictures) would be most welcome. Also, I'm searching for an advertisement that was published in the early 90s as follows:

"There's a series of full-page ads running these days in engineering and computer magazines featuring aviation's own Burt Rutan. It's for a CAD program called Ashlar Vellum, and the ad is too funny for words-if you know what to look for. First there's a picture of Burt holding in mock-seriousness a propeller-head leather flying helmet, but apparently Ashlar didn't get the joke and thought it was a great shot of "one of America's most thought-provoking engineers" -- which indeed he is. Ashlar has just finished its second round of venture capital financing, having burned up the first round in over-promoting a very gimmicky program that techno-weenies love and draftsmen hate. In a way, it's a bit odd using Rutan to promote a CAD system, because as everyone knows, Rutan is a very bright guy and a skilled aerodynamicist, but his drafting skills have been the subject of insider-jokes among engineers for years. And Rutan openly admits he uses the program only for layouts and working out geometry and doesn't use the program for finished drawings. At the bottom of the ad, there's an example "engineering drawing courtesy Burt Rutan" -- an astonishingly crude drawing of a quarter-scale model airplane. It's called the 'SU-25 Roar', probably a model of a Sukhoi jet, with all straight lines and a tail on the back, scarcely resembling anything Rutan has designed."


If any of you owns this ad, I would be extremely grateful to see a scan of it!!!
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...ISTR this "Rocket on a Rope" technique is being used for lightning research, where a rocket is attached to a thin wire and fired from the top of a mountain into a thunderboomer, with the idea being to force a lightning discharge.
Not quite the same. The trailing wires are simply taking the role of a tall lightning rod whereas in the first case it's actually guiding the rocket. (Ironically when I was a kid and saw the term "wire-guided" I thought they were referring to this and always wondered how they got the other end of the wire hooked on the enemy tank LOL.)
sferrin said:
Not quite the same. The trailing wires are simply taking the role of a tall lightning rod whereas in the first case it's actually guiding the rocket. (Ironically when I was a kid and saw the term "wire-guided" I thought they were referring to this and always wondered how they got the other end of the wire hooked on the enemy tank LOL.)

...If it's any consolation, when I first heard the term "Fly-By-Wire" when I was about 3 years old, I thought it referred to those pre-RC Cox 049 engine planes that you flew around in a circle that were controlled like a puppet on a string. :p
Finally got hold of the Ashlar Vellum ad with Burt Rutan in it.

The SU-25 ROAR cad plan that appears at the bottom of the ad is reproduced here, and obviously it DOES have more than passing resemblance to the Sukhoi Su-25...



  • Su-25 ROAR cutout from ad (small).png
    Su-25 ROAR cutout from ad (small).png
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