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"Americans Flying Rockets Are Not Terrorists!"

Copyright © 2003 Amateur Rocketry Society of America

Answers To The Department of Justice &
ATFE Anti-Rocketry Propaganda Campaign!

The Amateur Rocketry Society of America

Background Information

After the terrorist incident of September 11th, the United States Congress with the full support of the White House passed the Patriot Act and the Homeland Security Act. The Homeland Security Act has had a devastating affect on rocketry in the United States. It requires that American citizens obtain permits from the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATFE) in order to fly rockets consisting of cardboard tubes, plastic nosecones and fins. In order to obtain this permit, the applicant has to be finger printed, supply information for a background check and pay a $100 fee plus the costs of be finger printed by local law enforcement. In order to receive the permit the applicant has to show access to a federally approved explosive storage facility. Ironically, the propellant and rocket motors used are not explosives. As one would suspect, most people cannot obtain access to an explosive storage facility. Most residential neighborhoods are not keen on neighbors putting explosive magazines in their back yard and apartment managers are most definitely against them in apartments. Very few companies with federally approved explosive storage facilities are going to let "Joe Citizen" walk in off the street and use the company's explosive magazine.

The result of the Homeland Security Act has been thousands of Americans dropping out of hobby rocketry. This has been reflected by sales declines on the order of 70% to 80% for businesses selling hobby rocket motors, rocket kits, electronics and various other supplies. The law has also had a chilling effect on private university aerospace engineering courses that offer "hands-on" rocketry to students. These universities include MIT, Caltech, Syracuse, Stanford, Princeton, John Hopkins, Florida Institute of Technology and Embry-Riddle Aeronautical University.

In response to this over regulation of American universities and a harmless hobby, ARSA drafted a bill to provide an exemption for rocketry in the Homeland Security Act. The bill was refined and introduced by Senator Mike Enzi (R) from Wyoming on March 27, 2003.

Click here for the text of Senator Enzi's speech introducing his bill - S724.

Since the introduction of S724, the Department of Justice and ATFE have been feeding misinformation to the media and Congress in an attempt to defeat or severely weaken the bill. The Department of Justice's concerns and opposition to S724 were first publicly expressed in a letter written to Senator Hatch, chairman of the Senate Judiciary Committee. These concerns were amplified and expressed again by Senators Schumer and Lautenberg during a press conference on July 29, 2003.

Department of Justice Letter to Senator Hatch.

Click here of Senator Schumer's press release on S724

In response to the misinformation promoted by the ATFE and Department of Justice, ARSA has conducted research on each of the false claims. Below we present the facts on one these false claims.

Rocketry A Threat To Civilian Aviation?

The Department of Justice (DOJ) claims that amateur and hobby rockets can be used to shoot down civilian and military aircraft. They claim this can be done as these aircraft cruise at normal operating altitudes and speeds.

DOJ Letter: "Moreover, it bears noting that hobby rocket motors containing large amounts of APCP can power extremely large rockets more than 20,000 feet into the air, frequently requiring high-power rocketry hobbyists to obtain waivers from the Federal Aviation Administration prior to a launch. These large rocket motors could potentially be adapted by terrorists for use in surface-to-air missiles capable of intercepting commercial and military airplanes at cruise altitude"

Let's examine the case where a civilian or military aircraft is at cruise altitude and speed. For most military and civilian aircraft this would on the order of 30,000 ft to 40,000 ft and a speed of approximately 500 mph. The DOJ letter specifically mentions 20,000 ft, so we will present results for that altitude as well. The terrorist will have to aim his rocket so that it hits a precise spot in the sky just as the aircraft reaches that point. In order to calculate a launch angle error limit, it was necessary to assume an aircraft length. We assumed a length of 155 ft, the length of a Boeing 757 airliner. The tolerance for the launch angles shown in the tables below is for elevation. The tolerance in the azimuth launch angle is even tighter due to the width of the plane being so much smaller than its length.

In the analysis, we assumed that the terrorist would wait until the plane passed directly overhead and then fired his rocket. As it turns out by simple velocity vector analysis, the launch angle will always be the same if the velocities of the aircraft and missile are the same. It is assumed in the analysis that the speed of the aircraft and rocket does not vary in-flight and that the rocket instantly achieves its speed once it is launched, which was 1,500 mph. While the launch angle does not change, the accuracy of the launch angle must increase as the altitude of the aircraft increases. Also, as the altitude increases, the time for the rocket to impact the aircraft increases as does the movement of the plane from rocket launch to rocket impact.

Amateur Rockets Against Aircraft While Cruising
Rocket Speed Is 1,500 mph
Table 1
Aircraft Altitude (Ft) Launch Angle (Deg) Error Angle (Deg) Time To Impact (Sec) Plane Movement (Ft)
20,000 19.47 0.2 9.64 7,071
30,000 19.47 0.13 14.46 10,607
40,000 19.47 0.10 19.28 14,142

A couple of conclusions can be made based on this simple analysis. First, in order for the rocket to hit the airplane, it must travel in a straight line. At a launch angle of 19.47 degrees from vertical, that is not going to happen. Instead, it is going to go into a gravity turn which will cause the rocket to miss. There is also the problem of wind which will not only alter the path of the rocket, but the ground track of the aircraft as well. Again, this will cause the rocket to miss the aircraft.

Second, the tolerance for setting the launch angle ranges between 0.1 degrees to 0.2 degrees. This is a very precise angle and would be difficult to measure under the field conditions that the terrorist must operate under. The launch rod or rail must not flex even a fraction of a degree or the rocket will miss its target. The launch rod or rail must be very well anchored to the ground or it will move as the rocket travels up the rod or rail. To anchor it to this degree will require the terrorist to go to some elaborate lengths, if it possible at all with a mobile launcher. It is definitely not something that will be put up quickly or adjusted should the plane change course before launch.

Third, the missile's speed must be set well into the supersonic range for reasonable launch angles and impact times. Look at the time to impact or the time the rocket motor must be firing to maintain the required speed. The rocket motor burn times would range between 9.6 seconds and 19.3 seconds. These long burn times would be impossible to achieve with the small diameter amateur or high power rockets required to fly supersonic.

There is the problem of aerodynamic heating of the rocket at supersonic speeds. The materials used in typical amateur or high power rockets would begin to melt at supersonic speeds. If the terrorist launches the rocket at a more typical amateur or high power rocket speed of around 300 mph as the plane passes overhead, the rocket will never catch up with the plane. In order for this relatively slow moving rocket to hit the plane, the terrorist must launch the rocket before the plane passes overhead. He must fire the rocket as the plane approaches him. But what happens when the pilot of the aircraft sees a rocket taking off directly in front of him on the ground with a large white smokey exhaust? The pilot will change speed, course and altitude to avoid the rocket. This actually can be a leisurely maneuver as the it would take the rocket about 45 seconds to reach 20,000 ft and a little over 90 seconds to reach 40,000 ft. The rocket is going to miss the aircraft and the terrorist fails. He will also be easily apprehended by law enforcement as the pilot will be able to radio the terrorist's exact coordinates to authorities.

The bottom line is that a terrorist would have no chance of success in hitting an aircraft at cruise altitude and speed with an amateur or high power rocket. The statement of a threat by the Department of Justice is a lie that can be disproven by even the simplest analysis.

What about when an aircraft is on approach to an airport? Then, it is flying slower and lower, which would make it more vulnerable as shown in the "Threat Area" graphic below. Let's take a look at the situation assuming the aircraft is at an approach speed of 155 mph that is typical for a Boeing 757.

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First, let's use a rocket speed of 1,500 mph and have the terrorist launch the rocket as it the aircraft comes overhead. Intuition tells you that this would be an easier shot than trying to shoot down an aircraft at altitude. It is easier, but the tolerance on the launch angle is still tight, Table 2.

Amateur Rockets Against Aircraft On Approach
Rocket Speed is 1,500 mph
Table 2
Aircraft Altitude (Ft) Launch Angle (Deg) Error Angle (Deg) Time To Impact (Sec) Plane Movement (Ft)
2,000 5.93 2.18 0.91 207
5,000 5.93 0.89 2.28 519
10,000 5.93 0.44 4.57 1,039

Of course, a rocket velocity of 1,500 mph is a lot faster than a typical amateur or high power rocket. If the rocket speed is set at 300 mph, the tolerance for the launch angle is even tighter, Table 3. In either case the launch angle tolerance is around two degrees and that is when the plane is only 2,000 ft above the ground. To set up a mobile launcher so that the launch angle is within two degrees is not possible due to flex in the launch rail or rod and the movement of the entire launch platform during launch. Again, the terrorist is going to miss the target.

Amateur Rockets Against Aircraft On Approach
Rocket Speed Is 300 mph
Table 3
Aircraft Altitude (Ft) Launch Angle (Deg) Error Angle (Deg) Time To Impact (Sec) Plane Movement (Ft)
2,000 31.11 1.6 5.3 1,206
5,000 31.11 0.65 13.27 3,017
10,000 31.11 0.32 26.5 6,034

For an amateur or high power rocket to hit an aircraft during cruise or approach to an airport, it would have to be guided during its flight. The addition of a guidance system would change the rocket to a missile. How easy would it be for a terrorist to build a guidance and control system for an amateur or high power rocket? Unless the terrorist was a skilled engineer in solid rocket control and a skilled engineer in tactical missile guidance software and hardware, he will fail in creating such a system. But if the terrorist is going to use a guided missile, why make one?

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There are plenty of anti-aircraft missiles in the hands of terrorists now. They are called Man-portable Air Defense Systems or MANPADS. Bob DelBoca, Vice President of Infrared Countermeasure Systems for Northrop Grumman Corporation, gave testimony this year before the House Transportation and Infrastructure Committee Aviation Subcommittee. Mr. DelBoca said, "MANPADS are easy to use, require minimal training, and can be set up to fire in less than three minutes. They have also been highly proliferated. According to Jane's Intelligence Review there are an estimated 500,000 MANPADS worldwide. Fortunately, a good majority of them are under the control of responsible governments. Unfortunately, they are also available on the arms black market for between $25,000 and $80,000. At least 27 terrorist and non-state groups are believed to have MANPADS in their arsenals. Worse yet, these weapons are also deadly. Many have ranges of more than four miles and can reach aircraft flying at over 10,000 feet."

It is time for the Department of Justice and ATFE to start telling the truth to the media and Congress. The truth is that amateur and high power rockets would be absolutely useless in an attempt to shoot down military or civilian aircraft. Terrorists are not going to use something useless when they already have in their possession MANPADS that can shoot down military and civilian aircraft.

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