The delivery of biological weapons is different from conventional weapons in that a lot of extra care has to be taken to ensure that the microorganisms do not get inactivated while being transported to the intended site of attack.
Besides this, there is the problem of dispersion of the germs. Bioweapons , when utilized, should disperse the germs over a large area so that a large number of people are affected. Even if you are using an agent like smallpox which shows person to person transmission, it would be more destructive to have a large population infected initially, so that the "chain reaction" has a good head start.
It is for this reason that a brief explanation of how bioweapons are prepared
for delivery is required:
Preparing your germs for the final journey:
Stabilizing the microorganisms :
A much more advanced technique whereby the microorganisms can be protected is by encapsulating the infective particles with a protective covering. Such encapsulation, however, is not necessary for weaponization. I have no technical details regarding this particular technique.
Ensuring dispersion of the Microorganisms:
In general, the smaller the particles the better the dispersion. However,
particles smaller than 1micron are counter productive since they are exhaled out
by the human respiratory tract. In other words, particles less than 1micron do
not STICK or are not retained in the lungs. Since the aim is to deposit the
particles in the lungs and make the person sick, the "infective
particles" in biological weapons are slightly more than 1-2microns in
Explanation of the graph :
Note the size of the particles that are maximally retained by various parts of
the respiratory system.
The following is an extract from "The Bioweaponeers" :
The distribution of Death :
You just cannot fix the vials of your microorganisms on top of some RDX and blow the whole thing up so as to disperse the germs over a wide area. The efficacy of delivery of biological agents by explosive agents is estimated to be ~ 1-5%. Hence, more troublesome methods e.g. aerosol spraying (efficacy 40-60%) are employed.
The delivery vehicles may range from simple crop spraying planes
to complex intercontinental missiles with refrigerated warheads. The former
would be of use to the cash-starved bioterrorist while the latter is the
preserve of nation-states engaged in this sort of research.
1) Aerosol Spraying :
Click on the images to view larger ones.
Crop spraying planes are routinely used in the US for spraying pesticides over vast expanses of land. If you have seen one of these small planes in action (e.g. in the movie Independence Day), you have an idea about the large area a moderate sized sprayer would cover in a day.
Image : A handheld crop-sprayer. And no.. that Vietnamese guy isn't me.
News Flash : After the WTC bombings on Sept. 11, the US authoritites announced that stricter security checks would be carried out on all pilots operating crop spraying planes. The regulations for sale of such planes were also made much more stringent. ( Times of India , Sept 2001)
2) The more advanced systems :
These are usually in the form of missiles, or as parachuted bombs with little or no explosive to be dropped from planes.
The Russians employed missiles called MIRVs which had multiple warheads (up to 10) each targeted at a different location. The part of the missile where the germs were stored was refrigerated in order to protect them from the heat of reentry into the atmosphere. Parachutes are then used to slow down the descent of the warheads once they are released from the mother missile. The microorganisms to be used were presumably in a highly dispersible form (e.g. the Alibekov strain of Anthrax).
Multiple warheads. These 3 warheads are of the Minuteman 3 , a US
InterContinental Ballistic missile (ICBM).
The rest of the description is from "The Bioweaponeers" :
The Iraqis had admitted to having an arsenal of 16 missile
warheads filled with botulinum, five with anthrax bacillus, and four with
aflatoxin. They claimed to have destroyed these before the start of the Gulf
war. However, a report by the US senate Research Service in April 1998 suspected
that Iraq may still have hidden from 2-10 warheads designed to deliver chemical
or biological agents.
I do not have information regarding the US delivery systems for