Lightning causes more than $1B/year in direct damages to property in addition to the loss of lives, disruption of activities (for example, postponement of satellite launches) and their corresponding costs. A better understanding of the physics underlying lightning discharge, associated emissions, and related processes (for example, tribocharging in the clouds) may lead to revolutionary advances in the state of the art of lightning protection.
DARPA is soliciting innovative research and development (R&D) proposals through the NIMBUS program on the underlying science of lightning. Proposed research should investigate innovative approaches that enable revolutionary and fundamental advances in atmospheric and ionospheric science relating to lightning. Specifically excluded is research that primarily results in incremental or evolutionary improvements to the existing state of practice or knowledge.
Although significant progress has been made in recent years in our understanding of the lightning discharge and related phenomena, fundamental questions remain unanswered. This program will develop the broad, fundamental science necessary to formulate:
- An experimentally validated, quantitative model of the natural lightning process, including initiation, propagation, and attachment;
- An experimentally validated, quantitative model of the rocket-triggered lightning process, including initiation, propagation, and attachment;
- An experimentally validated quantitative model describing the triggering of transient luminous events (TLEs), lightning-induced electron precipitation, and related ionospheric phenomena;
- A quantitative model of any other process that is demonstrably fundamental to the understanding of physical phenomena associated with lightning;
- An optimal strategy to reduce the probability of lightning strikes in a given area in the presence of a thunderstorm.
Solving these challenges will lead to better protection of personnel, assets, and ordnance, as well as improve the performance of radio frequency communications, electronics, and power systems.
BACKGROUND
The mechanism of lightning initiation inside thunderstorms is one of the major unsolved mysteries in the atmospheric sciences. Until recently it has been the common view that in order for lightning to initiate at some location in a thundercloud, the electric field intensity at that location must reach a value large enough for conventional electrical breakdown to occur (about 2.6 x 106 V/m).
However, decades of electric field measurements inside thunderstorms have failed to find electric field strengths close to the conventional breakdown threshold, even when the effects of precipitation and the lower pressure at cloud charge altitudes are taken into account. Alternative hypotheses explaining lightning initiation are various forms of runaway breakdown. All of these can potentially occur at lower electric field strengths than conventional breakdown.
An equally important mystery is how lightning propagates. It is known that in order to travel great distances through air, lightning forms a hot conductive channel called a stepped leader. The leader provides a conductive path for the transport of electrical charge, allowing the lightning to propagate out of the thundercloud into regions with low ambient electric fields.
For most lightning, this is accomplished by the negative stepped leader, which propagates in a series of discrete steps, roughly 50 m in length. Exactly how and why lightning moves in this way remains a mystery. Because the lightning stepping process determines where lightning travels and ultimately what it strikes, understanding this process is crucial for lightning protection and safety.
The lightning initiation processes in the thundercloud have been relatively inaccessible to close measurement. However, lightning that is initiated near ground level and propagates upward into the thundercloud charge can be studied at close range using a triggering system.
The electrical discharge that is initiated closely resembles the latter portion of natural downward lightning. Nimbus will seek to use rocket-triggered lightning as a tool to investigate the initiation, propagation, and attachment of lightning, as well as the triggering of associated processes (e.g., transient luminous events, lightning-induced electron precipitation, etc.)
PROGRAM GOALS AND MILESTONES
DARPA’s interest in lightning and atmospheric electricity centers on protection of personnel, assets, and ordnance from possible injury, damage, or disruption from lightning activity. The major thrust of the Nimbus program is to obtain a solid understanding of lightning and associated physical phenomena in order devise strategies to protect personnel, assets and ordnance. Specifically, the goals of Nimbus are to produce:
- Experimentally validated, quantitative models of the natural lightning process, including initiation, propagation, and attachment. Questions include: what measurable quantities are important to understanding these processes? How can they be estimated from ground measurements?
- Experimentally validated, quantitative models of the rocket-triggered lightning process, including initiation, propagation, and attachment, based on quantities that can be measured from the ground. This model should include predictions, based on relevant parameters (e.g., storm type, location, size, electric field strength, rocket speed, etc.), of the probability that lightning can be triggered using a rocket.
- Experimentally validated, quantitative models of the triggering of transient luminous events (TLEs), lightning-induced electron precipitation, and related ionospheric phenomena, using rocket-triggered lightning.
- Experimentally validated, quantitative models of any other process that is demonstrably fundamental to the understanding of physical phenomena associated with lightning. Examples of such phenomena might include: terrestrial gamma ray flashes (TGF), production of x-rays, sferics, compact intra-cloud discharges, tribocharging in clouds, etc
- Optimal strategies to reduce the probability of lightning strikes in a given area in the presence of a thunderstorm. Given an area (size: 1 square kilometer) in the presence of a thunderstorm, is it possible to reduce the probability of a cloud to ground lightning strike in that area? How might lightning initiation be inhibited, or lightning propagation be diverted or blocked to achieve this goal? Is it possible to induce lightning in one region within the storm system, in order to suppress lightning in the region in need of protection? What are the optimal strategies, and the necessary resources, to achieve this goal?
DARPA invites proposals seeking to accomplish one or more of the above goals of the Nimbus program. Proposals seeking to achieve more than one goal should be structured into options where each option addresses only one goal. A successful proposal will identify the obstacles to reaching the proposed goals, describe in detail the experimental and theoretical efforts that will overcome these obstacles, and justify that proposed personnel and equipment are sufficient and appropriate to carry out the research effort. Teaming is highly encouraged.
Documents:
DARPA-BAA-10-18
Type: Other (Draft RFPs/RFIs, Responses to Questions, etc..)
Posted Date: December 16, 2009
Type: Other (Draft RFPs/RFIs, Responses to Questions, etc..)
Posted Date: December 16, 2009
Agency contact:
The BAA Administrator for this effort can be reached at:
DARPA/DSO
ATTN: DARPA-BAA-10-18
3701 North Fairfax Drive
Arlington, VA 22203-1714
Solicitations can be viewed at:
