- HADR — Humanitarian Assistance and Disaster Relief
- Military operations providing emergency humanitarian support including logistics, medical, engineering, and transport when civilian capacity is overwhelmed. Military acts as last resort under OCHA coordination. Governed by JP 3-29 and Oslo Guidelines.
Show the visualisation
- DiagramTry it: Ootw Guide SimulatorTry it: Ttps Guide
- HAE — Height Above Ellipsoid
- An altitude measured perpendicular to the reference ellipsoid, as reported natively by GPS.
Show the visualisation
- Hall Effect Thruster
- An electric propulsion device using magnetic field to trap electrons in a Hall current, ionising propellant and accelerating it electrostatically. Isp 1,200-2,000 s with higher thrust density than gridded ion thrusters.
Show the visualisation
- 3D modelTry it: Smad Orbit Visualizer
- Halo Orbit
- A periodic three-dimensional orbit around a Lagrange point (typically L1 or L2). Used for space telescopes (JWST at Sun-Earth L2) and solar observatories (SOHO at Sun-Earth L1).
Show the visualisation
- 3D modelTry it: Human Spaceflight GuideTry it: Interplanetary LaunchTry it: Ssa Guide+1 more
- HARM — High-speed Anti-Radiation Missile
- An air-launched missile that homes on radar emissions to destroy enemy air defense radar systems. Primary weapon for SEAD operations. Examples include AGM-88 HARM and AARGM.
Show the visualisation
- 3D modelTry it: Mil Ops Degraded EnvironmentsTry it: Defense Spectrum MapTry it: Defense Fundamentals Guide+1 more
- HARPOON — Harpoon Anti-Ship Missile
- An all-weather, over-the-horizon anti-ship cruise missile launched from ships, submarines and aircraft.
Show the visualisation
- HARQ — Hybrid Automatic Repeat reQuest
- A scheme combining forward error correction with retransmission of failed packets.
Show the visualisation
- HAVE QUICK
- US/NATO military UHF anti-jam communications system operating 225-400 MHz with frequency hopping. HAVE QUICK II provides enhanced ECCM for tactical air communications.
Show the visualisation
- 2D animationTry it: Multi Domain Spectrum PlannerTry it: Defense Spectrum MapTry it: Waveform Generator+1 more
- HAVEQUICK — Have Quick frequency-hopping system
- A US military UHF anti-jam frequency-hopping technique for protected air-to-ground voice.
Show the visualisation
- HawkEye 360
- Commercial RF-geolocation constellation. Clusters of 3 LEO smallsats locate VHF/UHF emitters via TDOA/FDOA. Maritime, vessel-spoofing detection, GPS-interference mapping use cases.
Show the visualisation
- 3D modelTry it: Constellation GuideTry it: Military Doctrine GuideTry it: Aerospace Defense Industry Guide+1 more
- HAZMAT — Hazardous Material
- Any substance that poses a risk to health, safety, or the environment during handling or transport.
Show the visualisation
- HCM — Hypersonic Cruise Missile
- Air-breathing weapon that sustains Mach 5+ flight throughout mid-course and terminal phases using scramjet propulsion. Flies at 20–40 km altitude — too low for space-based sensors and too fast for conventional air defense.
Show the visualisation
- 2D animationTry it: Defense Fundamentals Guide
- Heat Pipe
- A passive two-phase thermal transport device using capillary action to circulate working fluid between hot and cold zones with no moving parts.
Show the visualisation
- 2D animationTry it: Critical Thinking Sim
- Hellfire
- AGM-114 air-to-ground missile with multiple guidance variants (radar, laser, mmW). Primary armament for Apache helicopters and MQ-9 Reaper UAVs. Range ~8 km.
Show the visualisation
- 3D modelTry it: Defense Fundamentals GuideTry it: Defense Breakthrough GuideTry it: Joint Ops Guide+1 more
- Helmet-Mounted Sight — HMS/HMD
- A cueing display that shows target symbology and sensor data on a helmet visor, allowing pilots to slave sensors or missiles to head-pointing direction. Essential for high-off-boresight short-range air-to-air engagements.
Show the visualisation
- Diagram
- HEO — Highly Elliptical Orbit
- Orbits with high eccentricity providing extended dwell time over specific regions. Used for communications and early warning at high latitudes (e.g., Molniya, Tundra orbits).
Show the visualisation
- 3D modelTry it: Space Fundamentals GuideTry it: Human Spaceflight GuideTry it: Constellation Guide+1 more
- Hersey-Blanchard — Situational Leadership Model
- A leadership-style framework (1969) matching the leader's style — directing, coaching, supporting, delegating — to the follower's task-specific maturity (competence + commitment). Foundation of "no single best leadership style" thinking.
Show the visualisation
- DiagramTry it: Leadership Influence Guide
- HET — Hall Effect Thruster
- An electric thruster that ionizes propellant and accelerates ions through a magnetic and electric field.
Show the visualisation
- HF — High Frequency
- Radio band 3-30 MHz used for beyond-line-of-sight comms via ionospheric reflection (skywave). Long-range without satellite infrastructure but subject to propagation variability.
Show the visualisation
- 3D modelTry it: Defense Spectrum MapTry it: Mil Ops Degraded EnvironmentsTry it: Multi Domain Spectrum Planner+1 more
- HGA — High Gain Antenna
- A narrow-beam, high-directivity antenna requiring accurate pointing for high-rate communication links.
Show the visualisation
- HGV — Hypersonic Glide Vehicle
- A manoeuvrable re-entry vehicle that glides at Mach 5+ on non-ballistic trajectories. Challenges existing BMD by defeating trajectory prediction assumptions.
Show the visualisation
- 3D modelTry it: Mil Ops Degraded EnvironmentsTry it: Defense Fundamentals GuideTry it: Modern Warfare Guide+1 more
- HHC — Headquarters and Headquarters Company
- A company that provides command, staff, and administrative support to a battalion or brigade headquarters.
Show the visualisation
- HIDACZ — High-Density Airspace Control Zone
- Airspace with concentrated activity where special procedures are established to control operations.
Show the visualisation
- HIMARS — High Mobility Artillery Rocket System
- Wheeled precision strike system firing GMLRS rockets (70 km) or ATACMS missiles (300 km). Transportable by C-130. Prominent in the Ukraine conflict.
Show the visualisation
- 3D modelTry it: Modern Warfare GuideTry it: Defense Fundamentals GuideTry it: Waveform Generator+1 more
- HITL — Hardware-in-the-Loop
- Synonym for HWIL. Real hardware (avionics box, seeker, payload) closed-loop with simulated environment. Standard in aerospace V&V to qualify hardware behaviour before flight.
Show the visualisation
- DiagramTry it: Software Testing GuideTry it: Ttps GuideTry it: Digital Procurement+1 more
- HMAC — Hash-based Message Authentication Code
- A mechanism for message authentication using a cryptographic hash function combined with a secret key. Proves both data integrity and authentication — the receiver can verify the message was not altered and came from someone possessing the key.
Show the visualisation
- 2D animationTry it: Encryption Guide
- HMD — Helmet-Mounted Display
- A display integrated into a pilot’s helmet that presents flight and targeting information aligned with head movement.
Show the visualisation
- Hohmann Transfer
- The minimum-energy two-burn orbital transfer between two circular coplanar orbits, using an elliptical transfer orbit tangent to both. Requires two delta-v burns at perigee and apogee.
Show the visualisation
- 2D animationTry it: Smad Orbit VisualizerTry it: Space Fundamentals GuideTry it: Interplanetary Launch+1 more
- Honeycomb Panel
- A sandwich structure with thin face sheets bonded to aluminium or Nomex honeycomb core. High bending stiffness at low mass; standard panel construction in spacecraft.
Show the visualisation
- 3D model
- HPA — High-Power Amplifier
- Transmitter amplifier driving the antenna feed.
Show the visualisation
- HPM — High-Power Microwave
- A directed energy weapon that generates an intense burst of microwave radiation to disrupt or destroy electronic systems. Can disable electronics at range without kinetic destruction.
Show the visualisation
- 2D animationTry it: Ew GuideTry it: Space Fundamentals GuideTry it: Modern Warfare Guide+1 more
- HPMF — Hasty Protective Minefield
- Quickly emplaced minefield protecting a defensive position. Recorded on DA Form 1355-1-R, no anti-handling devices, emplaced beyond grenade range from friendly positions, and recoverable.
Show the visualisation
- Diagram
- HPRF — High Pulse Repetition Frequency
- A pulse-Doppler PRF regime that is unambiguous in velocity but highly ambiguous in range, used for high-closing-rate targets.
Show the visualisation
- HPT — High-Payoff Target
- A target whose loss to the enemy will significantly contribute to the success of the friendly course of action.
Show the visualisation
- HSC — Helicopter Sea Combat Squadron
- A naval helicopter squadron performing logistics, SAR and combat-support missions.
Show the visualisation
- HSI — Hardware/Software Interface
- The contract between hardware and software — register maps, interrupt behaviour, timing assumptions, discrete signal polarity, fault responses. Most integration defects on safety-critical programmes trace back to ambiguity or drift in the HSI.
Show the visualisation
- Diagram
- HSM — Hardware Security Module
- Tamper-resistant cryptographic appliance that generates, stores, and uses keys without ever exposing them to general-purpose software. Certified to FIPS 140-2/3 levels 2–4 and used for root-of-trust, code signing, payment processing, and KMS backends.
Show the visualisation
- DiagramTry it: Software Testing GuideTry it: Cyber Warfare Guide
- HSPA — High-Speed Packet Access
- A set of 3G enhancements improving uplink and downlink data throughput over UMTS.
Show the visualisation
- HTS — High Throughput Satellite
- A satellite using multiple spot beams and frequency reuse to deliver much greater capacity than conventional designs.
Show the visualisation
- HUD — Head-Up Display
- A transparent display that projects flight information into the pilot’s forward field of view.
Show the visualisation
- Human-in-the-Loop
- Autonomy mode requiring explicit human authorization for each lethal action. Standard for targeting engagements involving civilian risk; constrains throughput but preserves accountability.
Show the visualisation
- DiagramTry it: Ethics Standards GuideTry it: Ssa GuideTry it: Wargaming Methodology Guide
- Human-on-the-Loop
- Autonomy supervision mode where the system executes action cycles independently while a human monitors and can intervene. Common for drone swarms and automated air defenses (Aegis auto-mode).
Show the visualisation
- DiagramTry it: Modern Warfare GuideTry it: Ethics Standards Guide
- HUMINT — Human Intelligence
- Intelligence collected through personal contact — agents, informants, prisoners of war, refugees, diplomats, and open source exploitation. Provides unique insight into adversary intent.
Show the visualisation
- 2D animationTry it: Multiint Fusion GuideTry it: Mil Ops Degraded EnvironmentsTry it: Defense Missions Guide+1 more
- HVT — High-Value Target
- A target whose loss significantly degrades adversary capabilities or will. HVTs drive joint targeting priorities and often require multi-domain approaches to find, fix, and engage.
Show the visualisation
- 2D animationTry it: Ttps GuideTry it: Ootw Guide SimulatorTry it: Modern Warfare Guide+1 more
- HVU — High-Value Unit
- A ship whose loss would seriously affect the mission, warranting dedicated protection.
Show the visualisation
- HWIL — Hardware-in-the-Loop
- Closed-loop test where real hardware interacts with simulated environment in real time. Missile seeker + flight simulation, avionics + dynamic model, or radar + target generator. Cheaper than flight test and repeatable.
Show the visualisation
- DiagramTry it: Ttps GuideTry it: Software Testing GuideTry it: Digital Procurement+1 more
- Hydrazine
- A toxic liquid monopropellant (N2H4) used in spacecraft propulsion for attitude control and orbit manoeuvres. Decomposes over a catalyst bed. Being phased out for green propellants.
Show the visualisation
- 3D modelTry it: Smad Orbit VisualizerTry it: Space Fundamentals Guide
- Hyperspectral
- An imaging technique that captures data across many narrow, contiguous spectral bands (typically 100+), enabling detailed material identification through spectral signature analysis.
Show the visualisation
- DiagramTry it: Space Remote Sensing GuideTry it: Space Fundamentals GuideTry it: Multiint Fusion Guide+1 more
Questions this page didn't answer
Send them and we will answer directly, including the ones with awkward answers.
Get in touch