What is Shield: Definition and 65 Discussions

A shield is a piece of personal armour held in the hand, which may or may not be strapped to the wrist or forearm. Shields are used to intercept specific attacks, whether from close-ranged weaponry or projectiles such as arrows, by means of active blocks, as well as to provide passive protection by closing one or more lines of engagement during combat.

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  1. T

    Shielding against the Sun with a large sheet of aluminum foil in Earth orbit?

    Could people make a large sheet of aluminum foil and send it to the Earth's orbit to cover let's say half of the Sun and thus ease down these hot climate-change-induced summers? How feasible would something like this be? I know there was some talk years ago that a ring could be made around the...
  2. M

    I What is the best way to shield / jam ultrasound?

    I've downloaded SoniControl and it works somewhat well as a jammer, but I am looking for more options. I'm trying to shield from / jam Ultrasonic Cross-Device Tracking (uxDT). (See "data over audio" and "data over sound") Does anyone have any insight? I am a programmer, and not an...
  3. berkeman

    NASA Inflatable heat shield a ‘huge success’, NASA says

    Interesting optimization concept, to increase the size of the heat shield significantly to reduce the heat stresses during reentry... https://www.cnn.com/2022/11/17/world/loftid-heat-shield-nasa-success-scn/index.html
  4. Lotto

    B What magnetic fields can this hollow rod shield?

    I suppose it can shield only the external magnetic field, not the field of the magnet itself. But I am not completely sure.
  5. O

    Self-adjusting orbiting solar shield

    It is widely accepted that global warming caused by accumulating greenhouse gases is happening and, as the late Isaac Asimov pointed out years ago, even if or when this is curbed, if the population remains at similar levels as now then just the waste heat from human activities will eventually be...
  6. S

    I Could a bubble shield at L1 combat global warming?

  7. M

    I Making a heat shield for my car's exhaust

    Hello, I'm just wanting to make sure I remember this correctly. I have a hot exhaust pipe I want to shield from fuel lines. So I have a shield (stainless) that is going 1/2 way around the exhaust, with an air gap of about 1". I want to sand blast the side facing the heat and polish the side...
  8. A

    Electric Field Shielding: Does a Conductor Shield Inside?

    Hi. I was reading about conductors in electrostatic equilibrium and how it makes sense that they have zero electric field inside the material even when an external charge is brought near. The charge density of the material just rearranges itself to cancel. Then I searched for hollow conductors...
  9. S

    Face shield bleach disinfection

    Faceshield or respirators are getting to be as common as masks in public. What kind of bleach in basin can theoretically kill the Covid virus? What should be the concentration of bleach and now does it kill it?
  10. W

    Why a steel plate can shield magnetic field?

    If I put a very long steel plate above a coil with DC, the magnetic field above the plate will decrease because of the shielding of the steel plate. However, from the perspective of magnetci domain, some domains will be magnetized to turn to the direction of the magnetic field from the coil...
  11. G

    Exploring the Plausibility of SF Energy Shield Alternatives

    What could be the things closest to a SF energy shield? Even the strongest known materials couldn't stop shrapnels hit with 100 km/s. On the other hand, whipple shields are pretty efficient against high speed/low mass threats, the first armor plating disperse the micrometeor, then the second...
  12. J

    1 mm magnetic shield of pure iron same as 1 cm of mu-metal?

    When materials with high permeability are used to shield against low EMF frequencies of the order of 10 Hz, is the effectiveness linearly dependent on thickness and permeability? In other words, pure iron (mu=200,000) can be 10 times thinner than mu-metal (mu=20,000) for the same result with a...
  13. G

    Does an iron ring shield a static magnetic field?

    Hi. This picture shows an iron ring shielding a static magnetic field: Does this really work, and why? I know that a conductor can shield an electric field (Faraday cage) and a changing magnetic field (Lenz's law), but why would it shield a static field? Especially since iron is a ferromagnet.
  14. L

    Multi Pair Overall Shield Grounding

    On a multi-pair cable where each individual pair has its own isolated shield and there is one overall shield around all of the pairs, why do we ground the overall shield at both ends and the individual shields only at the cable origin. I can't find IEEE 518 right now, but i believe it tells you...
  15. S

    4WD Arduino Controlled car - Problem with motor shield

    I've been working with what will be a small Arduino 4WD controlled car, however now I've found a problem. The motor shield I used is an Arduino UNO motor shield R3, v3, which means that it can only control 2 motors, howerver I'll be using 4. Is there any way to use this same shild but apply all...
  16. E

    Creating an Energy Shield for Cars: Innovative Safety Technology

    Is it possible to create an energy for cars by having some kind of electron emitters built around the car or sound wave emitters to create a layer of dense airwave around the car to cushion any impacts to the car in an accident?
  17. infi

    Does an electromagnetic shield reflect?

    Let say a nanoparticle (graphene) is electromagnetic shield. If we send a pulse of magnetic wave will it get reflected back. If it reflects can that be interpreted. And what happens if there going to be infinite EM shielded nanoparticles. Is that any kind signal which will reflects back from...
  18. infinitebubble

    I Guarding Mars' atmosphere with a magnetic shield

    NASA scientists have proposed a magnetic shield that would sit at the L1 Lagrange Point beyond the planet, creating an artificial magnetosphere that would deflect solar winds and incoming radiation... Let's discuss thoughts and implications, engineering problems, etc. in such a formidable task...
  19. Planobilly

    How do I shield an amp setting on my work bench from EMI

    Hi, With all the various RF coming from things in my own house (cell phones, TV, cable modem, electric motors, etc.) and from outside I need to try to limit that interference while working on amps. Disregard for the moment, interference coming in through the AC mains. I also want to explore...
  20. N

    Shield against induction of sounds from remote source of RF

    It has been demonstrated that it is possible to make humans hear sounds using waves. Abstract From Journal of Applied Physiology Is there a practical method for shielding? I mean using materials for simple attenuation, and/or altering characteristics of waves (frequency, phase and/or amplitude).
  21. Sebastiaan

    Using Gamma Ray reflector to reduce mass of Shadow shield

    Let's say we have manned space vessel powered by a highly power but radioactive rocket engine, producing a lot of deadly gamma rays. The classical answer to this problem is to use a shadow shield. However, Nuclear Shadow Shields are very heavy. What about the idea of instead of trying to absort...
  22. N

    Why a conductive shield doesn't block the magnetic field?

    Hi While studying the shielded wires, i noticed that the magnetic field of the inner conductor can penetrate the shield conductor (can be calculated in the region 3). However, the boundary condition of the magnetic field at the surface (between dielectric and perfect conductor) of a perfect...
  23. R

    Heat transfer through AL shield by radiation & convection

    Hi all, I am new here, and want to thank you for help in advance! I am working on a project and need some help - I need to figure out surface temp on an object at some distance from the heat source: I need some help getting started. Is it going to be: Heat transfer (radiation) + Heat...
  24. rkum99

    Increasing current drawn in Arduino Motor Shield

    I am currently using the Adafruit Motor Shield in conjunction with an Arduino Motor Shield to control two 7.2V DC Motors. The DC Motors are being powered by a 7.2V, 3000 mAh Nimh battery. When the two DC Motors are being powered in parallel directly by the Nimh battery, they are able to move...
  25. DHF

    Writing: Input Wanted Designing a space ship and with the dust shield

    Hello everyone, I am designing a ship for my sci fi story and I need input regarding the shield. I am trying to make my story as hard sci fi as I can get away with. The story takes place a few centuries from now and details the first expedition to Alpha Centuri. The ship will have a cruising...
  26. Hexogen

    Wood Shield For Magnetic Field?

    So, I was watching PBS's Nazi Mega Weapons, and they were discussing the V-1 terror drone when they said something that made me scratch my head. They said that the Nazis initially had problems with the compass that facilitated navigation because of magnetic interference from the metal in the V-1...
  27. N

    HUD display on car's rear wind shield

    Hello Guys , I want to have my HUD displayed on my car's rear wind shield so that the driver just behind my car has an idea of my driving (Hypermilling) :cool: I have been looking for a possibility to do this but till now I only saw devices that projects the display on the front wind shield...
  28. ZapperZ

    Agents of SHIELD, Agent Carter, and the MCU

    So, I don't know if people are just not liking the series or if the Marvel Cinematic Universe (MCU) is not of any great interest. But I find it strange that there isn't an acknowledgment of a rather unique and unprecedented event that we have never seen before in the movie and TV industry...
  29. Krack

    Shielding & ground loop for audio

    I have a 3 conductor wire that are all wrapped in a foil shield with wire conductor, for a total of 4 wires. I am connecting the 3 inside wires to audio left, right, and ground. This is an unbalanced setup, right? Where/how do I connect the shielding? Do I connect both sides (i think no)...
  30. Symmetry777

    What is a Magnetic Screen or Magnetic Shield?

    What is a Magnetic Screen or Magnetic Shield? Soft Iron Magnetic Shield?
  31. thenewmans

    Heat on heat shield. Friction or compression?

    I always thought of a reentry vehicle compressing the air in front of it. And that would cause a lot of heat kind of like filling my tires. But I keep hearing friction even from NASA heat shield experts. OK, I guess maybe 10% of the heat is friction. I always assumed they said that to make the...
  32. C

    Heat Shield temperature question

    Hi all, new to this forum. I'm a member of University of Illinois at Chicago's Formula SAE team. I'm making the heat shield for our formula car and I was wondering if you guys and gals could help me with a heat transfer problem. We want to figure out what the temperature will be on the other...
  33. K

    Shield low-frequency magnetic fields, but not high-frequency ones

    I am wondering if it is possible to shield strong (1 Tesla) DC magnetic fields with high attenuation factor (10^4 or better) WITHOUT also shielding AC magnetic fields above frequencies of ~10kHz. I have looked at mu-metal, which as far as I can tell shields DC but also AC fields to some...
  34. T

    Plasma Physics Question - making a protecting shield

    I need to find the correct voltage to apply to a wire grid in order to repel a plasma of which I know the density (free electrons per volume) and the particle energy in eV. I see a Debye sheath as being analogous to what I will create with such a charge. The way I see it is that I will have...
  35. D

    Shielding - Need to ground an electrostatic shield?

    Shielding -- Need to ground an electrostatic shield? I am reading this app note by analog devices: http://www.analog.com/static/imported-files/application_notes/41727248AN_347.pdf At the bottom of the first page it says: "An electrostatic shield, to be effective..." "But grounding the...
  36. A

    Plasma frequency, shield, laser

    Homework Statement A plasma is to be used as a shield against a laser in the visible spectrum (400 - 700 nm wavelength light) by attenuating the field amplitudes. (a) What is the minimum electron density that should be used? (b) What thickness of this shield would be needed to reduce the...
  37. C

    How do you shield electronics from EMF?

    Hello all, I have an issue which I believe all you smart electrical engineers can help me with: How do you shield electronics from emf? I have a tablet pc with an active digitizer. The digitizer becomes inaccurate towards the peripheries of the screen --the closer to the bezel you are--...
  38. S

    Shield Magnetic Field: Best Material & Thickness for 10A Current

    Hi, If I run a current carrying wire through a tube of iron will it shield the magnetic field from outside the tube? That being true... what is the best material to use for the tubing (and why?)? and also, how thick would it need to be? Since thickness will probably be related to the...
  39. H

    Shield speaker magnet from activating reed

    My question pertains to model trains. I use a magnet under my last car to activate computer commands via a reed switch. One locomotive has a speaker placed near the bottom and the magnet of the speaker activates the reed switch - which I don't want it to do. One thought to correct this is to...
  40. cepheid

    Explaining the Science of Heat Shield Tiles on the Space Shuttle

    I came across an example figure in my first-year physics textbook depicting a tile of the same material used for the heat shield on the space shuttle. The tile is hot enough to be glowing red, and yet a person is holding it by the edges. The caption explains that this is due to the "extremely...
  41. M

    Creating a Drag Shield for a free fall object

    Would anyone know how to determine the area that a drag shield would have to be to allow an object above not to experience no more then .001 Gs? The drag shield that I was thinking about is just a flat sheet attached to the bottom of the top object by a string. Would this even be possible?
  42. C

    Captain America's shield bouncing

    So I finished watching the movie and they talk about how Captain America' shield is made out of vibranium, a material that is very good at absorbing energy. The shield bounces off walls like rubber. Does the ability to absorb energy actually make things more effective at bouncing?
  43. R

    Can someone explain the concept of a floating electrostatic shield?

    Hello, I am trying to fully wrap my head around signal shielding so as to take it from the trial-and-error domain to the theoretical design domain. The problem is that I am stuck on one of the very basic and fundamental principles of shielding - the floating conductor as an electrostatic...
  44. K

    Is a Plasma Shield Possible for Military Vehicles?

    Is it possible to make a plasma shield by using Radio Frequency from a microwave and making plasma. I know that part is possible, here's the tricky part. Having magnets with the right ratio of pull and push so the plasma can "shield" an object. So, is it possible?
  45. Crowxe

    Trapping Iron Plate Motion Using Magnetic Shield

    An iron plate would glide through magnetic field lines from the more separated towards the more condensed of a permanent magnet. If we use a magnetic shield to make a trap where that iron plate finds itself in dead area (no magnetic field lines) then it would continue the motion it gained...
  46. H

    Captain America's shield properties

    In comics, Captain America's shield can absorb an incredible amount of kinetic energy from impacts (if not all of it) because of its vibranium makeup. That is why he can block hits from super-strong beings like Hulk without any damage done to him or him going backwards. But when he throws the...
  47. F

    I need to shield Earth's Gravitational force.

    What is out there in the universe that shields strong gravitational forces?
  48. B

    Help- can I shield a magnet so it won't damage my phone?

    I feel a little silly for posting this rather mundane question- but I really am at then end of my (limited) wits. I have an iPhone, and there is a rather strong magnet on my favorite purse (I believe it is a neodymium magnet, but don't know for sure). I have been researching this issue online...
  49. N

    Why can we shield some forces but not others?

    I'm wondering why we can shield ourselves from electromagnetic and nuclear radiations but not gravity. Are there any mathematical suggestions/insights/explanations? (I'd hope for a written explanation/interpretation rather than a long string of formulas!) I'm pretty sure no one knows the...
  50. S

    Could Plasma Be the Future of Re-Entry Heat Shield Technology?

    Is it possible to use plasma as a heat shield for a re-entry vehicle? We all know that plasma isn't very dense, but then neither is the thin upper atmosphere that causes re-entry heating in lieu of drag. I'd read that a simple trick used by ICBM warhead engineers, was to simply have a...