In Star Trek, even at 'low' impulse speeds, colliding with a Very Tiny Object would be horribly damaging to the ship - see this NASA.org link which describes space shuttle windows being damaged by impact from paint flecks at high-velocity. To combat this, starships come equipped with deflector dishes; these are alleged to sweep the flight path of dust and debris and sometimes even provide some techno-magic Big Push to save the day against various objects of large mass - asteroids, the Borg, Paul Sorvino, and so on.

Finally, starships are also equipped with Bussard collectors. While these get very little on-screen explain time and even less emphasis on importance, these handy devices allow starships to scoop up particulates which the ship can use to 'refuel' - sort of a big giant Mr. Fusion.

But wait - the deflector dish is supposed to sweep particles aside, right? So in order for the collectors to even work, a ship would need to disengage the deflector dish, wouldn't it? Even at the low speeds we attain today, if a paint fleck moving at 18,000 mph can crack a window, what happens to a starship when it finds a particle moving at .25c?

Am I overlooking something (besides "it's only a show, just relax", or can these two technologies even exist in tandem?

  • 3
    besides "it's only a show, just relax" How do the bussard collectors work? They work just fine, thank you.
    – user16696
    Mar 11, 2015 at 2:23

4 Answers 4


The deflector array is essentially a set of small tractor beams controlled by an advanced targeting system with super fine sensors. Any particle of matter of sufficient size and hazardous nature is gentle and quickly pushed away from the ship. As it works with the standard starship sensor instruments, it can be calibrated to detect or ignore certain particles and not others. There would be no conflict between the deflector and the collector unless someone programs it that way.

In fact, the TNG Technical Manual explains exactly how this works, at both sublight and warp speeds:

The magnetic field generator/collector [part of the Bussard system] is a compact set of six coils designed to cast a magnetic "net" ahead of the starship and pull in the charged particles toward the intake grills. ... At sublight velocities, the coils sweep forward normally. At warp velocities, however, the coil operation is reversed to slow down the incoming matter. This system works in close connection with the main navigational deflector. In normal operation, of course, the job of the deflector is to prevent any interstellar material from contacting the ship. Small field "holes" are manipulated by the deflector and MFG/C to permit usable amounts of rarified gas through.

Not only does the Bussard system work with the Deflector system to allow certain particles through, it even slows the particles down to prevent high C explosive impact events. Furthermore, the system operates at subspace frequencies allowing it's magnetic fields to go through warp bubbles properly. They thought of everything.


Focusing on your sub-question "what happens to a starship when it finds a particle moving at .25c," know that at about 3km/s, an object's kinetic energy is equal to its mass in TNT. This means that adding an explosive warhead to anything faster than that is superfluous.

To quote from projectrho (a sci-fi time-sink of a website with an example calculation wherein Sneaky Cat dumps his litterbox into the path of a starship):

How much damage would the 7 kilograms of used kitty litter from Sneaky the cat's litterbox inflict if it was traveling at a velocity of 90% c?

Ker = ((1/sqrt(1 - P2)) - 1) * M * 9e16

Ker = ((1/sqrt(1 - 0.92)) - 1) * 7 * 9e16

Ker = 8.2e17 Joules, about 195 megatons.

Not bad, for kitty litter.

P2 = percentage of speed of light, so for your calculation use .25

  • "at about 3km/s, an object's kinetic energy is equal to its mass in TNT. This means that adding an explosive warhead to anything faster than that is superfluous" It's only superfluous if the explosive warhead has an equivalent explosive power per unit mass as TNT! If the warhead was something like antimatter, then adding a warhead wouldn't become superfluous until the kinetic energy became equal to the rest mass energy, and kinetic = (gamma - 1)mc^2 and rest mass = mc^2, setting them equal gives gamma(mc^2) = 2mc^2, which happens when v = 0.707c.
    – Hypnosifl
    Sep 26, 2015 at 23:19
  • Having high kinetic energy negates the benefit of a warhead if you're just talking about two objects in space. As user16696 referenced in their answer, shields deflect incoming objects and energy away from the ship. The push absorbs the kinetic energy, then has to absorb the energy of the explosion, making it no longer superfluous.
    – Merennulli
    Jan 13, 2016 at 19:52

Via http://en.memory-alpha.org/wiki/Bussard_collector

The Bussard collector, also known as a Bussard ramscoop or ramscoop, was a device usually attached to the forward end of a warp nacelle. The Tosk variation of the Bussard collector was known as the arva node. The collector, along with the Bussard collection coil, was called a Bussard unit. (TNG: "Silicon Avatar", okudagram; DS9: "Captive Pursuit")

All Federation starships were equipped with Bussard collectors, which were positioned in the best line of sight to collect interstellar particles. Collection worked best in regions where particle density was high, such as in star systems or nebulae. The Bussard collector normally collected hydrogen, especially deuterium, for fuel replenishment, but could be reconfigured to collect various gases like sirillium and plasma particles. A Bussard collector could also be reconfigured to expel gases or plasma. (TNG: "Samaritan Snare") Bussard collectors were not capable of producing nadion emissions. (VOY: "The Haunting of Deck Twelve")

Aboard the Galaxy-class USS Enterprise-D, in the Engineering Systems Database, there was a folder titled "Bussard Collection Field Operations". This folder contained technical manuals relevant to the topic. (TNG: "Booby Trap", okudagram)

I owned the TNG Enterprise engineering manual years ago and if memory serves, it stated that the goal was to collect atomic hydrogen or deuterium when available. The quantities available were never adequate to completely replenish a starships tanks inflight, but the option of passing into a nebula gas cloud or the like certainly would.

The pics below contain too much info to relay so I included them.

enter image description here

enter image description here

Here are the links to the above images http://4.bp.blogspot.com/-6QoqtEl2Hvc/TsqOJQTzOlI/AAAAAAAAEcA/gEDNCkuagWE/s1600/Build+the+Enterprise+Bussard+Collectors.jpg


Follow this link for the actual Technical manual. The link opens to the section where you can read exactly how the Bussard collectors work. They are in-fact effected by the warpfield at speed.


In specific detail to the OP's question:

This system works in close connection with the main navigational deflector. In normal operation, of course, the job of the deflector is to prevent any interstellar material from contacting the ship. Small field "holes" are manipulated by the deflector and MFG/ C to permit usable amounts of rarified gas through.

Source: Technical manual

  • You could also link to the blog post where those images (and others from the Build the USS Enterprise magazine) were posted: Build the Enterprise, Issue by Issue
    – Hypnosifl
    Mar 10, 2015 at 16:02
  • 1
    BTW, while your answer gives a lot of details on the Bussard collectors, it doesn't really address the main question of whether the deflector shields would push the hydrogen away. Looking at the second of those magazine images, there's a line that addresses this: "Operation of the Bussard ramscoops necessitates manipulation of the Enterprise's deflector shields to enable the passage of the hydrogen. The magnetic field of the collectors would not be able to attract them through the shield without such modification." If you add this line to your answer I think it would make it more complete.
    – Hypnosifl
    Mar 10, 2015 at 22:15

Those cannot be "Bussard Collectors". Wouldn't work. To begin with a Bussard collector would need to project an electromagnetic field in a cone at least 6,000 kilometers across ahead of the ship. The nacelles are placed so that those fields would project right thru the saucer section which would interfere with them. This would leave you with only a partial cone which wouldn't work. Even if you eliminate the saucer section the two cones would interfere with each other and you still won't collect anything. A Bussard collector would ONLY work if it has a single point of emanation positioned at the very forefront of the ship, there are no other fields to interfere with it and you remain at sub-light velocities...

  • Maybe so, IRL, but there's a bunch of supplementary stuff that identifies that part thusly. I think there may even be some dialog on the show that does as well. Feb 26, 2018 at 19:31
  • "Also warp drive and transporters aren't real!" Downvoted. Jun 19, 2018 at 1:42

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