Ivan Tuzikov Posted February 3, 2016 Share Posted February 3, 2016 https://en.wikipedia.org/wiki/Timeline_of_telescopes,_observatories,_and_observing_technology http://www.projectrho.com/public_html/rocket/spacewardetect.php The second link specifies calculations for the following: chemical rockets; fusion engines, ion drives, steady-state plasma drives - most types of torchships. Taking into account the aforementioned links could somebody please answer me at which point of astronomic observations (the year, or decade) was it possible for Terran astronomers to detect the incoming spacecraft (interstellar or interplanetary) by its exhaust plume? Link to comment Share on other sites More sharing options...
swansont Posted February 3, 2016 Share Posted February 3, 2016 https://en.wikipedia.org/wiki/Timeline_of_telescopes,_observatories,_and_observing_technology http://www.projectrho.com/public_html/rocket/spacewardetect.php The second link specifies calculations for the following: chemical rockets; fusion engines, ion drives, steady-state plasma drives - most types of torchships. Taking into account the aforementioned links could somebody please answer me at which point of astronomic observations (the year, or decade) was it possible for Terran astronomers to detect the incoming spacecraft (interstellar or interplanetary) by its exhaust plume? Do we do any detection by looking for an exhaust plume? Would there be an exhaust plume? Most craft spend the bulk of their time with the rockets turned off. Link to comment Share on other sites More sharing options...
Ivan Tuzikov Posted February 4, 2016 Author Share Posted February 4, 2016 Do we do any detection by looking for an exhaust plume? Would there be an exhaust plume? Most craft spend the bulk of their time with the rockets turned off. 1. How else can we detect (alien / in radiosilence mode) spacecrafts in deep space? 2. Of course, but to gain the required speed the spacecraft has to fire its engines for some period of time. Link to comment Share on other sites More sharing options...
swansont Posted February 4, 2016 Share Posted February 4, 2016 1. How else can we detect (alien / in radiosilence mode) spacecrafts in deep space? The same way we detect other objects? 2. Of course, but to gain the required speed the spacecraft has to fire its engines for some period of time. Which they would do at the beginning of their journey, far away from us. Link to comment Share on other sites More sharing options...
Ivan Tuzikov Posted February 4, 2016 Author Share Posted February 4, 2016 The same way we detect other objects? Which they would do at the beginning of their journey, far away from us. Telescopes? What about breaking, at the end of their journey? 1 Link to comment Share on other sites More sharing options...
swansont Posted February 4, 2016 Share Posted February 4, 2016 Telescopes? What about breaking, at the end of their journey? That would be the only time you could hope to discover the plume. If interstellar travel were actually feasible, that would be very late in the game. Link to comment Share on other sites More sharing options...
Ivan Tuzikov Posted February 4, 2016 Author Share Posted February 4, 2016 That would be the only time you could hope to discover the plume. If interstellar travel were actually feasible, that would be very late in the game. You are getting close to my initial questions, actually 2 main questions: The first one: possibility of detection of plume in case of interplanetary travel in the Solar system (Earth-bound). The second one: at which point of astronomic observations (the year, or decade) was it possible for Terran astronomers to detect the incoming spacecraft (interstellar or interplanetary) by its exhaust plume? P.S. Please, do not answer in riddles or parry my questions, I'm neither astronomer nor scientist (sadly). Any useful links would be of much help. Thanks in advance. Link to comment Share on other sites More sharing options...
swansont Posted February 4, 2016 Share Posted February 4, 2016 You are getting close to my initial questions, actually 2 main questions: The first one: possibility of detection of plume in case of interplanetary travel in the Solar system (Earth-bound). The second one: at which point of astronomic observations (the year, or decade) was it possible for Terran astronomers to detect the incoming spacecraft (interstellar or interplanetary) by its exhaust plume? Since this is not how we do the detection of our craft, and such a scenario has never existed, this is tough to answer as posed. If the reaction is from something that burns without a visible flame, all you can do is use thermal imaging. How big, hot and bright is the object going to be? Link to comment Share on other sites More sharing options...
Ivan Tuzikov Posted February 5, 2016 Author Share Posted February 5, 2016 How big, hot and bright is the object going to be? Well, for example, a spacecraft, which can carry 1 living being (human, for instance) that starts from far side of the Moon, enters Earth atmosphere, lands, than launches and returns to the point of departure. Another hypothetic examples are: everything the same, except that the start takes place from the Pluto or Halley's comet when it is close to the Earth. I gave these description instead of calculations of size, temperature and brightness which I do not know how to perform correctly. P.S. I've watched the series Ancient Aliens several years ago and it sank into my mind. I've studied Wiki, some science sites and realized that the whole series is a mere pseudo-science. And now I try to find is there any scientific basis for speculations on alien visitations taking into account real physics (that is no FTL travel, wormholes, etc.) Link to comment Share on other sites More sharing options...
EdEarl Posted February 5, 2016 Share Posted February 5, 2016 Ivan, your question simple, but a complete answer is not. For example, that ship coming from the moon, does it have stealth technology that hides its torch as stealth airplanes owned by various governments on Earth, which hides them from detection here on Earth. If your torch ship coming from the Moon does have stealth technology, it would be very hard to detect, especially since any civilization that can make the trip across vast distances of space would be considerably more advanced technologically than we are. A simple answer is that distances are vast, and there have been no confirmed sightings of aliens. On the other hand, spy drones are shrinking in size, with limits probably smaller than a fly, perhaps nanometer sized. It is possible we are being watched, but if they are, they haven't tried to destroy us. And, it requires a very advanced and complex civilization the Occam's razor tells us that it is almost certainly not true. Link to comment Share on other sites More sharing options...
swansont Posted February 5, 2016 Share Posted February 5, 2016 Well, for example, a spacecraft, which can carry 1 living being (human, for instance) that starts from far side of the Moon, enters Earth atmosphere, lands, than launches and returns to the point of departure. If you watch video of the lunar lander leaving the moon, there is no visible plume. Link to comment Share on other sites More sharing options...
pavelcherepan Posted February 6, 2016 Share Posted February 6, 2016 For example, that ship coming from the moon, does it have stealth technology that hides its torch as stealth airplanes owned by various governments on Earth, which hides them from detection here on Earth. That's probably the least of the problems. Modern stealth technology is focused on hiding the plane from high-frequency radars, X-band and above. It's very hard to hide a craft from low-frequency radars. Radio telescopes, on the other hand use a wide range of frequencies and it would be very hard to shield an object from all of those. Link to comment Share on other sites More sharing options...
EdEarl Posted February 6, 2016 Share Posted February 6, 2016 That's probably the least of the problems. Modern stealth technology is focused on hiding the plane from high-frequency radars, X-band and above. It's very hard to hide a craft from low-frequency radars. Radio telescopes, on the other hand use a wide range of frequencies and it would be very hard to shield an object from all of those. Stealth technology on Earth is more advanced than x-band, an alien technology capable of interstellar travel must be much better. Wikipedia Stealth technology also termed LO technology (low observable technology) is a sub-discipline of military tactics and passive electronic countermeasures,[1] which cover a range of techniques used with personnel, aircraft, ships, submarines, missiles and satellites to make them less visible (ideally invisible) to radar, infrared,[2] sonar and other detection methods. It corresponds to military camouflage for these parts of the electromagnetic spectrum (Multi-spectral camouflage). Link to comment Share on other sites More sharing options...
pavelcherepan Posted February 6, 2016 Share Posted February 6, 2016 (edited) Stealth technology on Earth is more advanced than x-band, an alien technology capable of interstellar travel must be much better. I was talking particularly about stealth in respect to radio waves detection. Visual and infrared are a whole other story. ll current stealth aircraft were designed to counter X-Band radars, but those shapes are getting ineffective if a radar operates in S-band and even more ineffective when the radar operates in L-band. The reason for the stealth aircraft to be detected is the wavelength of the radar, a radar operating in L-band produces wavelengths with comparable size to the aircraft itself and should exhibit scattering in the resonance region rather than the optical region, so that most of the existing stealth aircraft will turn from invisible, to visible. http://aircraft.wikia.com/wiki/Counter_Stealth_Radar https://en.wikipedia.org/wiki/Low-frequency_radar Infra-red stealth for aircraft, is only possible from certain directions. You can't possibly hide IR signature when viewed from the rear. Edited February 6, 2016 by pavelcherepan Link to comment Share on other sites More sharing options...
EdEarl Posted February 6, 2016 Share Posted February 6, 2016 To move past radar cloaking, assume it cannot be done effectively. Aliens could send miniscule drones to spy on us in an asteroid shaped ship that appears to burn up on entry, but instead releases a ton of dragon fly sized and disguised drones to spy on us. Stealth includes many more technologies than radar cloaking. My point is that advanced alien technology can foil our technology, if they think it is necessary. Although, I believe aliens could hide from us, I believe it is unlikely we have been visited. Link to comment Share on other sites More sharing options...
Ivan Tuzikov Posted February 8, 2016 Author Share Posted February 8, 2016 Great thanks to everybody who participated in the discussion, but it seems that we digressed from the subject. Again, can somebody, who knows the history of astronomy answer me, at least approximately: at which point of astronomic observations (the year, or decade) was there enough number of Earth astronomers and telescopes to detect the incoming spacecraft by its exhaust plume during acceleration or deceleration? Link to comment Share on other sites More sharing options...
pavelcherepan Posted February 8, 2016 Share Posted February 8, 2016 Great thanks to everybody who participated in the discussion, but it seems that we digressed from the subject. Again, can somebody, who knows the history of astronomy answer me, at least approximately: at which point of astronomic observations (the year, or decade) was there enough number of Earth astronomers and telescopes to detect the incoming spacecraft by its exhaust plume during acceleration or deceleration? That really depends on the size of the ship. For example, as awesome as Hubble telescope is, it still can't see Apollo lander on the Moon and it's really close by. If the ship is not enormous in size you won't be able to notice it, because modern telescopes won't be able to resolve such a small object. Link to comment Share on other sites More sharing options...
EdEarl Posted February 8, 2016 Share Posted February 8, 2016 Great thanks to everybody who participated in the discussion, but it seems that we digressed from the subject. Again, can somebody, who knows the history of astronomy answer me, at least approximately: at which point of astronomic observations (the year, or decade) was there enough number of Earth astronomers and telescopes to detect the incoming spacecraft by its exhaust plume during acceleration or deceleration? You haven't given enough information to answer your question with a distance from Earth such a ship can be detected. Link to comment Share on other sites More sharing options...
Ivan Tuzikov Posted February 9, 2016 Author Share Posted February 9, 2016 OK, let's imagine for this mental experiment, that the size is similar to that of Apollo lander and the distance is: Earth surface - Earth Thermosphere. Link to comment Share on other sites More sharing options...
EdEarl Posted February 10, 2016 Share Posted February 10, 2016 Meteors that size are detected; thus, it is likely a ship that size in the thermosphere would be detected, unless they were trying to hide. If aliens are not trying to hide, it seems reasonable they would send radio signals telling us they were coming, and many radio telescopes around the world would receive their signal. My assumption is they would signal us long before we could see them. Otherwise, if they are trying to hide, we would not detect them because their technology must be very advanced. Link to comment Share on other sites More sharing options...
Moontanman Posted February 10, 2016 Share Posted February 10, 2016 (edited) I would have to say that such a small craft using the amount of energy required to land and take off the Earth would be a pretty big deal if it were propelled by non magical means. Hiding such an enormous energy signature would be very much like hiding the Saturn V Rocket both in landing and take off, nothing is free. Edited February 10, 2016 by Moontanman Link to comment Share on other sites More sharing options...
EdEarl Posted February 10, 2016 Share Posted February 10, 2016 If they didn't want to be seen, it is more likely they would send a disguised drone than a ship full of aliens. It seems unlikely they would intend to conquer a planet with one ship, unless they intend to use resources on the Earth, in which case they would probably be stealthy and send a drone. People will cross the street to spy on neighbors. Governments will send spies to other countries. However, sending a spy to another world doesn't make sense, since the important things can be learned by listening to our transmissions and watching us with telescopes. Link to comment Share on other sites More sharing options...
Ivan Tuzikov Posted February 10, 2016 Author Share Posted February 10, 2016 Well, was it possible for astonomers in developed countries in 1900 /1920 / 1940 (before the space era) to detect decceleration plume and atmospheric entry of a landing module holding 1 human (for example) that lands not farther than several hundred km from the populated areas? Link to comment Share on other sites More sharing options...
EdEarl Posted February 10, 2016 Share Posted February 10, 2016 Well, was it possible for astonomers in developed countries in 1900 /1920 / 1940 (before the space era) to detect decceleration plume and atmospheric entry of a landing module holding 1 human (for example) that lands not farther than several hundred km from the populated areas? Maybe. The first radio telescope was built in 1932. Radar was very new in 1940.Before 1908 there were about 50 relatively small reflecting and refracting optical telescopes listed in Wikipedia as operational in 1900. The 100" (2.54m) Hooker Telescope was built in 1918 and was the largest until 1948, when the Hale telescope 200" was built. The 100" started modern astronomy when Hubble found that the Universe was larger than the Milky Way. Infrared telescopes, capable of detecting head from a rocket engine, did not exist until about 1965. Amateur astronomers have found comets with small personal telescopes. Pluto was found in 1930 by one of the first astrograph telescopes, which are designed to photograph the sky; thereby, they allow astronomers to find comets, asteroids, meteors and planetoids. Astronomy was not well funded until after WWII, until the Cold War; thus, the likelihood of detecting an approaching ship was not high. The sky is large and ships are tiny. Link to comment Share on other sites More sharing options...
Moontanman Posted February 10, 2016 Share Posted February 10, 2016 (edited) Well, was it possible for astonomers in developed countries in 1900 /1920 / 1940 (before the space era) to detect decceleration plume and atmospheric entry of a landing module holding 1 human (for example) that lands not farther than several hundred km from the populated areas? It would be possible today to do that as long as the "ship" didn't have to take off again, objects of that size on a ballistic trajectory from out side the atmosphere hit the earth every day, I would imagine if it began to maneuver in some way it might draw attention. You did say in your original post that you expected them to take off and leave? That makes it a whole new ballgame... oops! Edited February 10, 2016 by Moontanman Link to comment Share on other sites More sharing options...
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