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The year is 2109 C.E my friends and I were caught in a space disaster when the spacecraft we're in broke apart during a daring escape from a patrolling spacecraft. We stole an antique cellphone (from 1999, in good working condition) from a space museum but our escape was interrupted and fortunately we managed to get into the escape pod and didn't get caught up in the explosion. The only emergency transponder in the escape pod isn't working probably due to the destruction of the spacecraft. Given the technology of 1999, is it possible for us to sent out a distress signal to alert the leaving patrol spacecraft?

Note: the cellphone was the most innovative product of 1999 money can buy.

The escape pod is not a Faraday cage we're talking about the future and the patrol spacecraft don't necessary be on a lookout for distress signal; please use these clues to your advantage.

If there is absolutely no way to transmit any man-made signal out, please state a valid reason why it can't be done.

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    $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – Monica Cellio
    Sep 25, 2016 at 19:40
  • $\begingroup$ You're better off with a CB, GMRS, or FRS handheld radio - No digital crap, CDMA, TDMA, or GSM stuff to make it extra challenging. $\endgroup$
    – user27844
    Sep 27, 2016 at 19:02
  • $\begingroup$ Did all your 2109 C.E personal communication devices fall off in the museum heist? $\endgroup$
    – Emilio M Bumachar
    Sep 27, 2016 at 21:02

19 Answers 19

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Assets

  • 1 obsolete piece of short range comms kit requiring a battery you probably can't charge

  • 1 slightly malfunctioning escape pod with up to date comms that isn't working but you're still alive

Current standards say the Mayday should be broadcast on VHF channel 16 (156.8 MHz). A 1999 phone, probably on 2g would likely use 900MHz (UHF). The slightly broken comms unit in the pod is probably using channel 16 or equivalent*. This is your first problem. The patrol ship will be listening in for signals broadcast on the mayday frequency. That's the frequency you need to hit, so first up is rebuilding your phone to that frequency.

Or you could look at the pod comms system and see what's wrong.

Your next problem is that your mobile phone's range is laughable in interstellar space. What's going to be even more laughable is when you try to use it in the radiation shielded environment of your escape pod. The signal, which is line of sight at the best of times, most likely won't even penetrate the hull. So now you need to hook it up to the external antenna used by the pod's own comms system.

Or you could look at the pod comms system and see what's wrong.

Now you need to make sure you're using the right broadcast method: are you on AM or FM? (There's no reason to think that 100 years from now they'd be able to pick up an analog signal)

I'm sure you can see where I'm going with this. Fix the pod.

Ultimately all you're going to do is rebuild a copy of the pod's own comms system with a batch of obsolete components. If you're good enough to do that you're good enough to fix the pod's own system which will be much easier.

*I mention channel 16 as an example to show that there are standards for distress signals and they're very different from the standards for mobiles, if you want someone to pick it up then you need to be broadcasting on a frequency they're listening on.

Distress frequencies

2182 kHz forms an essential part of the Global Maritime Distress Safety System (GMDSS). It has an associated DSC frequency at 2187.5 kHz. Other international distress frequencies, in use as of 2008, include:

121.5 MHz - civil aircraft emergency frequency
243 MHz - military aircraft emergency frequency
156.8 MHz - Marine VHF radio channel 16, short range maritime use
406 MHz / 406.1 MHz - Cospas-Sarsat international satellite-based search and rescue (SAR) distress alert detection and information distribution system

Discontinued frequencies

500 kHz Morse code is no longer monitored.
121.5 or 243 MHz locators. (No longer automatically monitored by satellite, though still used for aircraft communication and short-range direction finding.)
Effective 1 August 2013, the U. S. Coast Guard terminated its radio guard of the international voice distress, safety and calling frequency 2182 kHz and the international digital selective calling (DSC) distress and safety frequency 2187.5 kHz. Additionally, marine information and weather broadcasts transmitted on 2670 kHz terminated concurrently.
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    $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. Separatrix, please consider editing clarifications from that comment discussion into your answer if you haven't already. $\endgroup$
    – Monica Cellio
    Sep 25, 2016 at 19:41
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Absolutely. Simply write "S. O. S." on a piece of paper, wrap it around the phone, secure it with some tape or a rubber band, then put the phone in the air lock and open the external door. Now all you need is a deck of cards so you'll have something to do while you await rescue!

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    $\begingroup$ Brilliant! I like this answer. $\endgroup$
    – user64742
    Sep 22, 2016 at 19:48
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    $\begingroup$ The most productive use of the cell phone might be to see if it has a copy of Snake on it, or even Solitaire. If it has a text editor, you could even write your memoirs using the keypad. $\endgroup$
    – DawnPaladin
    Sep 22, 2016 at 20:37
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    $\begingroup$ If he OP is lucky and it's a flip phone, the paper could be placed inside it, with the tape and rubber bands on the outside. $\endgroup$
    – jpmc26
    Sep 22, 2016 at 22:24
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    $\begingroup$ This somehow reminds me of "How can you determine the height of a building with a barometer?" - "Ask the janitor, he should know it. If he is unwilling, bribe him with the barometer." $\endgroup$
    – Hagen von Eitzen
    Sep 23, 2016 at 11:36
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    $\begingroup$ Bad idea. If the only games you have are on the cell phone, now you've thrown away your only entertainment while waiting for rescue. $\endgroup$
    – Jay
    Sep 23, 2016 at 22:08
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I vote yes.

A lot of the cellphones back then already had a camera and flashlight. Actually the flashlight in those phones is often just a bright light, it doesn't even flash.

With that light you can easily send an S.O.S. signal.

And that's technically sending a signal out of your spacecraft. (It needs windows though.)

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    $\begingroup$ This is the only meaningful "yes answer" I found until now :) $\endgroup$
    – Noldor130884
    Sep 22, 2016 at 12:43
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    $\begingroup$ Pretty sure the diffusion of light would obviate any chance of detecting it by a patrol ship any real distance away. $\endgroup$
    – Nathaniel Ford
    Sep 22, 2016 at 16:46
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    $\begingroup$ @Pieter B "A lot of the cellphones back then already had a camera and flashlight." Can you give some proof to back that claim up? In my recollection of 1999, most of the phones had tiny black and white screens and were many years away from ubiquitous cameras. $\endgroup$
    – AndrejaKo
    Sep 22, 2016 at 18:19
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    $\begingroup$ The Nokia 3210 was top of the line for 1999 and very popular. It had no camera and no flash. If it did, most cell phones had no built in option to use the flash as a flashlight, but I suppose they could take pictures with the flash on. But the rescuing spacecraft wouldn't see it because distances in space are measured in hundreds of kms. As your distance doubles, the intensity of your light drops by 4. Put another way, do you think you'd see a cell phone flash from 100 km away? Also escape pods would have blinky lights for exactly this purpose. $\endgroup$
    – Schwern
    Sep 22, 2016 at 19:26
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    $\begingroup$ @Schwern - the Nokia 3210 was never "top of the line". It was popular because it was a budget phone and had a wider variety of replaceable covers available for it than any other. That said, the 8210 which was top of the line at the time also lacked a camera. It did have an irda port, however, which might produce detectable (albeit non-visible) light in some circumstances. $\endgroup$
    – Periata Breatta
    Sep 22, 2016 at 20:51
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No. The cellphone is not a general-purpose radio transmitter, and without a signal from a base station (the kind that exists in every cellphone tower) it won't send anything except the "hello, any base stations out there?" signal.

Modifying it to do anything else is impractical: it's built to operate with a base station network, and the logic of doing that is built into its chips. The manufacturers wanted it to be hard to hack, because doing so would allow malicious users to mess up the cellphone network.

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    $\begingroup$ I doubt the phone would even send a "hello" signal before detecting the base station existence. See slide #2 of this presentation: slideshare.net/KannanSelvam1/gsm-signaling So, the 100 years old phone without the accompanying infrastructure is just a brick. $\endgroup$
    – szulat
    Sep 22, 2016 at 13:18
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    $\begingroup$ @Crowley Yes, most of the energy is used on passive listening! (compare the energy-hungry gps, which is a pure receiver) The active phone reports its availability to the current station every few hours and only listens for 99,9% of the time. The actual "searching" is passive, then the phone contacts the best station but without a nearby station there is nobody to contact and the phone would not transmit anything. $\endgroup$
    – szulat
    Sep 22, 2016 at 18:10
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    $\begingroup$ GSM phones can't send anything until they have received something. GSM used time division multiplexing, where different phones use "timeslots" (a small time interval during which they are allowed to transmit without affecting others on the same frequency). Since this: (a) requires the base station (the cell tower) to allocate a time slot, and (b) is dependent on distance from the base station (due to propagation delays), it can't send anything unless it did indeed receive a signal. Note that scanning may be passive, but it still requires some energy to decode the signal etc. $\endgroup$
    – jcaron
    Sep 22, 2016 at 21:45
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    $\begingroup$ Maybe the manufacturer of that phone forgot to test such condition and the phone entered some busy waiting loop, wasting the energy? Or it was receiving a (weak) base station signal and was constantly trying to establish two-way communication (and failing), which would indeed cost a lot of energy. "Blind transmissions" simply make no sense in GSM. $\endgroup$
    – szulat
    Sep 23, 2016 at 0:15
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    $\begingroup$ @szulat Any cell phone will have some sort of RF amplifier that it uses on the incoming signal. When the signal is weak or absent, it turns up the amplifier to try to pull something in -- using more power. When there's a strong signal present, it can turn down the amplifier, using less power. $\endgroup$
    – user25661
    Sep 23, 2016 at 22:03
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A cellphone from our era transmits with a power between 0.6 and 3 watts. For comparision, the Voyager probes had a 12 watt antenna. To succeed, the Voyager had to aim its dish at Earth and large radio telescopes on Earth were needed to receive the feeble signal.

If the transponder's dish isn't broken and can be pointed to likely craft locations, a cellphone may therefore produce enough power for a signal, even if it's gibberish. A cellphone will usually max out its transmissions power when searching for a base station.

Aiming at a large radio telescope somewhere would be better than broadcasting aimlessly. If you can transmit to Earth when your pod passes directly between say, Earth and Mars with it colonies, a lot of radio telescopes on Earth would already be aimed your way.

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    $\begingroup$ Except that antennas are not ultrabroadband, and the difference between a normal cell phone antenna and an "interstellar one", let's say for communications from Earth to Mars, are optimizations: a couple of GHz vs. a couple of tenths of GHz. $\endgroup$
    – Noldor130884
    Sep 22, 2016 at 12:40
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    $\begingroup$ From what I know, mobile phone will never transmit anything blindly, it has to synchronize its signaling with the correct timeslots dictated by the base station, otherwise it would disrupt the other phones' communication. This means that our hypothetical phone taken away from the earth would not send any signal because it would not be able to find and synchronize any base stations. See also: slideshare.net/KannanSelvam1/gsm-signaling $\endgroup$
    – szulat
    Sep 22, 2016 at 13:34
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    $\begingroup$ But Voyger have focused antenna (dish). I've never seen cell phone with "satellite dish". $\endgroup$
    – Crowley
    Sep 22, 2016 at 18:35
  • $\begingroup$ I find this answer ideal because it actually compares against real requirements by looking at what an existing space-faring communication system had to do. $\endgroup$
    – Cort Ammon
    Sep 23, 2016 at 0:42
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Here is a top-of-the-line 1999 phone, apparently the first to feature a WAP browser: https://en.wikipedia.org/wiki/Nokia_7110

No flashlight (high power white LEDs not having been invented yet). The phone is either a GSM or a TDMA model. Either way, it is an omnidirectional transmitter in the 900 or 1800/1900 MHz band.

When you turn on the phone, it looks for a network. If it finds no network, that is pretty much the end of story; it will display an error message and will continue to search for a non-existent base station.

Modifying the phone is not an option. Even if you had the right documentation and tools at your disposal, you are confronted with a small circuit board with numerous densely-packed surface mount components, and in any case, those components are custom-designed to connect to a cellular network, they are not general-purpose radio chips, for instance.

So I think your best bet is to take out the phone's battery (I assume it is in good working condition and charged), find some lose wiring, and try to build a spark transmitter. It is a horrible abuse of the battery, but it just might work... especially if you can also fashion a crude parabolic dish and aim it at your potential rescuers. Even so, unless your rescuers are a) nearby, and b) are aiming a parabolic dish at your direction, it is very unlikely that they will receive a signal... your SOS will basically disappear in the noise.

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What a coincidence! I'm also from the year 2109 and that was MY museum you ripped off! I want my phone back. Wife misses it. Frankly, thieves deserve that fate of yours.

However, if I were in a giving mood, I might suggest another approach. My cellphone is omni-directional and is not meant to broadcast far. I don't remember precisely, but it MIGHT have an LED on the top. LED's are coherent light and experience much slower power dispersion than an omni antenna. Of course, you would have to know where to point it. You could easily rig a circuit to modulate the LED to send an SOS and other info ... if you have the know-how. Think "fiber-optics" without the fiber. Put several of these together and you have a little array of lasers which is more likely to be detected.

How far are you trying to send the signal? Light is very fast, but if you're in another galaxy, or even another solar system, forget it. Both dispersion and light travel time will mean you're stranded forever. A fitting end for theives, hmm?

I'm not up on current events, but we might have inter-planetary or Star Trek-esque subspace relays off of which you could bounce a signal and minimize dispersion.

Tell you what, keep the phone. Just let me know the hot stocks for the next 30 years.

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    $\begingroup$ LEDs are not coherent lights. Laser LEDs are, but incidentally I've been the original owner of that phone until you stole it from me for your museum. And I can tell that it was not a Laser LED. $\endgroup$
    – Stéphane Gourichon
    Sep 23, 2016 at 14:25
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Yes, because of FCC test modes

A lot of people are assuming that a cell phone can only talk to a cell base station. If you are constrained to the end-user interface that is true, but if you can use your 100-year-future version of today's JTAG pod to get inside the firmware, the hardware itself will have been capable of transmitting an umodulated carrier at various frequencies during regulatory testing, and you can use that to send a slow Morse Code call for help. Then it's only a question if someone happens to be listening on a frequency you can reach; with luck some of the phone's frequency range will have become a ham band in the intervening years (and maybe someone is known by that community to be a on DX-pedition to an asteroid in your general direction, causing high-gain receive antennas to be pointed your way)

It's theoretically possible that test modes on this level could be accessible from the keypad, especially as an oversight (lots of products have shipped with test modes someone forgot to take out, or maybe the phone's state gets corrupted by a cosmic ray, exposing something not meant to be exposed)

A downside is that you won't know your signal has been received, until the rescue arrives.

It may go further than you think

We're used to thinking of handheld radios as having a short range, because signals may not readily wrap around the earth's horizon, clear obstacles, etc, and when they marginally do higher transmitter power can help. But conditions of good ionospheric reflection you can communicate around the earth on a few watts. And with line-of-sight in space power is even less of an issue.

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Yes you can. However, the signal strength would be weak considering it's a cell phone and the range rather poor. Considering all the interference which could obstruct you (wall, other frequencies, magnetic fields, solar flares etc) your chances of reaching a receiver are close to zero unless it is in close proximity and actively searching for a signal.

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    $\begingroup$ for a signal in the cell phone's frequencies... $\endgroup$
    – Noldor130884
    Sep 22, 2016 at 12:34
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    $\begingroup$ This represents an almost complete misunderstanding of radio communications and the space vs. terrestrial environment. $\endgroup$
    – Chris Stratton
    Sep 23, 2016 at 21:58
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Create a Giant Antenna

Given that your pod components are somehow damaged-beyond-repair, remove all the reasonably-strong wire you can from it and splice it all together. Splice it into your cell phone's antenna (assuming that is the only source of power). Tie one end of the antenna to something heavy and heave it out the airlock with as much force as you can in the direction opposite the travel of the pod. (This will be tricky.)

Now, your cell phone has way too little juice to really make this matter, but it will serve as well as anything else for sending some signal down the antenna - even better if that signal, regardless of it's content, can be in the Morse-code short short short, long long long, short short short format. No encryption is needed for that. Failing that, any repeated signal will do as that is almost certainly man-made.

More importantly, if the rescue ship is doing any active scanning at all, being The Future and the computers are better, it should twig to the fact that there is an antenna - which will cause an anomalous interference with signals in a distinct 'line' pattern along the length of the antenna. If the computer knows that such an antenna shouldn't be there, it should flag it as maybe worth looking at. The longer the antenna the more likely that active scans (read: throwing various beams of light at various frequencies out) will pick up the anomaly. Energizing the antenna at a rhythmic pace will give the computer additional clues as to the fact what it is looking at is man-made.

Of course, if the amount of debris is too high, or there are a lot of signals bouncing around, this may be way too small a difference for anyone to really notice.

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I think the your best option would be to re-use available gear to create a spark-gap transmitter. As it works more like a radio jammer than well-behaving transmitter, you might interrupt someone's regular radio conversations ;)

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Yes

I vote for yes. Cell phones back then used to have huge batteries. You might be able to rig something up to transmit some kind or morse code just through electromagnetic interference noise.

How much power you can generate depends on how much wire you have and how much electrical current you're prepared to sacrifice.

Electromagnetic Interference

Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data. Both man-made and natural sources generate changing electrical currents and voltages that can cause EMI: automobile ignition systems, cell phones, thunder storms, the Sun, and the Northern Lights. EMI frequently affects AM radios. It can also affect cell phones, FM radios, and televisions.

EMI can be used intentionally for radio jamming, as in electronic warfare.

As right pointed out by another answerer, your ship will have shielding to protect the occupants from external radiation/electromagnetism. You're going to need to somehow shove that transmitter out of the airlock but still have control over it.

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    $\begingroup$ You must have built a radio else that's very cool. $\endgroup$
    – user6760
    Sep 22, 2016 at 7:46
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    $\begingroup$ Hahaha the electrons from your coils vibrates at a random freq must have interfere with the TV signal, it is difficult to control the energy of the electrons to emits legible radio signal. $\endgroup$
    – user6760
    Sep 22, 2016 at 7:53
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    $\begingroup$ 1999 technology "huge batteries" which haven't been charged in over 100 years would be holding about as much charge as the brick the 1999 phone resembles. If you want power you'll be better off trying to hack into your pod's electrical system. $\endgroup$
    – brhans
    Sep 22, 2016 at 17:47
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    $\begingroup$ The "something" you would rig up is called a spark gap transmitter. It radiates broad spectrum EMI. A spark gap needs a high voltage such as can be generated using a car's ignition coil. If the pod has an ignition coil, you're in luck. $\endgroup$
    – Wayne Conrad
    Sep 22, 2016 at 17:53
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    $\begingroup$ This is conflating "large in size" (which they weren't) with "has lots of power" (which they didn't). Using the Nokia 3210 for reference, it had a 1250 mAh battery. The modern Nexus 6P has 3450 mAh. For reference, a AAA battery has 800-1200 mAh. Also the battery is 100 years old and probably lost most of its ability to hold a charge. $\endgroup$
    – Schwern
    Sep 22, 2016 at 19:18
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Some things to consider:

  • Is the cell phone still working? (Phones were pretty sturdy these days, so probably yes)
  • Is the battery still working? (Alternatively you should be able to find a low voltage output somewhere in your pod, lets count this as yes as well)
  • it would use GSM (2G) or UMTS (3G, if you are very lucky). Is this (still) supported on a planet near to you, additionally: is is a multi-band phone?
  • Base stations, which you need for the connection are unlikely to transmit omni-directional, since they are made for surface dwellers. (I haven't tried to use my phone in a plane, but I suppose you would have a hard time to connect above 10 km height.
  • you are likely to move rather fast relativ to a planet, even if you get the base stations, will they be able to hand you from one cell to the other? Related: digital radio (DAB) is said to get problems beyond 200 km/h (?), is there a limit for cell phone connections as well)
  • Cell phone use omni-direcional antennae, additionally the signal is not very strong. You should consider building a high gain directional antenna (For wlan, there are some designs using foam and blank wires)
  • cell phones transmit a digitally coded signal, i.e. unlike analog radio, you can't just listen in even if you manage to get a signal to a planet.
  • there are some problems with the GSM protokoll if you cant log into a base station.

As it can be seen, there are some problems in using a cellphone in a normal way in space. it might be easier to get a continuous carrier signal out of the phone (just 900Mhz or similar), try to build a directional antenna and use it for Morse code (signal on/of) in the direction of the next planet with a receiver.

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Definitely not!

It is not possible today; even your cell phone in orbit around the Earth gets the signal from the ground. The signal is probably not strong enough to reach 200-300km altitude, but to point out the main problem let's say that it is possible. (Actually, I will be not so surprised if cell phone could recognize the signal from BTS for 200km range.)

The main problem:

Even if the signal is OK and the phone can "see" a BTS and a network, the problem for GSM, as it has been mentioned already, is time slots.

Time slots limit the effective distance to 35km only.

This limited the original range of a GSM cell site to 35km as mandated by the duration of the standard timeslots defined in the GSM specification. The maximum distance is given by the maximum time that the signal from the mobile/BTS needs to reach the receiver of the mobile/BTS on time to be successfully heard. At the air interface the delay between the transmission of the downlink (BTS) and the uplink (mobile) has an offset of 3 timeslots. Until now the mobile station has used a timing advance to compensate for the propagation delay as the distance to the BTS changes. The timing advance values are coded by 6 bits, which gives the theoretical maximum BTS/mobile separation as 35km. Wiki

In other words when your phone gets a slot to speak, "now is your time to go", the response from your phone reaches the BTS too late to make a connection or to transmit data. GMS voice is just data transmission. If you were to boost your mobile phone signal, and the BTS had big gain antenna, you would almost hear the signal (as nonsense :) ), but your GSM phone will still be not able to work for a greater distance than 35km.

Recommendations:

  1. You can replace old GSM phone from 1999 with some archaic professional "walkie-talkie" which don't need any BTS or network infrastructure, don't emit the signal in quite complex modulation, are packed to the small data sets and also encrypted with a key received during 1st three-way handshake when your phone connects to the GSM network. But keep it professional, because consumer walkie-talkie is not powerful enough. The signal power is limited for civilian devices to a city band.

  2. Instead of your guy's old GSM phone, try an old radio frequency transmitter. They need to power it somehow because the battery is dead, because it is an old device. So they find that they need, to simplify, 12V. There is an external 12V source plug.

    In the spaceship there would be a lot of working devices. So they disassemble the main panel and try to find supply cables. From the power source of the panel, they power up the transmitter. (The assumption is that for powering electronic devices the supply power is usual 12V, so the panel and its units could be supplied with 12V; not the chips on the circuit board, they are about 5V or 3V, but units.)

Meanwhile on the Earth, there is a group of young students with their teacher just finish assembling a simple amateur radio receiver and they are trying to test if it is working. But something is disturbing the reference test signal in the lab ...

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I don't think you can, based on the simple fact that you might get lucky and grab a walkie talkie, which was popular around that time to build into a phone, (The ranges I see got for that are in the range of 30 to 40 miles. Low Earth Orbit is around 100 miles up.) the more likely event is that you get your hands on a Nokia 3210 or maybe a Nokia 9110 which doesn't even have that possibility to reach LEO it seems, but their batteries, provided they work, have around 4 Wh of power so, yay...

Probably, a much better use of your time is to look for any object that can be used to focus light or produce a laser and use the battery of the phone to power that to send an SOS in morse code using the light. That might even be how we communicate then anyways and all you'd have to do is figure out where to point the thing and send a coherent message. In that case, you would need to just write a program that very rapidly turns on and off the laser to convery the binary keyboard inputs into binary and flashes of light. Then you'd have a real time one-way communication and be able to request help very easily at that point.

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    $\begingroup$ You'd be lucky if your 1999 battery which hasn't been charged still has even the tiniest amount of charge in it. Certainly many orders of magnitude less than 4Wh. $\endgroup$
    – brhans
    Sep 22, 2016 at 17:49
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    $\begingroup$ Now that you're mentioning walkies-talkie ranges, well, things work a bit different in space. A cell-phone with let's say 8 W transmitter (highest power fro GSM according to my sources), in space, that tries to connect to a base-station that is also in space and has say 15 dB of antenna gain, would have arange of 5-6 Mm, not just a handful of miles we have on Earth. $\endgroup$
    – AndrejaKo
    Sep 22, 2016 at 19:10
  • $\begingroup$ Yes, the signal will go far. The muxing protocol may choke on the propagation delay though! $\endgroup$
    – Chris Stratton
    Sep 23, 2016 at 21:45
  • $\begingroup$ @AndrejaKo interesting. Did not know that... though it depends if you're on a planet or in space, I would guess due to atmosphere? If that's the case then if you're on the Moon vs on Mars the situation would be different too. $\endgroup$
    – Durakken
    Sep 24, 2016 at 7:45
  • $\begingroup$ @Durakken There is some attenuation due to the atmosphere, but in usual cell-phone calculations, it's considered to be 0, for simplicity (I hear that radar people do actual modelling on that). THe biggest issues are reflections. If you want to look things up, search for Friis transmission equation, which models space-ships with no obstacles nearby, and two-ray ground reflection model, which models communication on infinite, flat, reflective plane. Just the first reflection can cause significant range shortening. $\endgroup$
    – AndrejaKo
    Sep 24, 2016 at 12:58
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Well as many gave noted here the cellphone is pretty much useless unless you do something. Since its hardwired to transmit a signal looking for towers nearby all it can do is that and you have to work with it. All you can do is give it a boost so it talks louder not different.

You cannot make 1999 technology do the work done by 2100 technology, but you can modify 20th century technology so they simply do better what they did before.

Remember you want to get rescued here, not reinvent the cellphone all over again, hence all you have to do is create a commotion, one of any kind, even one which is a loud "HELLO IS ANYONE THERE" signal.

Maybe your friends know basic engineering:

1.) Add external antenna to give cellphone boost in the unheard of levels

2.) Give the cellphone an unhealthy kind of power supply, make this thing rock whole planets (a figure of speech)

3.) Turn on all lights / camera flash / accessories when sending it out in a probe

4.) Send out a ping signal along with constant text messages everywhere asking for help maybe even a picture

5.) Put it all in a box and send it out with high hopes that someone notices it before it blows up

Remember, this isn't about safety or efficient design, its about a group of survivors who throw in their last ditch effort at being rescued. They don't want this drone floating around forever in space, because they wont survive forever, hell they're hoping it makes some noise,a large amount of noise given their predicament and lack of equipment for a short period of time before it burns out and then luckily get rescued by some ship which happened to notice this antique cellphone kinda signal from the 20th century because they happened to have an expert in their crew who noticed it. Why? Well the protagonist's dumb luck I guess

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100% Yes

Remember Morse code. You don't need much to make that work. So Take your cell, figure out which way you want to go. Either rework the radio bit to send out "something" (even static), or ditch the radio bits and use the lights.

Remember you don't need much to send Morse code.

Now as to having that signal be received, well. With the radio part the receiver would need to be "tuned" to the correct frequency. It has to be listening somehow. Even if your only managing to modulate static, someone has got to be listening to the static.

For the light, that's even more of a crap shoot. Someone or something need to be looking. That cell phone light isn't going to travel very far.

You might better spend your time making the port side spot light blink.

TL;DR sure you can use it to send a SOS. Rather it's received or not....

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Biggest problem would be the people figuring out how to use it. They did a test a few years ago, and people couldn't even figure out how to turn on an old computer, let alone use it. NASA couldn't even build a saturn V rocket if their life depended on it. We can't build a flying Write Brothers airplane either.

Having been using zero point power cells for the last 50 years, the concept of a battery would be so foreign to them they would be stumped. The very idea of dc current would be like speaking chinese to a kenyan president. Everyone knows electricity is just used to to wow children in magic shows because it has no state or need to traverse along paths.

Besides, what if the raygun happy cops hear your SOS and tell you to drop the phone, and because sound doesn't travel in space you don't hear them. Rioting and burning the sun down would ensue.

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You absolutely can send any signal from the ship. Anywhere.

The trouble is, that intensity of the signal, and thus signal-to-noise ratio, decays with the factor 1/r2, where r is the distance.

So, without network that will transmit (receive, amplify, send) your S.O.S. signal none can hear it.

Shouting out loud will have the same effect...

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  • $\begingroup$ And in space, no one can hear you scream. $\endgroup$
    – JAB
    Sep 22, 2016 at 16:15
  • $\begingroup$ @JAB Neither your scream, neither any signal you send, if they are far enough (unless amplified). $\endgroup$
    – Crowley
    Sep 22, 2016 at 16:36

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