Measuring mass in space

[rgrove0172]

"Sir, Im detecting a 105kg variance from my initial mass scan when we took on frieght. I think we might have a stowaway"

How would a ship determine their wieght in space? Without gravitic technology, how would an orbiting ship determine how much a pallet of goods wieghed if it was packaged in orbit as well? We would have to subject the object/section of the ship to gravity would we not?

So in the quote above, the cargo area would have to be in spin gravity in order for the tech to determine the variance in cargo weight. If it was in a gravity free area, there would be no way he could tell, could he? With TL9-10 technology?

hmm, just had a thought.. could you use the effect of your maneuevering thrusters? Measure the velocity after a 10 second burn or whatever and compare it to known effects with given mass? In this way if your ship moved .00034 meters slower than it did at your believed mass, you would know you had some unaccounted for weight somewhere, couldnt you?

 

[BytePro]

You're mixing mass and weight - the former is a property of matter, the latter is a measure of acceleration acting upon it.

... how would an orbiting ship determine how much a pallet of goods wieghed if it was packaged in orbit as well? We would have to subject the object/section of the ship to gravity would we not?

Change that to 'subject ... to a known force' and you have your answer.

So - yes - you could use your thrusters (a known force) to determine what your mass is assuming you know the dynamic directional external forces - i.e. n-body gravity - also acting upon your ship as well as its expected performance and are able to accurately enough also measure the distance traveled in a given time.

 

[rgrove0172]

Awesome, I need that little discovery in a plot line Im working on. Thanks!

 

[shaunhilburn]

"Sir, Im detecting a 105kg variance from my initial mass scan when we took on frieght. I think we might have a stowaway"

Stutterwarp computers could easily detect that kind of discrepancy.

 

[BMonnery]

Stutterwarp computers could easily detect that kind of discrepancy.

How? The computers aren't doing quantum calculations (such things are impossible), they're controlling the drive somehow which is a bit like a modern high performance turbine is controlled by a computer.

Now, the drives are pushing slightly more mass, and so tunnel lengths are shorter (less than 0.1% though) which translates as about an extra 2 minutes on an interstellar journey.

This is probably less variance than minor flutuations in the power grid or perhaps local gravimetric phenomena.

For a stowaway the dead giveaway will be their lifesigns, CO2 levels increasing in certain compartments for example.

Spotting stowaways will be important as the classical "space pirate" is essentially impossible in 2k3 (regardless of the not quite canonical Challenge articles). If you have an armed ship and wish to make money the only way of doing it is really running a protection racket, and even then it's a lot easier to threaten sabotage in dock.

As an exercise, it would take a "catch" ship 37 hours of continual weapons fire on average to stop the victim (drive or computer hit), during which far more hull damage than an freighter could absorb would be inflicted, and any patrol vessel in the area would have slagged the attacker.

However, the most valuable thing about a starship is the starship itself, not the cargo. To seize a starship you want to put people onboard, either as passengers with concealed weapons or as stowaways. The other option of course is to sabotage the ship (for example, insert a virus into the ships computer or put a robot in our "cargo") and then have another ship be "rescuer", with the "rescue team" boarding with armoured hardsuits and plasma guns.

 

[shaunhilburn]

How? The computers aren't doing quantum calculations (such things are impossible), they're controlling the drive somehow which is a bit like a modern high performance turbine is controlled by a computer.

There is a projected warp performance based on payload manifest, fuel load, etc. It's a known quantity.

An 80 kg stowaway is a 0.08 ton discrepancy between that predicted performance vs the measured actual. It should be detectable in the input power vs tunnel length. If the computers sense the vessel isn't tunneling as for as it should, then something's amiss.

 

[shaunhilburn]

Assuming the equipment can resolve tunnel length to part-per-million (millimeters) accuracy.

 

[rgrove0172]

I can buy that, perhaps not in the way of a "Broooooop Brooooop.. Warning Warning - a variance in the warp performance has indicated a possible discrepency in the ship mass! Brooooop Brooop" But if one of the techs was running a diagnostic or something, or maybe just monitering closely it might show up as a "hmmmm"

Your right of course about life support being the dead give away.. my thought was that the stowaway was in the hold however, probably not pressurized and thus in a suit on their own air.

 

[BytePro]

Even ignoring fictional drives - calculating actual mass at least at departure/launch - would probably be SOP.

In the RW, plenty of intended space vehicles have been self destructed because of mistakes in software/data related to assumed mass. Metric conversion mistakes related to assumed mass have also resulted in the loss of space probes (Mars).

Constant, automatic, navigation updates would expose an issue of unexpected propulsion performance change while in flight... which, depending on tech, would directly or indirectly implicate unexpected mass.

 

[rgrove0172]

I see your point. If its not a mass issue, then something is wrong with the drive... so it would need to be checked out. Thanks!

Oh and I read about the probe mess. God I would hate to be that guy.

 

[McPerth]

I agree with BMonnery that the easiest way to be detected, it will be easier by CO₂ emisions (unless he's in a p-suit, but how long can one live inside it?), heat, etc...

This measurement of performance (that could call into attention of the crew if sustained along all the trip, so discarding local gravitationary effects, power grid fluctuation, or so ,that will probably not be sustained) could be more useful to determine if the cargo is really what the registry says (Hey, if the carge we carry is grain, how can it be so heavy?).