Questions regarding Grav technology

[GamerDude]

Well I think your specific question and the way we understood the initial post are pretty close...

How strong of a gravity field is needed for grav vehicles to work? Well how high could an air-raft get above the surface of the earth, measure the gavity field there and BANG the answer.

So really a question is how high above earth can an air-raft get?

 

[BP]

Good question. Here's my take:

The Air/Raft desc in Core uses 'supported by anti-gravity technology'. Unless one is operating in a non-gravity environment (i.e. anti-anti-gravity) then since it is opposing any gravity and adding extra force (to accelerate, manuever and maintain upto x speed) it doesn't neccessarily have any appreciable limits. So, if it is pulled by 2 G then the craft uses the 2 G to repulse that pull. (Kind of like a small child can throw a large adult across a room - it is not the force of the child, but the redirected force of the adult that can allow this to happen). At this point the net forces cancel out so that no greater energy must be expended for other operations. Occupants however, would still feel the full Gs plus any forces due to accellerations...

Being typically manned - some practical operating limits would exist. Most people would blackout over 5 Gs without some kind of compensating tech. For air/rafts, grav belts and the like this would probably be unlikely.

One isn't like to be alive for other reasons if attempting to leave the surface of a gas giant

In other words - not sure there are any limits that would need to be directly accounted for as other factors would likely apply first.

 

[BP]

...So really a question is how high above earth can an air-raft get?

(Sorry, I missed your post that beat my last...)

Core states 'can even reach orbit' which is pretty loose (LOE or the moon's orbit?).

My take is that it uses gravitics like a spacecraft for acceleration, and contra/anti grav to negate the exisiting gravity. The former would technically allow it to travel between planets - but at 400 kph - the closest direct distance to mars in the last 50,000+ years being over 55 million miles - so in over 15 1/2 years I think other things could be limiting (food/air) :wink: (Moon is >350,000 km IIRC - so well over a month to reach the moon).

In other words - like starships in MGT - I don't see the 'propulsion' as anti-gravity per say. For vehicle/personal devices (and possibly starships) anti-gravity comes into play to negate the existing gravity.

I'm sure there are holes in this - I haven't really given it much thought (since this is one of the more handwavium areas...)

 

[GamerDude]

...So really a question is how high above earth can an air-raft get?

(Sorry, I missed your post that beat my last...)

No problem, it happens.

Core states 'can even reach orbit' which is pretty loose (LOE or the moon's orbit?).

I quoted earlier (or thought I did) that there's a table in the Core book that lists an altitude of 10,000km for stuff, and gives as an example of that as "Surface to Orbit"

I found this article http://en.wikipedia.org/wiki/Orbit

 

[BP]

...I quoted earlier (or thought I did) that there's a table in the Core book that lists an altitude of 10,000km for stuff, and gives as an example of that as "Surface to Orbit"

Oh - I believe you did (its the Transit times table)... but then at 400 kph for an Air/Raft that is a 25 hour trip in a vacc suit - which typically only has 6 hours of air!

I read the 'can even reach orbit' as a statement of capability of the vehicle - that doesn't limit it to that range. On the other hand, the Grav Floater states '...like an air/raft, achieve any altitude up to orbit.', which could be construed as an upper limit or again just saying that it can reach orbit without laying down an absolute maximum.

In any case, unless one was trying to use it between spacecraft, say in orbit, the question becomes mute due to life support issues (and even in this situation there is no real protection from orbital objects that are flying at orbital speed - and from radiation belts and ion storms!).

The final answer is, of course, whatever the Ref decides

 

[GamerDude]

I went and did some more "Wiki-ing" and found two pages

http://en.wikipedia.org/wiki/Low_earth_orbit
http://en.wikipedia.org/wiki/List_of_orbits

The first page has LEO
A low Earth orbit (LEO) is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km. Given the rapid orbital decay of objects below approximately 200 km, the commonly accepted definition for LEO is between 160 - 2,000 km (100 - 1,240 miles) above the Earth's surface.[1][2]

With the exception of the lunar flights of the Apollo program, and the sub-orbital flights of the Mercury program, the aborted Soyuz 18a mission and the X-15 and SpaceShipOne rocket planes, all human spaceflights have been in LEO, including all Space Shuttle and space station missions. The altitude record for a human spaceflight in LEO was Gemini 11 with an apogee of 1,374.1 km.

The second lists various orbit classifications.
* Low Earth orbit (LEO): Geocentric orbits ranging in altitude from 0–2,000 km (0–1,240 miles)
* Medium Earth orbit (MEO): Geocentric orbits ranging in altitude from 2,000 km (1,240 miles) to just below geosynchronous orbit at 35,786 km (22,240 miles). Also known as an intermediate circular orbit.
* Geosynchronous Earth orbit (GEO): The orbit around Earth matching Earth's sidereal rotation period. All geosynchronous orbits have a (semi-major axis) of 42,164 km (26,199 mi).[1]
* High Earth orbit: Geocentric orbits above the altitude of geosynchronous orbit 35,786 km (22,240 miles).


So, seeing all this I'd say 200 to 300 km is "orbit"

What do y'all think?

 

[BP]

GamerDude, all things being equal (size, gravity, atmo) 200 km would be a reasonable minimum orbit.

The wide range an orbit can take is why I don't figure the gravitic devices really have a gravity based limit based on 'can reach/upto orbit'.

For me - from a gaming standpoint - orbit is just a term relating to where one parks a station or ship (holding or scanning pattern). Stations would liklely be higher up (the 10,000 km might be reasonable for this - though geosync or a lagrange point might make more sense.

(Of course getting to orbital altitude isn't the same as being in orbit - and that leaves competeing with those things that are )

 

[RandyT0001]

Well for an airless world or one with just a trace atmosphere once you get to an altitude that is higher than the world's tallest peak you can orbit. Once there if you can reach the necessary orbital speed you can be in freefall or zero g.

 

[BP]

Well for an airless world or one with just a trace atmosphere once you get to an altitude that is higher than the world's tallest peak you can orbit. Once there if you can reach the necessary orbital speed you can be in freefall or zero g.

Lower than that if the peak is not in your path - or you are aiming for a short orbit

 

[captainjack23]

Well for an airless world or one with just a trace atmosphere once you get to an altitude that is higher than the world's tallest peak you can orbit. Once there if you can reach the necessary orbital speed you can be in freefall or zero g.

Lower than that if the peak is not in your path - or you are aiming for a short orbit

Technical term is Lithobraking........ :wink:

 

[BP]

Technical term is Lithobraking........ :wink:

:lol: Humbly impressed by your eloquence...