Laser changes and the tactical use of missles

[BP]

A 6G ship going from Earth to Jupiter is hitting top speeds ~9160 km/s. Too fast to detect & do anything about it, other than collide. Either that hull can handle ~41,952,800,000 joules or, say bye, bye. Especially, the bridge crew hanging around the ships nose sitting behind glass. LOL

No, it is not - even at max RW distance, it is still only going ~3800 km/s max at midpoint turn-around (or its gonna hit Jupiter - though no less dramatic for the bridge crew to be sure).

The joules of kinetic energy should state the mass it is referring to. In this case it would be only ~7,220,000,000 joules for a single gram (ignoring relativistic effects and frame of reference issues, of course )

 

[BP]

...
Well in MgT there are collisions. Micrometeorites and space junk appear on the Space Encounters table, and under the Collision entry it does state that 'Almost any collision at high speed will destroy even the most powerful spacecraft.' So Gareth did take things into account up to a point, and decided to leave out in-depth scientific accuracy in favour of simple mechanics and keeping it fun.

Ah - since I use my own 'encounter' uhm.. 'logic' - missed that! Sounds very reasonable to me.

Just a note on all that massive kinetic energy and the 'obliterating of ships'... to the force per unit area and adding applied force (elasticity of the collision with structural and thermal energy dispersion, etc.) - that energy is only fully applied if the colliding object does not pass thru (or bounce off - though unlikely, even if wedge shaped for the velocities being referred to). Unless the object exposes a large contact area or very special deformative properties - it will 'simply' pass thru, only expending a portion of its kinetic energy on its victim... (though that could still be very bad - and, in certain extreme situations, even worse with more armour)

Just as has happened for RW space probes on most occasions.

...
After all, how many deep space robotic missions have we sent across our solar system which have exploded dramatically from a micro-meteorite encounter? And there must have been several centuries worth of flight time logged between them.

Actually, at least one has - but that was trailing a comet! (Not counting impactors there - one actually was lost from impacts at around the expected time and sized particles.)

Cool! I'll have to track details of that one down.

Sorry - I usually provide links, but for the life of me can't remember which comet probe this was.

There have been so many comet ones in recent years, I've lost track of many of them. Pretty sure it wasn't related to follow on for Deep Impact (dad worked on that one) or a NASA probe, but remember a paper detailing the pre-flight analysis and accuracy to actual results...

 

[rust]

I suspect the space probe mentioned by BP could have been ESA's
Giotto mission:
http://en.wikipedia.org/wiki/Giotto_mission

While is was not completely destroyed, it was very badly damaged,
and for a short while even considered destroyed. It had lost several
of its scientific instruments because of the impacts, and so the later
stage of the mission was not exactly a success.

 

[BP]

Could have been Giotto - but that was quite some time back (and it wasn't lost - though it could be just my mind that is lost )

Actually, jogging the memory, there is at least one failed NASA mission that might have been attributed to a hit by space debris shortly after orbiting (some of the tech ended up in New Horizons) - but more likely it was a thermal problem.

 

[BP]

Ah - found it - CONTOUR.

Also found the ASAP report, but since it has an ITAR notice, I won't post a link - but here is the relevant part of the executive summary findings:

• The Board was unable to determine with certainty the proximate cause of the failure due to the lack of data during the solid rocket motor burn phase of the mission. The Board was able to narrow an initial extensive list of possible causes to a few possible proximate causes. ...
  Probable Proximate Cause
  • Overheating of the CONTOUR spacecraft by the solid rocket motor exhaust plume
  Alternate Proximate Causes
  • Catastrophic failure of the solid rocket motor
  • Collision with space debris or meteoroids
  • Loss of dynamic control of the spacecraft
  

 

[Mongoose Pete]

As a matter of interest, any idea how fast micrometeorite mass per cubic kilometre drops off above the invariable plane? If the amount of debris thins out significantly, then ships may be able to travel somewhat faster if they take an arcing trajectory across a system.

Just a thought.

 

[BP]

As a matter of interest, any idea how fast micrometeorite mass per cubic kilometre drops off above the invariable plane? If the amount of debris thins out significantly, then ships may be able to travel somewhat faster if they take an arcing trajectory across a system.

Just a thought.

A few computer models have been made, but they rely on very limited data. (see here for some possible related info...)

Past Saturn, the last computer models I recall estimated 50 tons per day of matter from colliding objects in Kuiper belt (possibly useful in identifying planet bearing systems) mostly situated within a fair arc of the system plane. In the inner system, most of the interstellar dust is concentrated around the asteroid belt, IIRC. Not sure how far the main belt extends above/below plane - I am sure that one would want to avoid paths that took one to near the natural trojan points based on system gas giants.

New Horizons does have an instrument aboard for investigating dust data on its path to Pluto. Here is a link to some data

[Reminds me, dad promised a PDF of the to scale solar poster for New Horizons he has 'hanging' in his 'lab' - its, uhm, quite long - and very probably the basis for the image linked above.]

But, yes, in general, the densest region is spinning in a 'disk' shaped cloud centered on the Sun. However, a sufficient arcing trajectory to get clear of that cloud could markedly increase the distance traveled - so higher 'speeds' may be no more advantageous in that situation (i.e. trip may take as long/longer). Not to mention greater distance from possible help and normal system baseline sensor data.

(P.S. - Ulysses data may provide some answers, at least as to count density and median object sizes...)

 

[Mongoose Pete]

New Horizons does have an instrument aboard for investigating dust data on its path to Pluto. Here is a link to some data

What are the units for Geography, Number of Hits, Hit Mass and Density on the longview chart?

Also are the dead stretches underlined in red actually clear regions, or was the instrument turned off for those periods?

But, yes, in general, the densest region is spinning in a 'disk' shaped cloud centered on the Sun. However, a sufficient arcing trajectory to get clear of that cloud could markedly increase the distance traveled - so higher 'speeds' may be no more advantageous in that situation (i.e. trip may take as long/longer). Not to mention greater distance from possible help and normal system baseline sensor data.

Considering safe in-system top speeds for 'unarmoured' MgT ships might be around 100km/s(*), which is perfectly adequate for 100d transits (about the same journey time as a 3g ship doing a classic midpoint turnover transit at an earth sized planet - unless my maths have let me down again); being able to freely accelerate up to several thousand km/s (or higher) should significantly reduce transit time even if the overall distance was doubled.

On the other hand, capping in-system velocity for safety would make cross system jumps economically more viable. :wink:

Actually the more I think about 'safe' velocity limits the more I like the idea. Need to escape from the pirate stern chasing you? Play chicken and accelerate up to speeds where you start gambling the ship's safety, rolling collision chances each hour... although that might be a little boring unless both protagonists are in M6 ships.

Or you could apply the same idea to any cross-system race scenario. Time critical rescues, evacuating a ship with a countdown bomb aboard (when the criminals have stolen the ship's boat and vacc suits), racing to claim a valuable asteroid before the rival megacorp, actual competitive races, and so on.

(*) its a slightly abstract figure, but technically plausible considering the extrapolated hull strengths from MT and near future sensor capability. As armour thickens and sensor resolution improves, 'safe' velocities should increase commensurately.

 

[BP]

Limiting speeds is certainly more 'realistic', regardless of other trade-offs, but as a game, quite unappealing...

In MgT terms this would mean increasing operational fuel for months in order to refuel at, say, most gas giants - or making in-system jumps and using 10% dtons fuel and a full week in non-interacting time (i.e. - 'traveling' and having the opportunity for collisions, pirates, artifacts, etc.)

Personally, if the concept is bothersome, rather just go with 'shields' - especially if already basing things on gravitics and constant acceleration regardless of actual gravity fields... its a very minor handwave to add to accommodate a virtual reality.

Plus, irregardless of the ship's speed - the speed of the incoming objects can be anything. So, there is still a need for 'shields' if one accounts for such.

 

[Mongoose Pete]

(P.S. - Ulysses data may provide some answers, at least as to count density and median object sizes...)

Okay, I downloaded the Ulysses DUST instrument data and shoved it into a spread sheet. It looks like the median impact velocity of particles was 28km/s. The average particle size however was much lower than I'd expected, only 8.15e-10 grams. The largest impact recorded in the was only 9.47e-7 grams over the course of the mission.

However, I am unsure if this value is simply constrained by the sensitivity range of the instrument, or if there simply aren't that many micrometeorites of large scale above the equatorial plane. :?

 

[BP]

...
What are the units for Geography, Number of Hits, Hit Mass and Density on the longview chart?

Not sure - image came from a bookmark I had - try here http://lasp.colorado.edu/sdc/ - looks like a University payload that was placed on NH (my dad built one of the other instruments - but don't recall if he did any actual instrument install since that probe was final tested and assembled by NASA/John Hopkins (APL), IIRC).

Suspect there might be coast/calibration dead zones - sure the data was only transmitted in spurts (so may also be memory limits). Most probes do not transmit scientific data continuously due to power requirements.

Not sure the tech used - but this was a 'dust' detector - so nothing to worry about in MgT terms, just an interesting view at possible dispersion patterns.

 

[BP]

...
However, I am unsure if this value is simply constrained by the sensitivity range of the instrument, or if there simply aren't that many micrometeorites of large scale above the equatorial plane. :?

Not sure the mission parameters - seem to recall the actual objective was to only look at small 'dust' particles (one of its strengths).

Was really referring to that more for dispersion patterns rather than your mass question - don't really think there is anywhere near enough data to answer that question. Just computer models that are mostly about planetary formation.

The Oort cloud, system disk and Belt mass have a wide range of estimates - modern computer models tend to lower masses (like 3~4 Earths in Oort cloud, while others have 1000+). Even the closer asteroid belt masses range quite widely (1/1000 Earths to 2 Earths IIRC) - and, of course, the asteroids get perturbed a lot (hence the near Earth ones like those last Wed that passed between the Earth Moon system).

 

[Mongoose Pete]

Limiting speeds is certainly more 'realistic', regardless of other trade-offs, but as a game, quite unappealing...

Actually its having the opposite effect for me, opening up all sorts of ideas and explanations of how things work.

For example it actually aids piracy, or at least piracy on remote research bases, mining ships or vessels refuelling at mid-system gas giants. A pirate can jump in to the proximity, cruise for a couple of days to catch an opportunistic target (or directly hit a preplanned objective) and jump out again with near impunity, since local defence forces will no longer be able to scramble across system at flat out 6g acceleration.

Military-wise it changes the tactical deployment of vessels, since outlying pickets will be on their own for a while till reinforcements can come to support them. This opens possibilities for PC level military conflicts at a smaller scale without having to worry about the rest of the home/enemy fleet engaging.

It also hammers the last nail in the coffin of c-fractional ships being used as planet killers (a trope I've always disliked), since there's no way you can accelerate a vessel up to those speeds without it being ripped apart by dust.

In MgT terms this would mean increasing operational fuel for months in order to refuel at, say, most gas giants - or making in-system jumps and using 10% dtons fuel and a full week in non-interacting time

Actually, using our own solar system as an example, if Earth was on the other side of the sun to Jupiter, then a typical PC owned 1g or 2g ship will spend near enough the same amount of time to get to our 'nearest' gas giant as jumping there direct anyway.

Personally, I've rarely experienced Traveller adventures where things happen to the ship en-route to places - save for the occasional murder mystery or passenger hijack attempt, which tend to happen aboard the vessel itself. Most adventures in my experience occur when you finally reach the final adventure destination. Even micrometeorite events are usually scripted.

However since as you pointed out, micrometeorites have their own velocity, dangerous collisions can still occur even during plodding transitions to and from jump. :wink:

Ah well, its been a interesting thread. Thanks for the data BP, its been very useful. You're a scholar and a gentleman!

 

[BP]

...Actually its having the opposite effect for me, opening up all sorts of ideas and explanations of how things work.

Good to hear... as a fan of Jeff Goldblum's "Must go Faster!" approach, and a background in non-destructive testing, I like shields

In MgT terms this would mean increasing operational fuel for months in order to refuel at, say, most gas giants - or making in-system jumps and using 10% dtons fuel and a full week in non-interacting time

Actually, using our own solar system as an example, if Earth was on the other side of the sun to Jupiter, then a typical PC owned 1g or 2g ship will spend near enough the same amount of time to get to our 'nearest' gas giant as jumping there direct anyway.

Ah - I was referring to the 100 km/s speed limit - that would take over 110 days (at 86,400 x 100 km/day)! At 1G one would still be pushing 3000 km/s... as I believe Jupiter is 968 million km at its nominal farthest distance from us (had recently looked that up after checking out an instrument being fabbed for JUNO mission - it gave me a strange feeling looking at something that will actually be going to Jupiter...)

...Personally, I've rarely experienced Traveller adventures where things happen to the ship en-route to places - save for the occasional murder mystery or passenger hijack attempt, which tend to happen aboard the vessel itself. Most adventures in my experience occur when you finally reach the final adventure destination. Even micrometeorite events are usually scripted.

Being an isolated CT ref, I took the name 'Traveller' quite literally - probably 1/3 of my adventures where 'in transit'. Nearer transition phase (midpoint) everything was planned rendezvous (matched speeds) and unexpected impacts with pirates rarely factored in - those were more for destinations/refueling, excepting one or two phony emergency beacon adventures...

...However since as you pointed out, micrometeorites have their own velocity, dangerous collisions can still occur even during plodding transitions to and from jump. :wink:

Yeah, comets can reach 'speeds' in excess of 300 km/s (near the Sun - and recall models predicting half again more than that) - not sure what 'speeds' are common in areas that would normally be traversed, but our Sun is also not one of the larger specimens in the universe. So I've always assumed smaller objects could at least reach those 'speeds'. I suspect faster 'speeds' would only be achieved by extrasolar particles just 'passing thru' or recently captured by our sun.

...Ah well, its been a interesting thread. Thanks for the data BP, its been very useful. You're a scholar and a gentleman!

Aw - shucks - you're too kind. (And, I'm not so sure about that latter stuff - but I am kind to small animals!).

Quite enjoyed it. You obviously take your research seriously and present things well - looking forward to picking up Darrians, even though I don't do much in the 3I!

 

[apoc527]

A re-release of Traveller at a FF&S level would not have come anywhere close to being as successful.

As they say on the Internets, "QFT." This is the truest statement I have read recently. If MGT had even remotely resembled any edition of FF&S, I'd never have touched it with a ten foot pole. As it is, I've purchased almost every supplement and plan to continue to do so (and my group has bought a couple of Core Books as well).

 

[SSWarlock]

...If MGT had even remotely resembled any edition of FF&S, I'd never have touched it with a ten foot pole. As it is, I've purchased almost every supplement and plan to continue to do so (and my group has bought a couple of Core Books as well).

Same here..and I liked FF&S.

By the by, could a handwave reason for not having a bunch of in-game collisions with space junk be ships normally leave/enter a system above and below the ecliptic? Perhaps I should've started a different discussion thread but what the heck.

 

[Egil Skallagrimsson]

Ok, I give up, what is FF & S?

Egil

 

[rust]

Ok, I give up, what is FF & S?

Fire, Fusion & Steel, the technology design system introduced by Traveller
New Era, with about the same complexity as GURPS Vehicles - nice for the
occasional vehicle design, but a headache to use more often.

 

[Egil Skallagrimsson]

Thanks, sounds like something I had best avoid.

Though I quite like designing space ships with MGT rules, one run through "Military Vehicles" was enough for me, tend to use the vehicles suggested in core book, military vehicles and civialian vehicles as a base, and fiddling any extras needed.

Egil