Stealth Jump Flare Detection

T

Terry Mixon

Emperor Mongoose
My players have a ship with the ability to stealth jump and are about to sneak into an area where they might be detected on emergence from jump space, so I looked at the rules. I'm a little confused.

The drive says: Stealth Jump: A stealth jump drive minimises the burst of radiation caused by the transition from jump space into real space. Normally, a ship that emerges into real space is automatically detected if it emerges within the minimum detail range of the sensor. However, detecting a ship equipped with a stealth drive emerging into real space requires a Formidable (14+) Electronics (sensors) check (1D rounds, INT or EDU) if it is within the ‘limited’ detail range of the sensors or automatically fails if outside the minimum detail range. Stealth jump requires two Advantages.

I'm assuming the detection is for visual sensors, though I didn't find anything to nail that down.

The grade of the sensor will add or subtract a DM:

Basic -4
Civilian Grade -2
Military Grade +0
Improved: +1
Advanced +2
Superior ?? (the ship spreadsheet has TL-16 sensors and the ship the players has is that tech level, but I can read all the text for this one. What would this DM be? +4? Not needed for the others to detect them, but I'm curious.

Looking at the sensor range chart:
Range Visual
Adjacent Full
Close Full
Short Limited
Medium Limited
Long Minimal
Very Long Minimal
Distant None

Those ranges are:

Adjacent 1km or less
Close 1–10km
Short 11–1,250km
Medium 1,251–10,000km
Long 10,001–25,000km
Very Long 25,001–50,000km
Distant More than 50,000km

So, that means it automatically fails at Distant range of 50,000+ km and is a Formidable check at inside the "limited" band 10,000 or less. What about the "minimal" band of 10,001-50,000km? It's not mentioned at all. Would it be an impossible check? Should it also be formidable? Something else? Seems like kind of a glaring (forgive the jump flash pun) omission.
 
There is a recent thread on this also:

Jump Detection Range

Does anyone know at what range a Jump Flash is no longer detectable? HG pg 26 says, "Far (over 5,000,000km): At these ranges, sensors can spot the signature of ships making jumps (inbound or out) and can determine only whether a contact is a ship or other similar-sized astronomical body. In...
forum.mongoosepublishing.com

One of the factors you did not include is the size of the ship. Going with Adventure Class sizes it seems that at 10-50km should be an Impossible check based on Stealth.
 
CRB '22 page 160
This gives you the sensor range and the detail they each have at each range band. The TL of the ship sensors tell you which kinds of sensor it has, as well its DM to doing sensor checks.
Civilian sensors have Visual (cause most sophonts have eyes), EM and Radar/Lidar.
Jump Flashes are EM emissions, we look to the EM sensors.
EM sensors Min. at Long Range.
So basically, the detecting ship would need to be at the 10d limit and it need to be pretty much where the stealth ship is entering the system at.
50k km for the area of a solar system, is sitting in someone lap. Remembber that ships can enter the system, at any point along the ecliptical that is toward their orgin system. The stealth ship, basically has hundred of million km of ecliptical to enter into.

The target number is 14.
If the detecting ship has Civilian Sensors, that imposes DM-2 to the roll.
So the roll would be
Electronics: Sensors Skill rank+EDU or INT DM -2 vs 14.
To have any chance of making the roll with a MoE of +0, they would need an overall DM+4, which is pretty high. They would need to roll a 12.

Now what gets vague is what happen when the sensor tech gets MoE over 0. The CRB gives us the general information they get with a success. For EM sensors, its Minimal is basically binary. Something is there or not.
So if the Sensor Tech got an MoE +0, they would just know, that a thing happen, 50k km over there. Not that it was a jumpflash. Just that, 'hey, there EM noise over there.'
At my table, the higher the MoE the more information they get. I also try to respect the career and skill rank they have. Which is an inference of experience and ability. So like MoE +2, (a roll of 16) they know it was a jumpflash. If they have like Skill Rank 2 or they were in the navy. They know it was a supressed flash. MoE +3-4, (roll of 17-18) the size of the jumpflash, which tells them the jump distnace or the volume of the ship.

For my table, I would not like a PC sensor crew member take their time to gain a DM+2 on their roll.
The reason why I would deny this, as for my table, I attempt to ask what the Standard operating procedure of of their job is. Do they usually just be really slow at reporting everything they see on their sensor roll. Probably not. So why would they do it now?
I dont really do that to stop bbad metagaming. Having the players declare what the character SoP just reduces redundant conversation and it allows the gm to more cleaning do surprises as you can NPC operate against the sop.
 
Anstett said:
There is a recent thread on this also:

Jump Detection Range

Does anyone know at what range a Jump Flash is no longer detectable? HG pg 26 says, "Far (over 5,000,000km): At these ranges, sensors can spot the signature of ships making jumps (inbound or out) and can determine only whether a contact is a ship or other similar-sized astronomical body. In...
forum.mongoosepublishing.com

One of the factors you did not include is the size of the ship. Going with Adventure Class sizes it seems that at 10-50km should be an Impossible check based on Stealth.
Click to expand...
I'm reading that one, too. Thanks.

It's hard pulling all the desperate parts of this together from multiple books. ;)

For jump flare detection, I'm not sure the size matters. Even so, I couldn't find how ship size affected the sensors. Do you have a book and page number I could go hunting it at? I was able to find info for initial detection and stealthed ships, but that's not jump flare either.
 
agentwigggles said:
CRB '22 page 160
This gives you the sensor range and the detail they each have at each range band. The TL of the ship sensors tell you which kinds of sensor it has, as well its DM to doing sensor checks.
Civilian sensors have Visual (cause most sophonts have eyes), EM and Radar/Lidar.
Jump Flashes are EM emissions, we look to the EM sensors.
EM sensors Min. at Long Range.
So basically, the detecting ship would need to be at the 10d limit and it need to be pretty much where the stealth ship is entering the system at.
50k km for the area of a solar system, is sitting in someone lap. Remembber that ships can enter the system, at any point along the ecliptical that is toward their orgin system. The stealth ship, basically has hundred of million km of ecliptical to enter into.

The target number is 14.
If the detecting ship has Civilian Sensors, that imposes DM-2 to the roll.
So the roll would be
Electronics: Sensors Skill rank+EDU or INT DM -2 vs 14.
To have any chance of making the roll with a MoE of +0, they would need an overall DM+4, which is pretty high. They would need to roll a 12.

Now what gets vague is what happen when the sensor tech gets MoE over 0. The CRB gives us the general information they get with a success. For EM sensors, its Minimal is basically binary. Something is there or not.
So if the Sensor Tech got an MoE +0, they would just know, that a thing happen, 50k km over there. Not that it was a jumpflash. Just that, 'hey, there EM noise over there.'
At my table, the higher the MoE the more information they get. I also try to respect the career and skill rank they have. Which is an inference of experience and ability. So like MoE +2, (a roll of 16) they know it was a jumpflash. If they have like Skill Rank 2 or they were in the navy. They know it was a supressed flash. MoE +3-4, (roll of 17-18) the size of the jumpflash, which tells them the jump distnace or the volume of the ship.

For my table, I would not like a PC sensor crew member take their time to gain a DM+2 on their roll.
The reason why I would deny this, as for my table, I attempt to ask what the Standard operating procedure of of their job is. Do they usually just be really slow at reporting everything they see on their sensor roll. Probably not. So why would they do it now?
I dont really do that to stop bbad metagaming. Having the players declare what the character SoP just reduces redundant conversation and it allows the gm to more cleaning do surprises as you can NPC operate against the sop.
Click to expand...
Thanks for the explanation. What about the limited detail range? Treat it like minimal? Harder? The rules seem to miss between 10,000 and 50,000.
 
agentwigggles said:
It’s a range band. Anything in the range band is Minimal.
Click to expand...
I said limited above and should have said minimal. The stealth detection rules mentioned a formidable check within limited detail and automatic failure outside minimum detail. That leaves minimal detail completely unresolved by my reading. I know this might sound nit picky but I just want to understand the rules. Sorry.

Let me rephrase that the rules seem to read in plain English. Below 10,001km, Formidible roll to detect a jump flare. 50,000+km auto fail to detect.

It leaves 10,001-50,000 with no method to treat it.
 
Last edited:
The stealth rules are extremely favorable for the ship trying to hide. Mongoose tends to put excessive difficulties on a lot of tasks and this is one of them, imho.
 
A stealth ship with the exepensive stealth ship compotents should be hard to detect.
In this conversation the example given was with a civilian ship, detecting a stealth ship at stupid ranges.
And yea, thats hard to do so.
 
The initial post was about stealth jump. That just makes the jump drive 25% more expensive. That's not nothing, but it isn't crazy expensive and only requires TL15 for Jump 4 or less.

Also, it is a 14+ to detect a stealth jump flash exit at Limited distance. Civilian sensors have -2 on top of that. Note that limited is, at best, Long Range. 25k kilometers.

Actually spotting a ship at minimal range is an 8+ before modifiers for quality of sensors. That kind of stealth is actually pretty difficult to be good at, in that it would be extremely expensive and require running on minimal power & no thrusters. But minimal sensors just tell you that an object is over there. You don't know much about what it is.

The important thing is that you can't spot the jump flash at that range in Mongoose 2e if it has the stealth jump improvement. And that's normally what alerts you that this is definitely a ship arriving without you having to get within shooting range for a detailed scan.

However, since thermal is one of the longest ranged sensors in MgT2e, this just spirals back to the heat sink discussion. Does painting your hull hide your heat from thermal sensors?
 
Terry Mixon said:
My players have a ship with the ability to stealth jump and are about to sneak into an area where they might be detected on emergence from jump space, so I looked
Superior ?? (the ship spreadsheet has TL-16 sensors and the ship the players has is that tech level, but I can read all the text for this one. What would this DM be? +4? Not needed for the others to detect them, but I'm curious.
Click to expand...
If that is my ship spreadsheet, go to the SSD page, bottom right corner.
 
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