T4 Only: Some people say no stealth in space, a discussion.

[Dragoner]

a method of active cooling and heat control, and not a method of stealth

?

(not really seeing a point here)

 

[whulorigan]

?

I think we are obviously talking past each other.

Your original comment was in reference to Condottiere's tongue-in-cheek comment:

I miss squatting in the swamp, when I overheat.

I wonder if you can skim a gas giant, and dump some of that.

use laser cooling https://en.wikipedia.org/wiki/Laser_cooling

Please expand on your thoughts relative to the original comment.

 

[Badenov]

I think the point was cooling = stealth to IR detectors?

 

[Dragoner]

If people want to lean into the fiction that is fine, others use the game to explore science ideas

 

[whulorigan]

I think the point was cooling = stealth to IR detectors?

And that is what I was presuming. In which case I do not understand what is failing to connect for someone who wants to make the "science connection". This is basic thermodynamics.

The ship has onboard heat well in excess of background, which it is radiating. If you want to cool it, you need to move that heat somewhere else. To do that you need a mechanism that moves the heat, which does so by performing work. Performing work produces heat, which means you are now generating heat to move the initial heat. So now you have more heat than you started with. This is fine if your goal is merely to quickly-cool a system and vent/radiate that heat away. But if you want to mask thermal emissions (i.e. heat), it has to go somewhere else, and so does the heat generated by the system making it need to go somewhere else.

If you are using the laser system to do it, your mechanism is the laser, which generates heat during its operation. That heat from the laser will either be vented/radiated internal to the ship as additional heat to dispose of, or external to the ship as additional radiated heat. How is this aiding masking/stealth?

 

[whulorigan]

If people want to lean into the fiction that is fine, others use the game to explore science ideas

Which I am fine with on either side. But what you are suggesting can't be done as a method for masking/stealth, per Thermodynamics, presuming you want to explore science ideas.

 

[Dragoner]

Don't mix the processes (I can see you are not understanding how the laser is working, it isn't transfering heat with a material)

 

[whulorigan]

Don't mix the processes

?!?

You don't have a choice. You have heat to move. And you are generating more heat doing it. You started with Heat H₁ on the ship. Now you have Heat H₁ (which you have removed, and it has to be accounted for - it has gone somewhere) + H₂ generated by your heat-removal system and is radiating from the system either into the interior of the ship or into space exterior to the ship.

Can you elaborate a bit more on your system as you envision it?

 

[mike wightman]

Change the state, and then redirect it, what cooling systems do.

Only with a means of removing the heat from the closed system.

Consider your fridge, how does it keep cool? It moves the heat to the back of the fridge where it is removed via convection and radiation, ie external air circulating.
Your fridge is not a closed system, electricity goes in to do work, that work generates waste heat, the waste heat is removed to the room external to the fridge.

You can only remove heat from a spaceship by:
heating something up then chucking that hot something off your ship
or
radiating it as EM.

 

[Dragoner]

The science you are not trying to force on anyone doesn't work the way you think it does.

Please, never post to me ever again. Bitter attacks and insults is all I have recieved for at least trying to look at things from a scientific angle. This is why it is not worth even trying.

 

[whulorigan]

Don't mix the processes (I can see you are not understanding how the laser is working, it isn't transfering heat with a material)

It is removing momentum (i.e. "Heat") from the molecules by actively countering with the opposite-sign momentum of the photons in a colision reaction, effectively. To reduce the Heat (i.e. molecular momentum) by a given amount, you must transfer an equal magnitude but oppositely directed momentum of photons to cool the molecules by the said amount. Since momentum (p=mv=hf/c), a vector quantity, is directly related to energy (E = ½mv² = hf), a scalar quantity, that means the photon energy must equal the molecular energy (i.e. heat) to be cooled. That further means that the laser system must be able to generate the power to produce a laser pulse sufficient to produce that level of energy. And since no system is 100% efficient, it means that at the very least, even with an incredibly efficient laser system, you will use more energy than the output beam you are creating, and generate heat as well as a byproduct of operation due to system losses. The photons themselves will either scatter in the process of cooling (and effectively be waste heat, picking up the energy of motion of the molecules), or they will be absorbed by the molecules as they slow down in reaction to the interaction with the opposed laser photons (and give up their energy of motion by re-emitting the photons as radiant heat at a different wavelength, the molecules thus becoming cooled - and the radiant heat effectively becoming waste heat).

So the laser mechanism is generating heat of operation; and the laser photon interaction with the molecules is carrying the heat of motion of the molecules away by reradiating at a different wavelength, thus cooling the molecules.

What does this have anything to do with convective heat transfer?

And you still have the heat radiation problem that I have been talking about, that has not been addressed.

 

[mike wightman]

Please, never post to me ever again. Bitter attacks and insults is all I have recieved for at least trying to look at things from a scientific angle. This is why it is not worth even trying.

I have deleted several replies as per your request - but I will respond this one last time. It is all well and good exploring a scientific angle, but when it has been repeatedly pointed out that the science you are describing doesn't work the way you want it to you make a personal attack on my understanding of thermodynamics.

I will now comply with your request to have no further interactions with you.

 

[Dragoner]

It is removing momentum (i.e. "Heat") from the molecules by actively countering with the opposite-sign momentum of the photons in a colision reaction, effectively. To reduce the Heat (i.e. molecular momentum) by a given amount, you must transfer an equal magnitude but oppositely directed momentum of photons to cool the molecules by the said amount. Since momentum (p=mv=hf/c), a vector quantity, is directly related to energy (E = ½mv² = hf), a scalar quantity, that means the photon energy must equal the molecular energy (i.e. heat) to be cooled. That further means that the laser system must be able to generate the power to produce a laser pulse sufficient to produce that level of energy. And since no system is 100% efficient, it means that at the very least, even with an incredibly efficient laser system, you will use more energy than the output beam you are creating, and generate heat as well as a byproduct of operation due to system losses. The photons themselves will either scatter in the process of cooling (and effectively be waste heat, picking up the energy of motion of the molecules), or they will be absorbed by the molecules as they slow down in reaction to the interaction with the opposed laser photons (and give up their energy of motion by re-emitting the photons as radiant heat at a different wavelength, the molecules thus becoming cooled - and the radiant heat effectively becoming waste heat).

So the laser mechanism is generating heat of operation; and the laser photon interaction with the molecules is carrying the heat of motion of the molecules away by reradiating at a different wavelength, thus cooling the molecules.

What does this have anything to do with convective heat transfer?

I know all this, though I am not seeing any point in having the discussion anymore

 

[whulorigan]

Please, never post to me ever again. Bitter attacks and insults is all I have recieved for at least trying to look at things from a scientific angle. This is why it is not worth even trying.

Nobody is trying to post bitter attacks. And nobody has insulted you up to this point that I have seen. What people have done is try to show you that you have a misunderstanding about Thermodynamics and how it works. And despite trying to lay it out simply and engage with you on the subject, you simply continually tell me that I (and others) don't understand science because I simply do not dutifully concede your point and move on.

I would like to have the conversation, but if you are not going to actually listen to what others are trying to say, and just suggest that nobody else understands anything as you do, there isn't really much point in trying to discuss it further.

If you would like to discuss the issue, then can you please give a slightly longer and more in-depth description of what you are thinking than simple one-liners and links to wikipedia articles that have information that while they are certainly informative and have value to the community, do not in fact directly answer the question asked. (Or at the very least, note a paragraph or sub-paragraph or section-header that you believe addresses the question at hand).

I am well aware of how the Laws of Thermodynamics work, as well as the general scientific concept (though perhaps not the minute details) of laser cooling.

 

[Spinward Flow]

Doesn't work to remove waste heat from a closed system.

Where does the waste heat generated by operating the cooling laser go?

At the risk of being insulting by pointing out the "megawatt obvious" answer ... laser cooling (as a concept) would work to remove waste heat by "opening" the otherwise "closed" system in order to dump the excess heat "overboard" out into space using the laser beam.

Instead of being a "passive" radiator system (big metal fins rejecting IR photons in all directions) ... instead you "heat pump" concentrate the waste heat factor in such a way as to use a high power laser beam to reject the excess heat "overboard" out into space in a coherent direction (because, laser).

David Brin made this concept the centerpiece of the Sundiver spacecraft prominently featured in the first of his Uplift series of books (which are mildly famous).

If the spacecraft/starship is not a "closed" system ... but rather an "open" one (in terms of waste heat rejection) then laser cooling ought to work just fine (conceptually). The actual engineering might get ... interesting ... but the same is true for maneuver drives and jump drives, so choose carefully which (mole)hill you want to die on with regards to this point.

And to be clear, you aren't pointing the (cooling) laser AT your ship. Instead you're using concentrated to extremely high temperatures (waste) heat (via refrigeration heat pump principles) such that the laser beam getting dumped "overboard" carries the heat away from the craft inside the laser beam itself (as high energy photons shot outside).

You would have more heat in the end than you started with. Laws of Thermodynamics.

If you hold the binoculars backwards when you look through them, they do not magnify what you're looking at.

What I mean by that is if you "do it wrong" from the get go, because you're applying what you think you know incorrectly, then you're (obviously) going to reach the wrong conclusion with confidence.

The proof of what I'm saying here is SO MUCH EASIER to prove (and explain) by just transcribing the relevant passage out of the book Sundiver by David Brin.

(My paperback copy) Sundiver by David Brin © 1980, p141-142, chapter 14, The Deepest Ocean:

old grandfather NASA decided that it would be interesting to drop expendible probes into the Sun to see what happened.

They discovered that the probes did a quaint thing when they got close. They burned up.

In America's "Indian Summer" nothing was thought impossible. Americans were building cities in space--a more durable probe couldn't be much of a challenge!

Shells were made, with materials that could take unheard of stress and whose surfaces reflected almost anything. Magnetic fields guided the diffuse but tremendously hot plasmas of corona and chromosphere around and away from those hulls. Powerful communications lasers pierced the solar atmosphere with two-way streams of commands and data.

Still the robot ships burned. However good the mirror and insulation, however evenly the superconductors distributed heat, the laws of thermodynamics still held, Heat will pass from a higher temperature to a zone where the temperature is lower, sooner or later.

The solar physicists might have gone on resignedly burning up probes in exchange for fleeting bursts of information had Tina Merchant not offered another way.

"Why don't you refrigerate?" she asked."You have all the power you want. You can run refrigerators to push the heat from one part of the probe to another."

Her colleagues answered that, with superconductors equalizing heat throughout was no problem.

"Who said anything about equalizing?" the Belle of Cambridge replied. "You should take all excess heat from the part of the ship where instruments are and pump it into another part of the ship where the instruments aren't."

"And that part will burn up!" one colleague said.

"Yes, but we can make a chain of these 'heat dumps.'" said another engineer, slightly more bright. "And then we can drop them off, one by one..."

"No, you don't understand." The triple Nobel Laureate strode to the chalkboard and drew a circle, then another circle within.

"Here!" She pointed to the inner circle. "You pump your heat into here until it is, for a short time, hotter than the ambient plasma outside of the ship. Then, before it can do harm there. you dump it out into the chromosphere."

"And how," asked a renowned physicist, "do you expect to do that?"

Tina Merchant smiled as if she could almost see the Astronautics Prize held out to her, "Why I'm surprised at all of you!" she said. "You have onboard a communications laser with a brightness temperature of millions of degrees! Use it!"

Enter the age of the Solar Bathysphere. Floating in part by buoyancy and also by balancing atop the thrust of their refrigerator lasers, probes lingered for days, weeks, monitoring the subtle variations at the Sun, that wrought weather on Earth.

That era came to an end with Contact. But soon a new type of Sunship was born.

You would have more heat in the end than you started with. Laws of Thermodynamics.

I'm surprised that so few people on these forums are familiar with the COP (coefficient of performance) that can be achieved in heat pumps ... TODAY ... @ TL=7-8. Most heat pumps operate in the COP 3-5 range.

If I have a gas fired heater, the COP is always going to be less than 1.
If I burn a fuel + oxidizer that have a combined 100kJ of heat bound up in them, the "useful work" I'm going to be getting out of the gas fired heater is always going to be less than 100kJ of heat transfer.

However, with a heat pump that has a COP of (let's say) 4 rating ...
If I spend 25kw of electricity in operating the heat pump, with a COP 4 rating the heat pump will move 100kw of heat energy (hot to cold).
In other words, the heat pump "moves" more heat energy than the amount of energy you put into the system to move that amount of heat.

The cooling lasers can not remove heat from a ship without dumping even more waste heat from the operation of the laser into the ship.

"So certain are you. Always with you it CANNOT BE DONE. Hear you nothing that I say? You must UNLEARN what you have LEARNED."
- A certain Jedi Master to a disbelieving student

The heat from a refrigerator is radiated from the back of the fridge, and even then it is not a closed system as there is air to provide convective heat transfer and electricity id providing a constant energy input.

Oh man ... you are SO CLOSE to getting what you've been missing!

Here, let me help you.
We're going to do a MadLibs to make this REALLY OBVIOUS.

The heat from a refrigerator is radiated from the back of the fridge, and even then it is not a closed system as there is air to provide convective heat transfer and electricity is providing a constant energy input.

To make this a refrigerator laser on a spacecraft, we modify the following words:

The heat from a refrigerator is radiated from the back of the maneuver drive, and even then it is not a closed system as there is a refrigeration laser beam pointed overboard to provide high intensity radiative heat transfer (into the vacuum of space outside the craft) and electricity is providing a constant energy input.

Does that help?

 

[Spinward Flow]

No cooling systems ever work at all? (they do)

Of course they do. They do so by moving the heat of the system (H1) they are cooling from one place, to another place outside the system, and the cooling system itself generates heat (H2) in the operation, and vents it to the same place outside the system. So the heat from the system cooled is lowered by H1, and the region outside the system is heated by (H1 + H2).

If you have your cooling laser/system inside the ship, then you cool the interior by H1, and vent H1 + H2 back into the interior, or vent H1 + H2 to the exterior, which is more than the H1 which would be radiated by natural blackbody radiation alone (i.e. it cools faster via the mechanism, but with a greater external thermal signature because there is now more heat to move).

Right.
You vent H1+H2 to the exterior via high intensity laser radiation sending high energy photons out into space.
And if you dial the cooling laser radiation temperature up into the 100,000 Kelvins range and use a 1,000,000+ Kelvins heat source/battery to pump the laser with (such as a fusion reaction, perhaps? ) then you can reject the high energy ~100,000 Kelvins temperature photons out into the vacuum of space, cooling the entire system of the spacecraft/starship.

Yes, laser cooing is a very interesting process. But the thread is about stealth in space and/or masking and the issue raised was about how to reduce emissions from a vessel using components/subsystems within your vessel.

The trick with laser cooling of a spacecraft is that it allows you to collect/collimate/point the radiation cooling function into limited directions ... kind of like how a searchlight or a laser doesn't shine "as brightly" in all directions.
If you had a 10m radius sphere (20m diameter), the area of the sphere would be 4πr² ... or 1256.63706144m².
If your sphere was emitting 100 watts of heat energy per m², that sphere would be emitting 1,256,637 watts of heat energy (total).

However, if you "confined" the emission to only a single 1m² and dumped the entire 1,256,637 watts of heat energy through that single 1m², there would be no change in the total amount of heat energy being rejected out of the 10m radius sphere.

The "beam" option would be more ... intense and concentrated ... in the direction the beam is pointed at, than the "radiate in all directions" option, but the amount of "heat energy flux" being rejected to the outside would remain the same.

The engineering to DO that would be a little different ... but in terms of physics, the two methods are equivalent.

If you want to cool it, you need to move that heat somewhere else. To do that you need a mechanism that moves the heat, which does so by performing work. Performing work produces heat, which means you are now generating heat to move the initial heat. So now you have more heat than you started with.

Yes ... but ... as demonstrated with real world heat pumps TODAY, it is possible to "move" more heat than the amount of energy needed to do the "work" of moving that heat.

If I only need 25kw of electricity to move 100kw of heat, that's a COP (Coefficient of Performance) of 4.
The reason why this doesn't break thermodynamics is because there's a total of 125kw of energy involved to move 100kw of heat energy, but if "scaled right" a simple heat pump can "move more heat" than the amount of "work" being used to move that heat.

In the case of a spacecraft/starship, the waste heat needs to be rejected into the environment (space) ... and you usually can't use conduction/convection (in the normal sense) to do that ... which leaves radiation (see: EM spectrum) and, with sufficient technology, gravitic effects to "reject" waste energy into the external environment (space) around the craft.

Dial up the radiation temperature (photon energies) high enough and you can "squeeze" the waste heat rejection from going in ALL directions to only going in SOME directions (presumably aft of the maneuver drive). You can therefore "trade" the waste heat signature from being the same in all directions to being low in some directions at the expense of it being higher in other directions (see: aft of maneuver drive as an example).

This isn't all that much different from the notion of stealth in aircraft design, where they have different radar return cross-sections depending on the aspect relative to the radar emitter/sensor setup. Frontal stealth can be high, while side/aft stealth might be lower (for example).

 

[Ekofisk]

Caveat: I am NOT taking a position here; merely providing a link to information that illuminates (pun intended) one argument expressed so far:
Brin's Sundiver. (the interesting bits start around post #7).

 

[mike wightman]

At the risk of being insulting by pointing out the "megawatt obvious" answer ... laser cooling (as a concept) would work to remove waste heat by "opening" the otherwise "closed" system in order to dump the excess heat "overboard" out into space using the laser beam.

And the laser beam is easily detected.
next easily refuted point...

Instead of being a "passive" radiator system (big metal fins rejecting IR photons in all directions) ... instead you "heat pump" concentrate the waste heat factor in such a way as to use a high power laser beam to reject the excess heat "overboard" out into space in a coherent direction (because, laser).

Which interacts with the dust in space and re-radiates in all direction, easily detected
next...

David Brin made this concept the centerpiece of the Sundiver spacecraft prominently featured in the first of his Uplift series of books (which are mildly famous).

Yes and it was refuted pages and pages ago, it won't work
next...

If the spacecraft/starship is not a "closed" system ... but rather an "open" one (in terms of waste heat rejection) then laser cooling ought to work just fine (conceptually). The actual engineering might get ... interesting ... but the same is true for maneuver drives and jump drives, so choose carefully which (mole)hill you want to die on with regards to this point.

But it is closed so your point is baseless,
next...

And to be clear, you aren't pointing the (cooling) laser AT your ship. Instead you're using concentrated to extremely high temperatures (waste) heat (via refrigeration heat pump principles) such that the laser beam getting dumped "overboard" carries the heat away from the craft inside the laser beam itself (as high energy photons shot outside).

Which are easily detectable

If you hold the binoculars backwards when you look through them, they do not magnify what you're looking at.

no shit sherlock

What I mean by that is if you "do it wrong" from the get go, because you're applying what you think you know incorrectly, then you're (obviously) going to reach the wrong conclusion with confidence.

I am applying what is known, with confidence, because I am secure in my knowledge of the subject at hand

The proof of what I'm saying here is SO MUCH EASIER to prove (and explain) by just transcribing the relevant passage out of the book Sundiver by David Brin.

Pure handwavium of the first order, anyone with a moderate understanding of thermodynamics can poke holes in it, not to mention handwavium superconductors

I'm surprised that so few people on these forums are familiar with the COP (coefficient of performance) that can be achieved in heat pumps ... TODAY ... @ TL=7-8. Most heat pumps operate in the COP 3-5 range.

heat pumps are no different to fridges and air conditioners, they are not closed systems.

If I have a gas fired heater, the COP is always going to be less than 1.
If I burn a fuel + oxidizer that have a combined 100kJ of heat bound up in them, the "useful work" I'm going to be getting out of the gas fired heater is always going to be less than 100kJ of heat transfer.

In an open system, not a close one

However, with a heat pump that has a COP of (let's say) 4 rating ...
If I spend 25kw of electricity in operating the heat pump, with a COP 4 rating the heat pump will move 100kw of heat energy (hot to cold).
In other words, the heat pump "moves" more heat energy than the amount of energy you put into the system to move that amount of heat.

"So certain are you. Always with you it CANNOT BE DONE. Hear you nothing that I say? You must UNLEARN what you have LEARNED."
- A certain Jedi Master to a disbelieving student

Oh man ... you are SO CLOSE to getting what you've been missing!

Nope, you still don't get closed versus open.

Here, let me help you.
We're going to do a MadLibs to make this REALLY OBVIOUS.

The heat from a refrigerator is radiated from the back of the fridge, and even then it is not a closed system as there is air to provide convective heat transfer and electricity is providing a constant energy input.

To make this a refrigerator laser on a spacecraft, we modify the following words:

The heat from a refrigerator is radiated from the back of the maneuver drive, and even then it is not a closed system as there is a refrigeration laser beam pointed overboard to provide high intensity radiative heat transfer (into the vacuum of space outside the craft) and electricity is providing a constant energy input.

Does that help?

And can easily be detected.
This is too easy to refute.

 

[mike wightman]

Right.
You vent H1+H2 to the exterior via high intensity laser radiation sending high energy photons out into space.

Which are easily detected.

And if you dial the cooling laser radiation temperature up into the 100,000 Kelvins range and use a 1,000,000+ Kelvins heat source/battery to pump the laser with (such as a fusion reaction, perhaps? ) then you can reject the high energy ~100,000 Kelvins temperature photons out into the vacuum of space, cooling the entire system of the spacecraft/starship.

And can easily be detected once the laser exits your craft, the photons can be detected (they difract and spread, they interact with atoms and molecules in space which then re-radiate in every direction)

The trick with laser cooling of a spacecraft is that it allows you to collect/collimate/point the radiation cooling function into limited directions ... kind of like how a searchlight or a laser doesn't shine "as brightly" in all directions.
If you had a 10m radius sphere (20m diameter), the area of the sphere would be 4πr² ... or 1256.63706144m².
If your sphere was emitting 100 watts of heat energy per m², that sphere would be emitting 1,256,637 watts of heat energy (total).

And is easily detectable

However, if you "confined" the emission to only a single 1m² and dumped the entire 1,256,637 watts of heat energy through that single 1m², there would be no change in the total amount of heat energy being rejected out of the 10m radius sphere.

The "beam" option would be more ... intense and concentrated ... in the direction the beam is pointed at, than the "radiate in all directions" option, but the amount of "heat energy flux" being rejected to the outside would remain the same.

The engineering to DO that would be a little different ... but in terms of physics, the two methods are equivalent.

And is still easily detectable

Yes ... but ... as demonstrated with real world heat pumps TODAY, it is possible to "move" more heat than the amount of energy needed to do the "work" of moving that heat.

No it isn't or you have a perpetual motion machine.
You are just extending the volume of your system to include the outside world the heat pump is interacting with, it is an open rather than a closed system.

If I only need 25kw of electricity to move 100kw of heat, that's a COP (Coefficient of Performance) of 4.
The reason why this doesn't break thermodynamics is because there's a total of 125kw of energy involved to move 100kw of heat energy, but if "scaled right" a simple heat pump can "move more heat" than the amount of "work" being used to move that heat.

And this is your fundamental error.

You have 125 units of waste heat, you move that using a heat pump - to where? Within the closed system or into the open system? Why do you need an energy input, where is the work being done.

In the case of a spacecraft/starship, the waste heat needs to be rejected into the environment (space) ... and you usually can't use conduction/convection (in the normal sense) to do that ... which leaves radiation (see: EM spectrum) and, with sufficient technology, gravitic effects to "reject" waste energy into the external environment (space) around the craft.

At last

Dial up the radiation temperature (photon energies) high enough and you can "squeeze" the waste heat rejection from going in ALL directions to only going in SOME directions (presumably aft of the maneuver drive). You can therefore "trade" the waste heat signature from being the same in all directions to being low in some directions at the expense of it being higher in other directions (see: aft of maneuver drive as an example).

But that can still be detected.

This isn't all that much different from the notion of stealth in aircraft design, where they have different radar return cross-sections depending on the aspect relative to the radar emitter/sensor setup. Frontal stealth can be high, while side/aft stealth might be lower (for example).

Stealth aircraft are easily detected, it is getting a target lock that is difficult.

 

[infojunky]

Ok, We are back.

Stealth in Space is Conditional. Just like real life.

Passive sensors range is limited by their inherent Margin of Error of the receiver and the amount of computer power available.

Couple that with Constant Thrust, it a simple matter to shape the direction of the Heat/Size signature.

Active Sensors will give more reliable results over the perceived combat ranges. Consider this your big passive array receives the know return signal from your active emitter. Further Related is the emitter is frequency agile such as there is not a single know frequency repeated over and over again.

Another note the Submarine model is very flawed for these discussions. The Aircraft model is probably best, followed by the Surface Warfare one.

All of the preposed work around embedded in this topic would work, a variable number of times. Mostly controlled by the experience of the crew in question.

A last note, engineering rather than the "Science" answer is the true limit. Meaning Comparing a scientific instrument on a stable platform, is much different from the one on a moving/vibrating platform. Couple that to how much money the local system is willing/able to spend Early Spacebourne Detection.