I think it's important that they have a face, especially in flight, so that we can rip off ker--er, so that we can relate to our human astronauts more.
@AndrewGarrison I would strongly urge you to use constant thrust power for NTRs for this update. The NTR reactor should be identical between any different propellant modes, there's no reason why the reactor should be nerfed when using heavier propellants.
Are you ever going to implement an alternate thrust/isp calculation for NTRs which preserves Thrust Power instead of Chamber Pressure? (Since the reactor power should be constant, whereas it makes sense to keep chamber pressure constant in a chemical rocket)
@AndrewGarrison Wow, it cut off exactly two letters. What luck.
I can't see any advantage to using waterlogged NTRs unless the thrust is increased. For gameplay reasons the whole point of using water in an NTR is getting that increased thrust. I think it's necessary from a gameplay standpoint.
The same NTR design should have the same thrust power regardless of what's being pumped through it, because that's defined by the temperature and size of the reactor. This may be different among chemical engines, where it would make sense to keep the chamber pressure the same and vary other things (what with different fuels burning at different temperatures), but in an NTR the power is defined by the reactor itself, which is a constant between two NTRs that are otherwise identical.
As far as I can tell, having the waterlogged NTR have the same thrust as the Hydrogen NTR would imply that the thrust power is in fact lower, which shouldn't be the case for an NTR as opposed to a chemical rocket.
@AndrewGarrison Heavier molecular weights will actually result in a higher thrust proportional to the decrease in specific impulse for the same mass flow rate and thrust power. Since the temperature of an NTR reactor is the same as the temperature of the combustion chamber in a hydrolox rocket, and the exhaust products are exactly identical (H2 and O2, the water is torn apart by the NTR), and the turbopumps should be the same, the performance of a water NTR and a Hydrolox rocket should be identical.
Another way of looking at this:
P = 1/2 * T * Ve
P = Thrust power. T = Thrust. Ve = Exhaust Velocity.
The temperature of the reactor is essentially proportional to the thrust power and does not change depending upon the propellant in an NTR. So therefore if you decrease the specific impulse (exhaust velocity) you need to increase the thrust to keep the same thrust power.
"This means, given an NTR and a combustion rocket of similar sizes and similar temperatures, the total power is roughly the same. And if we assume the exhaust velocity of the NTR is roughly twice that of the combustion rocket, the thrust of the NTR must be roughly half that of the combustion rocket. By extension, if the NTR has the same exhaust velocity as the combustion rocket, then the thrust must be the same."
Yet another, simpler way of looking at this:
T = m_dot * ve
T = Thrust. M_dot = Mass flow rate. Ve = Exhaust velocity. Assuming a constant mass flow rate, since we're using about the same pumps in both engines, the thrust and specific impulse are inversely proportional.
"Essentially, this means the biggest advantage of NTRs, their high exhaust velocity, is the root cause of their lower thrust. Additionally, NTRs which do not have this advantage, the high exhaust velocities, have comparable thrust as combustion rockets!"
As I understand it, though of this I am not certain, it would break the laws of thermodynamics for this thrust-thrustpower-efficiency rule to not work the way it does.
This blog post by the hard science simulation game Children of a Dead Earth explains it: https://childrenofadeadearth.wordpress.com/2016/05/27/gasping-for-fumes/
(But the general idea is corroborated by every other source I found back when I first brought the idea up)
I think perhaps adding Methane as a propellant for NTRs might be a good idea. A compromise between H2O and LH2 in both thrust and efficiency. (Especially since we now have Methalox chemical rockets)
The NTR doesn't seem to have increased thrust in water propellant mode. It should have a thrust increased inversely proportional to the decreased specific impulse.
Also I had a thought--it would be nice if we could get water as a propellant for NTRs. Results in hydrolox-like thrust and isp, but with a denser propellant!
@bartekkru100 There's a few factors in exhaust color. If there's soot in the exhaust, then each soot particle will behave as a thermal blackbody, and you'll get a color/temperature relationship that goes red-orange-yellow-white-blue with increasing temperature. Kerolox rockets and methalox rockets have soot, SRBs exhaust is extremely sooty and still burning. If the exhaust is clean, like if it's a hydrogen rocket, then the exhaust will be almost transparent and will condense into water vapor plumes that follow significantly behind the engine. If the nozzle is ablatively cooled, like the RS-68 on the Delta-IV rockets, there will be some orange-red soot in the exhaust, but not nearly as much. NTR rockets will have a completely transparent exhaust. This is because in space, hydrogen exhaust will cool off very quickly, so it will not stay glowing. Again, if you're pumping methane or kerolox through an NTR, then there will be glowing hot soot that eventually cools into black soot.
In some engines, even clean ones, you'll see a faint bluish or orangish glow. I believe this is from the emission spectrum of the exhaust gasses, and is determined by exactly what elements are gaseous in the exhaust and exactly what is happening to the gasses. It's not the normal ionized emission spectrum of hydrogen and oxygen creating that blue color, nor is it the blackbody heat, it's something about the specific chemistry of hydrogen and oxygen turning into water--I don't fully understand this!
https://www.youtube.com/watch?v=aB8knRvUywo This is a video by the beloved dearest lord, Scott Manley, regarding some of this exhaust science.
I like it. One note: In a vacuum, engine exhaust (from any nozzle shape) should be cone-shaped. There's a good blog post about some of the science here from the realistic space wargame Children of a Dead Earth, here: https://childrenofadeadearth.wordpress.com/2016/04/11/why-does-it-look-like-that-part-1/
@Venus I disagree. No gas giants should have atmospheres that aren't blue. I don't mean the clouds, of course those can and should be brown for a jupiter-like planet. In addition, blue atmospheres on a brown planet creates a really quite beautiful somewhat contrasting color scheme. Also, even Venus' sky is blue from above the cloud tops! You can almost see some subtle limb-lighting of blue in your own profile pic.
Hi! I love the progress, the game looks really pretty, and I'm impressed with how it looks and how it appears to work! But I will say one thing: Jupiter (and indeed all of the gas giants) have blue atmospheres, not brown! It's because of rayleigh scattering, which is not unique to nitrogen/oxygen breathing mix. Mars' atmosphere is brown because of the dust, which Jupiter does not have, only clouds.
I hope you will also have the conventional arrow-key type controls (with a stabilizer like KSP's SAS, hopefully) because with only two axes, you can have a problem similar to Dobson's Hold with dobsonian telescopes (using an altitude/azimuth cannon-like aiming scheme). Near the poles of the sphere it can be difficult to point where you want to go. (Similar problem to Gimbal lock) Also, no way to roll! This can be disastrous if you're trying to dock things in space that need precise alignments. So while this may be useful for simple piloting, I would definitely prefer to use a joystick or arrow-key like system.
Also now that we have three dimensions, maybe you could display icons for normal/antinormal and radial/antiradial orbit directions, in addition to prograde/retrograde.
This is still a smartphone game in addition to PC, right? While I think the game COULD compete with KSP on the PC, I am particularly interested in the mobile version.
I noticed a problem. 13,000 celsius is more than enough to glow blindingly bright blue hot and vaporize practically anything. The air in front may have reached 11,000 Kelvins, but I doubt the solid heatshield itself got that hot, it was designed to ablate away. I'm not sure, honestly. But what I do know is that if it did get that hot, it would not be glowing red!
For an example of how color/temperature should be implemented, see https://academo.org/demos/colour-temperature-relationship/ this calculator. (There's a link to the algorithm it uses, although you could just use a color gradient)
The reentry effect looks absolutely gorgeous by the way, consider me extremely impressed by what I've seen.
I think it's important that they have a face, especially in flight, so that we can rip off ker--er, so that we can relate to our human astronauts more.
+5 4.8 years ago@AndrewGarrison I would strongly urge you to use constant thrust power for NTRs for this update. The NTR reactor should be identical between any different propellant modes, there's no reason why the reactor should be nerfed when using heavier propellants.
+2 5.6 years agoAre you ever going to implement an alternate thrust/isp calculation for NTRs which preserves Thrust Power instead of Chamber Pressure? (Since the reactor power should be constant, whereas it makes sense to keep chamber pressure constant in a chemical rocket)
+2 5.6 years ago@AndrewGarrison Wow, it cut off exactly two letters. What luck.
I can't see any advantage to using waterlogged NTRs unless the thrust is increased. For gameplay reasons the whole point of using water in an NTR is getting that increased thrust. I think it's necessary from a gameplay standpoint.
The same NTR design should have the same thrust power regardless of what's being pumped through it, because that's defined by the temperature and size of the reactor. This may be different among chemical engines, where it would make sense to keep the chamber pressure the same and vary other things (what with different fuels burning at different temperatures), but in an NTR the power is defined by the reactor itself, which is a constant between two NTRs that are otherwise identical.
As far as I can tell, having the waterlogged NTR have the same thrust as the Hydrogen NTR would imply that the thrust power is in fact lower, which shouldn't be the case for an NTR as opposed to a chemical rocket.
+1 5.6 years ago@AndrewGarrison I'll get back to you next time I open the game, but I believe it was both the Mage and the Pixie.
EDIT: Default power cycle, methalox on the mage, kerolox on the pixie, and I noticed it on another engine (that I dont remember the specifics of)
+1 5.7 years ago@AndrewGarrison Heavier molecular weights will actually result in a higher thrust proportional to the decrease in specific impulse for the same mass flow rate and thrust power. Since the temperature of an NTR reactor is the same as the temperature of the combustion chamber in a hydrolox rocket, and the exhaust products are exactly identical (H2 and O2, the water is torn apart by the NTR), and the turbopumps should be the same, the performance of a water NTR and a Hydrolox rocket should be identical.
Another way of looking at this:
P = 1/2 * T * Ve
P = Thrust power. T = Thrust. Ve = Exhaust Velocity.
The temperature of the reactor is essentially proportional to the thrust power and does not change depending upon the propellant in an NTR. So therefore if you decrease the specific impulse (exhaust velocity) you need to increase the thrust to keep the same thrust power.
"This means, given an NTR and a combustion rocket of similar sizes and similar temperatures, the total power is roughly the same. And if we assume the exhaust velocity of the NTR is roughly twice that of the combustion rocket, the thrust of the NTR must be roughly half that of the combustion rocket. By extension, if the NTR has the same exhaust velocity as the combustion rocket, then the thrust must be the same."
Yet another, simpler way of looking at this:
T = m_dot * ve
T = Thrust. M_dot = Mass flow rate. Ve = Exhaust velocity. Assuming a constant mass flow rate, since we're using about the same pumps in both engines, the thrust and specific impulse are inversely proportional.
"Essentially, this means the biggest advantage of NTRs, their high exhaust velocity, is the root cause of their lower thrust. Additionally, NTRs which do not have this advantage, the high exhaust velocities, have comparable thrust as combustion rockets!"
As I understand it, though of this I am not certain, it would break the laws of thermodynamics for this thrust-thrustpower-efficiency rule to not work the way it does.
This blog post by the hard science simulation game Children of a Dead Earth explains it: https://childrenofadeadearth.wordpress.com/2016/05/27/gasping-for-fumes/
(But the general idea is corroborated by every other source I found back when I first brought the idea up)
I think perhaps adding Methane as a propellant for NTRs might be a good idea. A compromise between H2O and LH2 in both thrust and efficiency. (Especially since we now have Methalox chemical rockets)
I hope this clears some thin
+1 5.7 years agoThe new rocket engine sound loop has an extremely annoying repetitive sound in it that the sounds did not have previously.
5.7 years agoThe NTR doesn't seem to have increased thrust in water propellant mode. It should have a thrust increased inversely proportional to the decreased specific impulse.
+1 5.7 years ago@SupremeDorian Atompunk meets Steampunk!
5.7 years agoAlso I had a thought--it would be nice if we could get water as a propellant for NTRs. Results in hydrolox-like thrust and isp, but with a denser propellant!
5.7 years ago@bartekkru100 There's a few factors in exhaust color. If there's soot in the exhaust, then each soot particle will behave as a thermal blackbody, and you'll get a color/temperature relationship that goes red-orange-yellow-white-blue with increasing temperature. Kerolox rockets and methalox rockets have soot, SRBs exhaust is extremely sooty and still burning. If the exhaust is clean, like if it's a hydrogen rocket, then the exhaust will be almost transparent and will condense into water vapor plumes that follow significantly behind the engine. If the nozzle is ablatively cooled, like the RS-68 on the Delta-IV rockets, there will be some orange-red soot in the exhaust, but not nearly as much. NTR rockets will have a completely transparent exhaust. This is because in space, hydrogen exhaust will cool off very quickly, so it will not stay glowing. Again, if you're pumping methane or kerolox through an NTR, then there will be glowing hot soot that eventually cools into black soot.
In some engines, even clean ones, you'll see a faint bluish or orangish glow. I believe this is from the emission spectrum of the exhaust gasses, and is determined by exactly what elements are gaseous in the exhaust and exactly what is happening to the gasses. It's not the normal ionized emission spectrum of hydrogen and oxygen creating that blue color, nor is it the blackbody heat, it's something about the specific chemistry of hydrogen and oxygen turning into water--I don't fully understand this!
https://www.youtube.com/watch?v=aB8knRvUywo This is a video by the beloved dearest lord, Scott Manley, regarding some of this exhaust science.
+2 5.7 years agoI like it. One note: In a vacuum, engine exhaust (from any nozzle shape) should be cone-shaped. There's a good blog post about some of the science here from the realistic space wargame Children of a Dead Earth, here: https://childrenofadeadearth.wordpress.com/2016/04/11/why-does-it-look-like-that-part-1/
+2 5.7 years ago@AndrewGarrison I did not. Did you get mine that I sent yesterday?
6.1 years ago@NathanMikeska Thanks.
6.1 years ago@Bmcclory what about the mobile app?
6.3 years ago@Venus I disagree. No gas giants should have atmospheres that aren't blue. I don't mean the clouds, of course those can and should be brown for a jupiter-like planet. In addition, blue atmospheres on a brown planet creates a really quite beautiful somewhat contrasting color scheme. Also, even Venus' sky is blue from above the cloud tops! You can almost see some subtle limb-lighting of blue in your own profile pic.
+1 6.3 years agoHi! I love the progress, the game looks really pretty, and I'm impressed with how it looks and how it appears to work! But I will say one thing: Jupiter (and indeed all of the gas giants) have blue atmospheres, not brown! It's because of rayleigh scattering, which is not unique to nitrogen/oxygen breathing mix. Mars' atmosphere is brown because of the dust, which Jupiter does not have, only clouds.
6.3 years agoI hope you will also have the conventional arrow-key type controls (with a stabilizer like KSP's SAS, hopefully) because with only two axes, you can have a problem similar to Dobson's Hold with dobsonian telescopes (using an altitude/azimuth cannon-like aiming scheme). Near the poles of the sphere it can be difficult to point where you want to go. (Similar problem to Gimbal lock) Also, no way to roll! This can be disastrous if you're trying to dock things in space that need precise alignments. So while this may be useful for simple piloting, I would definitely prefer to use a joystick or arrow-key like system.
Also now that we have three dimensions, maybe you could display icons for normal/antinormal and radial/antiradial orbit directions, in addition to prograde/retrograde.
This is still a smartphone game in addition to PC, right? While I think the game COULD compete with KSP on the PC, I am particularly interested in the mobile version.
6.3 years agoI noticed a problem. 13,000 celsius is more than enough to glow blindingly bright blue hot and vaporize practically anything. The air in front may have reached 11,000 Kelvins, but I doubt the solid heatshield itself got that hot, it was designed to ablate away. I'm not sure, honestly. But what I do know is that if it did get that hot, it would not be glowing red!
For an example of how color/temperature should be implemented, see https://academo.org/demos/colour-temperature-relationship/ this calculator. (There's a link to the algorithm it uses, although you could just use a color gradient)
The reentry effect looks absolutely gorgeous by the way, consider me extremely impressed by what I've seen.
+2 6.4 years ago