HEPlaR question...(using it for launches/landings)

[Tellon]

Now I know the way it is in TNE -- makes it very unrealistic for fuel usage -- and people screamed about it needing a x5 or x6 for consumption --

so for me -- I will use x5 cons from TNE stats here ..

so TL10 Fusion engine -- to get our heat; say we have a 5000 ton ship (loaded wt)

but for what I want -- 2G launches -- I want a 10,000 ton HEPlaR

so ...

500 MW
50 kl
50 tons
.5 Mcr

F.cons: 1.25 x 500 = 625 kl/hr of launch/landing = 10.4167 kl/min
Hull Suf: TT/200 = 50 sq met

So then on a size 8 world @ 2G ---> 8.5 min to LPO (88.54167 kl used to get to LPO)
(see Hard Times chart on pg 86)

so for LPO Mods (see Hard Times pg 87)
-- so we'll say that our planet was a Dense atmosphere (9+) -- so with a Mod of 1.2 for such a thick atmosphere --

8.5 x 1.2 = 10.2 min to LPO -- thus -- F.cons -> 106.25 kl to get to LPO

Edit: since LPO requires station keeping -- we want to get to SPO (stable planetary orbit) -- so LPO x 1.3

thus our size 8, Atm 9+ world which took 10.2 min to get to LPO -- we then take an added 3.06 min to get to SPO. So a total of 13.26 min to get from direct launch to SPO (using 138.1254 kl of fuel)

-----

So then here is my question --

Is this a viable way to do a "low TL" launch/land process -- or is HEPlaR just too broken.

 

[atpollard]

If you want 'realistic' reaction drives to orbit, then assume that at TL 6 a ship requires about 90 percent of the mass to be "fuel/reaction mass". For each TL after 6, assume that the percentage of fuel drops by 10 percent (ie, 90% @ TL 6; 80% @ TL 7; 70% @ TL 8; 60% @ TL 9; 50% @ TL 10).
Then feel free to assign names to each of the TL rocket engines.

The critical issue is the need to conserve momentum. As the fuel/reaction mass decreases, the exhaust velocity increases, the engine becomes hotter and the exhaust becomes more dangerous (ie. like a weapon blasting a crater in the ground on takeoff).

Good luck,
Arthur

[Sorry, but I am too unfamiliar with TNE to comment directly on the rules and your proposed change, these figures are based on optimistic real world potential ISP values (including questionable things like the nuclear light bulb or magnetic bottle engines).]

 

[Tellon]

If you want 'realistic' reaction drives to orbit, then assume that at TL 6 a ship requires about 90 percent of the mass to be "fuel/reaction mass". For each TL after 6, assume that the percentage of fuel drops by 10 percent (ie, 90% @ TL 6; 80% @ TL 7; 70% @ TL 8; 60% @ TL 9; 50% @ TL 10).
Then feel free to assign names to each of the TL rocket engines.

The critical issue is the need to conserve momentum. As the fuel/reaction mass decreases, the exhaust velocity increases, the engine becomes hotter and the exhaust becomes more dangerous (ie. like a weapon blasting a crater in the ground on takeoff).

Yes, I am familiar with the usage of fuel -- since your using so much -- you actually loose a lot of weight and so speed differences occur ... which is why Chem/LOX rockets had stages -- due to differing G-speeds and fuel reqs needed.

But I am curious of HEPlaR itself --

------

as far as the heat of the plasma "torch" -- yeah -- I am familiar of the ground being turned into lava due to the heat of the exhaust ... But then again -- I dont think Canaveral replaced the launch pads everytime there was a launch -- And all those Mercury/Gemini/Apollo missions had to have had some sort of effect .. right?

And a Saturn V has a HUGE launch exhaust -- I dont see the towers and pad melting due to the heat of the exhaust .. Or what about all those Shuttle take-offs -- still the same kind of Chem/LOX + Booster style launches.

So then -- if the launch doesn't melt it -- why would a landing?

 

[Tellon]

I'm looking thru various forums and googling info to see if just the fuel consumption was the big gripe on HEPlaR's. And it looks like by jacking up the F.cons -- that it looks to be good to use for a lot of folks .. lol

I chuckled when I saw 1 player worry about having to constantly look at the fuel gauge with HEPlaR's .. lol

so ... HEPlaR seems to be used by a LOT of folks doing designs and for different systems .. especially TNE, T20, CT/MT.

And like what other folks have seemingly noted -- it's a "kind" of Fusion torch -- so thus -- it should only be used say in a vacuum or planet without life -- otherwise it would be considered an act of war ... (due to the damage it could cause to the area)

---

So generally just re-checking what others have said about HEPlaR's -- Made sure to stop by traveller.mu.org and check out the archives .. since there is a heck of a lot of good info there.

 

[robject]

If you want 'realistic' reaction drives to orbit, then assume that at TL 6 a ship requires about 90 percent of the mass to be "fuel/reaction mass". For each TL after 6, assume that the percentage of fuel drops by 10 percent (ie, 90% @ TL 6; 80% @ TL 7; 70% @ TL 8; 60% @ TL 9; 50% @ TL 10).
Then feel free to assign names to each of the TL rocket engines.

Can this be tuned a bit for winged craft? Won't they require less fuel to climb, say, the first ten miles or so? Or is that insignificant in the big, orbital, scheme of things?

Also, perhaps, consider that a launch booster type of system might come into play -- you know, sort of a massive JATO or something which detaches and reenters when expended, which does not count towards the ship's orbital system as a whole...

 

[Andrew Boulton]

And like what other folks have seemingly noted -- it's a "kind" of Fusion torch -- so thus -- it should only be used say in a vacuum or planet without life -- otherwise it would be considered an act of war ... (due to the damage it could cause to the area)

The TNE air/raft used it! :toast:

 

[aramis]

I'm looking thru various forums and googling info to see if just the fuel consumption was the big gripe on HEPlaR's. And it looks like by jacking up the F.cons -- that it looks to be good to use for a lot of folks .. lol

I chuckled when I saw 1 player worry about having to constantly look at the fuel gauge with HEPlaR's .. lol

so ... HEPlaR seems to be used by a LOT of folks doing designs and for different systems .. especially TNE, T20, CT/MT.

And like what other folks have seemingly noted -- it's a "kind" of Fusion torch -- so thus -- it should only be used say in a vacuum or planet without life -- otherwise it would be considered an act of war ... (due to the damage it could cause to the area)

---

So generally just re-checking what others have said about HEPlaR's -- Made sure to stop by traveller.mu.org and check out the archives .. since there is a heck of a lot of good info there.

TNE G-burns are 30 minutes as I recall. changing the rate to 3 minutes makes it much more reasonable for a thermal rocket.

 

[Tellon]

The TNE air/raft used it! :toast:

no kiddin --

ah well -- I guess a bit of handwavium is good for SciFi ..

:toast:

 

[Tellon]

TNE G-burns are 30 minutes as I recall. changing the rate to 3 minutes makes it much more reasonable for a thermal rocket.

3 min? .. yeah, that would be better for such a fuel hog such as LF,SF, MFD,HEPlaR, FR and others.

Yeah, looking at the archives (glad I did) -- a few things brought up by the guys on MU

F.cons is huge -- for all sub-TL 9 stuff ..
TT is usually made a lot better than it actually was in real terms

Here is the main link for some realistic looks at how the rockets need to be tweaked.
http://traveller.mu.org/house/thrusters.html

So obviously F.Cons is gonna be HUGE -- (take any good Chem rocket launch) -- which is why anything for a rocket, HEPlaR, or sub-9 drives will be used for launch/landing alone -- as why Fuel usage is measured in minutes rather than hours or days .. lol

so ultimately -- HEPlaR is not craziness -- just an "advanced" version of the MPD that we see now ... but it needs realistic tweaks to get it "realistic" and workable for use in a design ...

 

[Tellon]

lol -- I just had to tweak and figure it out -- and I looked at this again from the archives -- and it dawned on me ..

"According to FFS, 1 MW HePlaR thruster consumes 0.25 m3 of liquid hydrogen in one hour. This amount can be converted to (0.25 m3 * 0.07 ton/m3 *1000 / 3600 s =>) 0.0049 kg/s.

Thrust: F = v * m/t [Newtons]
Power consumed by generated thrust: P = 0.5 * m/t * v^2 [Watts]
m/t = 0.0049 kg/s

Thrust in Newtons can be converted to tons by dividing the Newton value by (9.81 m/s^2 * 1000 =>) 9810.

With 1 MW input power and 100% efficiency, the exhaust velocity of plasma is:
v = sqrt(P/(0.5 * m/t)) = 20284 m/s

Thrust produced by this plasma stream is:
F = v * mt / 9810 = 0.0101 tons = 10.1 kg thrust

However, according to FFS, this thrust should be 20 tons, which is 1980.2 times the calculated value."

So then --

I decided to see what the F.cons would be for a realistic 20 TT. So -- .25 x 1980 = 49,500 kl/hr for 20 TT -- so for my 10,000 tons vessel -- it would need 24,750,000 kl of fuel -- or 412,500 kl/min

I can see why I dont have any old designs using HEPlaR -- now I understand why .. lol

 

[atpollard]

as far as the heat of the plasma "torch" -- yeah -- I am familiar of the ground being turned into lava due to the heat of the exhaust ... But then again -- I dont think Canaveral replaced the launch pads everytime there was a launch -- And all those Mercury/Gemini/Apollo missions had to have had some sort of effect .. right?

And a Saturn V has a HUGE launch exhaust -- I dont see the towers and pad melting due to the heat of the exhaust .. Or what about all those Shuttle take-offs -- still the same kind of Chem/LOX + Booster style launches.

So then -- if the launch doesn't melt it -- why would a landing?

You are not properly understanding the temperature differences involved. Thrust is not the issue, a burning match and a forest fire are both roughly the same temperature (think of this as the modern chemical rockets). Molten steel or molten lava is much hotter (think of this as nuclear rocket engines). The surface of the sun is much hotter still (think of this as electric propulsion or HEPlaR). A concrete launch pad can easily survive multiple forest fires. An improved pad might be able to survive molten lava. Nothing survives the surface of the sun.

Obviously the craft can land like the shuttle so the thrust does not point down, I was only trying to say that as the velocity and temperature increases, it becomes more dangerous to stand behind the engine. The ultimate reaction drive is a laser or particle accelerator.

 

[atpollard]

Can this be tuned a bit for winged craft? Won't they require less fuel to climb, say, the first ten miles or so? Or is that insignificant in the big, orbital, scheme of things?

Also, perhaps, consider that a launch booster type of system might come into play -- you know, sort of a massive JATO or something which detaches and reenters when expended, which does not count towards the ship's orbital system as a whole...

Absolutely!!
For a Nuclear Thermal engine, the atmosphere provides free propellant/fuel. As a quick and dirty guess, I'd suggest that the craft can accelerate to half of orbital velocity before it needs to start burning fuel.

As an absolute minimum, I would reduce the required fuel by 25%.

 

[Whipsnade]

The ultimate reaction drive is a laser or particle accelerator.

AT,

Hence the Kzinti Lesson.

I'd also like to point out that the Apollo launchpads, and perhaps the others, had huge quantities of water pumped across them during lift-off. That's why those huge clouds form.


Regards,
Bill

 

[Lycanorukke]

Absolutely!!
For a Nuclear Thermal engine, the atmosphere provides free propellant/fuel.

They tried that with Project Pluto and the Tory-IIC nuclear ramjet which generated 35000 pounds of thrust, with exhauts temps of roughly 1600C. The Tory-III was expected to hit Mach 4 though the project was cancelled before then.

The main problems were the reactor was unshielded, the noise and that ICBM tech advanced. So if one of those flew overhead you would rupture your eardrums, glow in the dark and be roasted alive.

I'd also like to point out that the Apollo launchpads, and perhaps the others, had huge quantities of water pumped across them during lift-off.

The Baikonur pads do, but due to the design of the Russian blast trenches the steam/exhaust blows out the side instead of "sideways then up" as in Canaveral launches so there tends to be somewhat less clouds visible at 'launch level'. The ESA spaceport in French Guinea has 1500m^3 water tanks to cool the pad, but again they blast it out the side.

I was vaguely curious as to why the differences in pad design, and IIRC I think it was due to the Florida site being unable to dig deep "sideways trenches" due to the high water table. Wether or not this is true I can't say.

 

[Tellon]

A concrete launch pad can easily survive multiple forest fires. An improved pad might be able to survive molten lava. Nothing survives the surface of the sun.

Obviously the craft can land like the shuttle so the thrust does not point down, I was only trying to say that as the velocity and temperature increases, it becomes more dangerous to stand behind the engine. The ultimate reaction drive is a laser or particle accelerator.

Ok, cool -- thx

Then what does one do with a Highport? Would space have the same issue as an atmospheric launch/landing pad

 

[Tellon]

They tried that with Project Pluto and the Tory-IIC nuclear ramjet which generated 35000 pounds of thrust, with exhauts temps of roughly 1600C. The Tory-III was expected to hit Mach 4 though the project was cancelled before then.

The main problems were the reactor was unshielded, the noise and that ICBM tech advanced. So if one of those flew overhead you would rupture your eardrums, glow in the dark and be roasted alive.

I guess then the best for low-TL launches is to use AZHRAE (since it's TJ, RJ, Rkt) -- so a hybrid engine from what I can tell ... able to make a small payload shuttle to go from surface to a highport, dump off the cargo and head back down.

Since then, even the Fusion RJ/Rkt used for planes would have the same issue -- plasma plumes in the atmosphere. Even if the planet didn't have an atmosphere -- using an NTR or Fusion RJ/Rkt would still have major issues then .. ... hmmm

 

[shadowdragon]

I am curious (yellow ), where does the idea that HEPlaR creates radiation and extreme temperatures come from? I understand that a fusion torch could create such, but nowhere in the description for HEPlaR does it say the plasma is brought to the point of fusion. It states in FF&S that hydrogen is heated to a plasma state, but does not state the method used. It seems to me that a plasma created with high electron temperatures but a relatively cool ion state could easily be a relatively "cool" exhaust, even though it is technically a high temperature plasma.

The other thing is that even with the high exhaust velocity, I cant see protons and electrons (on an individual basis as would be the case using hydrogen fuel) having sufficient kinetic energy levels to cause a kilometers long plume when they are impacting larger atoms of N2, O2, CO2 and H2O, (or any other atmosphere components for that matter) as some have suggested would be the case, and in an atmosphere the energy used when the electrons and protons recombine plus the cooling effects of the atmosphere itself would lower the plasma temperature fairly quickly. You would still have a nice hot exhaust, hotter than a jet engine or a rocket engine certainly, but not unmanageable I would think.

As far as the thrust issues- I wonder if the error comes from thinking of HEPlaR as a rocket engine. Would considering it a self contained jet engine change any of the thrust generation equations? Unfortunately I was chasing a rather profound (for me) thought on this subject last night but I seem to have lost it....:frankie:

Am I completely off base here?

 

[aramis]

Any particle beam at 0.1C or better creates significant secondary radiation the moment it impacts solids or dense liquids.

the HEPla in HEPlaR is "High Energy Plasma"... and the needed force is significant fractions of C to get the fuel rates shown. So whatever is behind it is getting hit with a CPAWS. Which is going to have the effect of causing them to have cascade secondary radiation when it hits. Basic atomic physics, Shadowdragon.

 

[Tellon]

Thx Aramis -- I wasn't sure how to reply why HEPlaR was so bad --

-- I do Geology and Microbiology -- not Physics .. lol

 

[shadowdragon]

forgot about secondary effects after impact..doh