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Subject: 3rd ed. lander burns = extreme fuel consumption? rss

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Hi all,

I'm trying to understand fuel consumption crossing the 3rd edition lander burn markers. I'm specifically thinking about landing on Mars, but it's also the general principle.

In 3rd edition, my understanding of how a landing on Mars would work is this:

Let's say you have a Delaval Nozzle thruster (5,1) and the NASA crew thruster (10,8) in a rocket orbiting Mars. You're in LMO, and there is a full lander burn marker between you and the surface.

In 3rd ed., do you have to cross the lander burn between LMO and the Martian surface using the NASA crew thruster, and thus spend 8 fuel to land? Or can I use the Delaval to spend 1 fuel, but I need to have the NASA crew thruster present to make the landing? If the former, it seems like all the terrestrial planets are now fuel-hungry rocket traps.

In 2nd ed., you'd park in LMO for a turn, begin the next turn with NASA as your active thruster, and land for no fuel. For the 2nd ed. rules, I thought this post (https://boardgamegeek.com/thread/584956/zero-fuel-landings-e...) gave a pretty good explanation for why landing / launch required no fuel expenditure if you thrust was higher than the site size.
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Charlie Mote
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There's definitely been a rule change, although I don't think I understand it well enough to explain.

I do know that the reason was to better approximate reality - there was a pretty big leap made in the approximations in previous editions. There was much discussion over this point in the creation of the third edition and I thought the logic and reasoning was very sound. The reality is, compared to all other travel in the solar system, the deep gravity wells are just that.
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Rich James
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Since you are not allowed to stop in lander burns, you will need enough thrust to land safely on Mars and your Delaval Nozzle thrust doesn't have that. So you will need to use your crew card to pass through the lander burn and then land on Mars (if you are not trying an aerobrake landing).

Yes, the gravity well is deep. The lander burns bring symmetry to landing and takeoff that was missing in 2nd edition.
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Francisco Colmenares
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tgbeatty wrote:
Hi all,

I'm trying to understand fuel consumption crossing the 3rd edition lander burn markers. I'm specifically thinking about landing on Mars, but it's also the general principle.

In 3rd edition, my understanding of how a landing on Mars would work is this:

Let's say you have a Delaval Nozzle thruster (5,1) and the NASA crew thruster (10,8) in a rocket orbiting Mars. You're in LMO, and there is a full lander burn marker between you and the surface.

In 3rd ed., do you have to cross the lander burn between LMO and the Martian surface using the NASA crew thruster, and thus spend 8 fuel to land? Or can I use the Delaval to spend 1 fuel, but I need to have the NASA crew thruster present to make the landing? If the former, it seems like all the terrestrial planets are now fuel-hungry rocket traps.

In 2nd ed., you'd park in LMO for a turn, begin the next turn with NASA as your active thruster, and land for no fuel. For the 2nd ed. rules, I thought this post (https://boardgamegeek.com/thread/584956/zero-fuel-landings-e...) gave a pretty good explanation for why landing / launch required no fuel expenditure if you thrust was higher than the site size.

In 3rd edition you have to use the NASA crew thruster and spend 8 steps. Please note , that even in 2nd edition if you were taking off the planet you would still have to use the NASA crew thruster since you're not allowed to "switch" thrusters mid-flight. This led to asymmetry in taking off/landing since in 2nd edition you were allowed to "park" in the middle of a gravity well.

As another poster mentioned this rule streamlines take off and landing and brings symmetry to the maneuver. Compared to 2nd edition.
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Pawel Garycki
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How to handle gravity wells? Supposing you don't have 10-8 crew with you.
- consider another location, really; late in the game, with a good buggy and assying smelters you may choose a smaller asteroid instead - why bother with gravity wells? Even early in the game you can maake a good use of your crew's laser (ventures, tiny moon prospecting) or buggy (comets!)
- try to acquire Project Orion
- use aerobrakes to avoid lander burns
- for Mars, consider acquiring Elevator glory and then use it for ascent
- Mosquito is a good 10-8 white card thruster and isru device
- on Mercury some solar powered generators, beaming fro powersat and relatively good thrusters may allow you to land and lift off even if it is not possible in another worlds
- remember on Venus and gas giants there are aerostat ascents so you don't need high thrust
- hire colonists with a decent thrust, some of them may also provide 10-4
- if using Exploration Module, hire a mercenary crew with 10-8
- you don't need thrust to missile-bombard enemy player's site
- some black cards may increase your thruster's thrust, especially reactors
- GW/TW thrusters may do it unless if using Simulation rules
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Dom Rougier
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"Planetary chauvinism" is a useful term here, usually credited to Asimov.

Usually, you end up spending *less* fuel in 3rd edition High Frontier in deep gravity wells, since there are now more powerful chemical thrusters... but planetary chauvinism is the (possible) fallacy that the planets are the important bodies in the solar system.

Mars is particularly interesting with the Colonist module. As a site in general it has a lot to be desired - the C spectral type is not particularly valuable, and the energy required to get in and out of the gravity well is excessive.

Where Mars has an advantage, it's that it's big, close and wet. This makes it one of the best (if not the best) site to colonise in the game, and one of the best ways to score futures that rely on having a large number of colonists.
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Geoff Speare
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I am certainly not an expert at this game so am probably getting something wrong here.

Using 2nd edition map and rules (rules from Dec 7 2013, map from BGG), there's a burn into Mars HEO, a 2nd burn into Mars LEO, and then landing, for which nothing would be paid assuming a large enough thruster.

Using 3rd edition map and rules (rules from the box, map from BGG), there's a burn into what I assume is Mars HEO, Mars LEO is free, and then a 2nd landing burn which you can't get out of.

Either way it's two burns to land (assuming the proper thruster), right?

 
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Francisco Colmenares
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galfridus wrote:
I am certainly not an expert at this game so am probably getting something wrong here.

Using 2nd edition map and rules (rules from Dec 7 2013, map from BGG), there's a burn into Mars HEO, a 2nd burn into Mars LEO, and then landing, for which nothing would be paid assuming a large enough thruster.

Using 3rd edition map and rules (rules from the box, map from BGG), there's a burn into what I assume is Mars HEO, Mars LEO is free, and then a 2nd landing burn which you can't get out of.

Either way it's two burns to land (assuming the proper thruster), right?


The difference is that in 3rd edition, the last burn is a lander burn, meaning you can't stay in the space. In second edition you could use the DeLaval (5-1, or was it a 5-2? Assume 5-1 for sake of argument) to go two burns, stop, and then in the next turn use a high thrust inefficient booster (say the 9-6 missile robonaut powered by Orion giving it a 13-6) and land.

In third edition you can't do that anymore. You can stop in LMO after using your 5-1 thruster but to land you need the high thrust of the Orion-powered missile robonaut and incur the high cost of making the fuel burn and land.

Note that in both 2nd and 3rd edition you would not be able to take off with the DeLaval, you would need to use the Orion-powered robonaut to get off and pay for the fuel burn.

As you can see the lander burn makes it so that landing on a site with a large gravity well requires the same effort as taking off from it. No more cheating on the landing by stopping just short of the site and switching thrusters the following turn.
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Victor Caminha
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Francisco, I havent got my copy and havent read the online rules, but I would like to ask:

- Since you cant stop on lander burns, and I have a chemical rocket 10*8 resting at a standard burn right before a lander burn to Mars, I will need to spend 8 steps of fuel/propellant to land and then 16 steps to leave the site, the lander burn and arrive at the adjacent standard burn before I have a chance to switch to a more economic thruster?
 
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Dom Rougier
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Two burns out is about right, assuming you're not getting any help from the atmosphere via aerobraking.

Quote:
Each BURN or lander burn requires a delta-v (velocity change) of
2.5 km/sec. Each PIVOT (brachistochrone maneuver) is 5.0 km/
sec and a distance of about 2 AU.


From a dV map approximation:



3.8 + 0.70 + 0.40 + 0.34 = 5.24 km/s, or two burns. With inefficient chemical thrusters (10.8), this will be 16 steps of fuel, with the likely addition of two more steps to end up with a modified thrust > 10 with the use of the afterburner.

All three Mars sites in the third edition have the option of landing for free with aerobraking, and Mars can be reached/landed on for as little as two burns heading out, with sensible use of flybys (this usually increase the energy of the encounter, and adds another aerobrake, so it's riskier).
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Victor Caminha
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Thanks for explaining! I also forgot to add the need to afterburn to get a Higher thrust value than the gravity well of 10
 
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It's worth mentioning with this kind of thing that High Frontier starts at a larger scale than present spacecraft. With the new fuel strip it becomes possible to some some smaller scale stuff than was done previously, but it's still a fairly blunt instrument when it comes to replicating Apollo or similar missions.

The Saturn V could put 120 tons (3 mass points) into LEO, but that would shoot 40 tons (1 mass) to the Moon - in game terms that subdivides, since the Lunar Module was something like 15 tons, which is far below High Frontier's scale.

In High Frontier, each Crew module is 40 tons, which is an awful lot to take down to the surface and back. Curiosity is the heaviest payload landed on Mars at the moment, and that's only one ton.
 
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Victor Caminha
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While we are talking about it, in 2e you calculated thrust after spending fuel when taking off a site. In 3E, do you first spend the lander burn then check for your total thrust to see if the rocket can land at a site?
 
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Nope, looks like this is simplified now.

The only exceptions are for Aerobraking, Factory assisted landing and taking off, and Aerostats (zeppelins!).
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Got it. And I was wondering if the Aerostats would have a special rule for landing/takeoff
 
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Francisco Colmenares
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Hi Viktor.

LMO (Low Mars Orbit) is now an L-Spot with no burn. Basically there is indeed a spot you can park between the Mars Lander burn and the Next regular burn you need to escape Mars orbit. So its 8 steps plus afterburner to land and the same to take off. Check the image gallery for the 3rd edition map.
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Thanks, Francisco, I'm sure those who follow Matt Damon footsteps will be relieved on seeing that.
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Quite right - there's one burn to LMO, and one burn to reach Mars escape - when you said the "adjacent burn", I assumed that's the one you meant.

This does mean you could, for example, leave a return vehicle in low orbit with fuel, waiting for the lander to return.
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Pawel Garycki
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Domfluff wrote:
In High Frontier, each Crew module is 40 tons, which is an awful lot to take down to the surface and back.

Not true. B612 crew has 0 mass (but at a cost of decreased rad hardness). It is then more similar to Apollo.
 
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Ah true, but it's still true for most of them
 
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I wonder if Earth had 11 size how would a start from its surface to LEO look like in High Frontier? I assume 2 lander burns to LEO. With that, full escape from Earth would have 4 burns, similar to Venus.
However lifting off with 10-8 thruster would be difficult at size 11. The crew engine is designed to use water but the heavy Earth thrusters often rely on solid rockets or another kind of liuquid fuel (e.g. nafta). Would it be possible in High Frontier to lift off Earth with just a crew's thruster and water fuel? If not, it must be assumed either lifting off with additional boosters (what would boosters look like in HF? 12-10?) or assembly in space after delivery of small parts with small rockets.
 
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Most launches from Earth in High Frontier will be using two stage, heavy lift launch vehicles. Anything with a 40+ ton payload to LEO, which puts the start date to about five-ten years in the future, at the earliest.

The crew cards use vacuum-optimised chemical thrusters. 2nd edition has this at 6 efficiency, which would have to be hydrolox thrusters at something like the maximum possible efficiency (~450 seconds isp).

With efficiency 8, I'd guess that the intent was to represent methalox (~377s) or kerolox (~357s) in idealised, vacuum form. Since Mars is an important consideration in High Frontier, I'd guess the former is more common.

Staging "cheats" the rocket equation in a sense:

dV to LEO is about 10km/s, so there would be *four* lander burns. To represent this you'd want to have a more granular simulation, but assuming these existed, you'd have to allow the dropping of chemical boosters halfway through.

Earth would be size 12 (Mars is about 1/4 Earth gravity, each size point doubles surface gravity.)

The Saturn V on the launchpad massed something like 2,950 metric tons, or about 74 Mass in High Frontier terms. This puts 3 Mass into orbit, and 1 Mass to the Moon. Obviously this breaks the fuel strip, but you can see how the vast majority of that would be fuel.
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improove wrote:
I wonder if Earth had 11 size how would a start from its surface to LEO look like in High Frontier? I assume 2 lander burns to LEO. With that, full escape from Earth would have 4 burns, similar to Venus.
However lifting off with 10-8 thruster would be difficult at size 11. The crew engine is designed to use water but the heavy Earth thrusters often rely on solid rockets or another kind of liuquid fuel (e.g. nafta). Would it be possible in High Frontier to lift off Earth with just a crew's thruster and water fuel? If not, it must be assumed either lifting off with additional boosters (what would boosters look like in HF? 12-10?) or assembly in space after delivery of small parts with small rockets.

Take into account Venus is an aerostat site. You're not landing ON Venus.

I believe Phil at one point said that from Earth Surface to LEO is 4 burns (~= 10km/s).
 
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colmenarez wrote:
improove wrote:
I wonder if Earth had 11 size how would a start from its surface to LEO look like in High Frontier? I assume 2 lander burns to LEO. With that, full escape from Earth would have 4 burns, similar to Venus.
However lifting off with 10-8 thruster would be difficult at size 11. The crew engine is designed to use water but the heavy Earth thrusters often rely on solid rockets or another kind of liuquid fuel (e.g. nafta). Would it be possible in High Frontier to lift off Earth with just a crew's thruster and water fuel? If not, it must be assumed either lifting off with additional boosters (what would boosters look like in HF? 12-10?) or assembly in space after delivery of small parts with small rockets.

Take into account Venus is an aerostat site. You're not landing ON Venus.

I believe Phil at one point said that from Earth Surface to LEO is 4 burns (~= 10km/s).


From a physics point of view, landing on / taking off from the following three locations discussed in this thread is approximately identical:

(a) Venus aerostat
(b) surface of Venus
(c) Earth surface

In all the above cases:

1. You need ~3 burns (4 if you fight drag and other inefficiencies) of delta-V between site location and low orbit.

2. These 3-4 burns need to be executed with thrust higher than the weight of your rocket (if you are not using aerobraking/aerostat tricks), or your rocket won't be capable of supporting its own weight when taking off or soft landing.

3. You can use aerobraking to bleed off all the delta-Vs for landing, or the (implied) "aerodynamic airship" for lift-off, which cancels out your weight so you no longer need high thrust to reach orbit (but you still need to do the burns).

Edit: for that matter, you should be able to aerostat into orbit from Mars surface as well, but I guess that was omitted from Mars for balance purposes. Or rather, it was included for Venus and the other aerostat sites for balance purposes. Maybe one of the playtesters can comment. The aerodynamic airship capable of reaching orbital velocities is admittedly a bit of a thematic stretch because: (a) it is one of the most speculative technologies in HF; (b) you have to imagine that your rockets always include a mass 0 aerodynamic airship which they deploy when taking off from aerostat sites. [A houserule might be to have an actual aerodynamic airship card which has some mass, perhaps a black refinery.]
 
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