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Old 07-26-2021, 01:58 PM   #1
MaryAnn
 
Join Date: Aug 2020
Default Spaceships: How to take off?

Most systems have horrendous acceleration in G. In addition, decent acceleration systems have an awful delta-V in mps. What system is the best to take off from Earth without dropping nuclear bombs on the task (Orion Drives)?
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Old 07-26-2021, 02:05 PM   #2
Fred Brackin
 
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Default Re: Spaceships: How to take off?

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Originally Posted by MaryAnn View Post
Most systems have horrendous acceleration in G. In addition, decent acceleration systems have an awful delta-V in mps. What system is the best to take off from Earth without dropping nuclear bombs on the task (Orion Drives)?
HEDM is first, Nuclear Thermal Rocket is second and Antimatter Thermal Rocket is third for reason of fuel cost if nothing else. With unlimited budgets you might get a little bettter fuel enconomy with the Ram-Rocket option.

Oh, there was an lmplied bias against Superscience! drives in your post (also one about takign off from Earth) so I assumed you didn't want those. Reactionless Thrusters (above Rotary) are usable if Superscience! is allowed and Contragravity makes lift-off with almost anything possible.
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Old 07-26-2021, 02:13 PM   #3
MaryAnn
 
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Default Re: Spaceships: How to take off?

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Originally Posted by Fred Brackin View Post
HEDM is first, Nuclear Thermal Rocket is second and Antimatter Thermal Rocket is third for reason of fuel cost if nothing else. With unlimited budgets you might get a little bettter fuel enconomy with the Ram-Rocket option.

Oh, there was an lmplied bias against Superscience! drives in your post (also one about takign off from Earth) so I assumed you didn't want those. Reactionless Thrusters (above Rotary) are usable if Superscience! is allowed and Contragravity makes lift-off with almost anything possible.
How do they work exactly?

However HEDM is 0.5 mps while the required mps is 5.6 mps for Earth orbit, while Antimatter Thermal Rocket is 0.1G by TL9, 0.2G by TL10, etc. with a delta- V of 1.8 mps, which is lower than the 1G and the 5.6 mps implied to be necessary to take off from Earth...

I guess that I don't get this.
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Old 07-26-2021, 02:19 PM   #4
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Default Re: Spaceships: How to take off?

You need to use multiple engine systems to get the required acceleration and many fuel tanks to get the total delta-v. Consider building a very large multi-stage design.
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Old 07-26-2021, 02:24 PM   #5
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Default Re: Spaceships: How to take off?

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Originally Posted by MaryAnn View Post
How do they work exactly?

However HEDM is 0.5 mps while the required mps is 5.6 mps for Earth orbit, while Antimatter Thermal Rocket is 0.1G by TL9, 0.2G by TL10, etc. with a delta- V of 1.8 mps, which is lower than the 1G and the 5.6 mps implied to be necessary to take off from Earth...

I guess that I don't get this.
You often will have more than one engine (2 HEDM rockets will get you to 1G), and will almost certainly have more than one fuel tank, for liftoff. For HEDM, getting 5.6 mps would call for a little over 12 fuel tank-equivalents - but note that due to the way the rocket equation works, I think somewhere around 4 fuel tanks you functionally get more delta-v per tank than the default, so you'll need markedly less than 12 actual tanks (essentially, so long as fuel isn't a fairly small fraction of vehicle weight, the fact you get lighter as you use it makes it last longer - with 11 fuel tanks, by the time you get to the 11th tank your ship only masses 50% of what it started as). I believe winged designs are also able to reach orbit with less thrust than planetary gravity, by making use of lift (although I think this also tends to burn through a lot more fuel).
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Old 07-26-2021, 02:38 PM   #6
Anthony
 
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Default Re: Spaceships: How to take off?

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Originally Posted by MaryAnn View Post
Most systems have horrendous acceleration in G. In addition, decent acceleration systems have an awful delta-V in mps. What system is the best to take off from Earth without dropping nuclear bombs on the task (Orion Drives)?
There's no options for taking off easily that don't involve low-end WMD, because even the lowest-energy option for getting into orbit (ISp = orbital velocity) generally require somewhat upwards of 20x the payload weight in TNT.
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Old 07-26-2021, 03:17 PM   #7
Emerikol
 
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Default Re: Spaceships: How to take off?

Id go for a g-drive and set it for 1.1 so you can gently glide up into space with no fuss and no muss.
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Old 07-26-2021, 03:29 PM   #8
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Default Re: Spaceships: How to take off?

Realistically, using non-superscience drives, a ship is going to need most of it's mass to be fuel or be the upper-stage of a multi-stage rocket where the lower stage is all fuel and rocket engine. Even the higher TL realistic rockets don't get much better, because gravity wells suck. See the Midnight Sun-Class Orbital Shuttle on p. 7 of Spaceships. The Fuel Tank system on p. 17 explains how you get extra Delta-V (mps) when you have many Fuel Tank systems; this is the "Rocket Equation" bump that was mentioned above.

If you want to have spaceships routinely landing on and taking off from planets you basically need some form of Superscience drive - either straight Reactionless drives or otherwise standard drives with Superscience level of thrust of fuel economy.
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Old 07-26-2021, 04:04 PM   #9
dcarson
 
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Default Re: Spaceships: How to take off?

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Originally Posted by ericbsmith View Post

If you want to have spaceships routinely landing on and taking off from planets you basically need some form of Superscience drive - either straight Reactionless drives or otherwise standard drives with Superscience level of thrust of fuel economy.
Or a ground based launch system like a mass driver, Lofstrom loop, laser launch or such.
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Old 07-26-2021, 07:06 PM   #10
Michael Thayne
 
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Default Re: Spaceships: How to take off?

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Originally Posted by MaryAnn View Post
How do they work exactly?

However HEDM is 0.5 mps while the required mps is 5.6 mps for Earth orbit, while Antimatter Thermal Rocket is 0.1G by TL9, 0.2G by TL10, etc. with a delta- V of 1.8 mps, which is lower than the 1G and the 5.6 mps implied to be necessary to take off from Earth...

I guess that I don't get this.
Antimatter thermal might make sense for an aerospace fighter but they're not very cost-effective for routine passengers and cargo.

Quote:
Originally Posted by Varyon View Post
You often will have more than one engine (2 HEDM rockets will get you to 1G), and will almost certainly have more than one fuel tank, for liftoff. For HEDM, getting 5.6 mps would call for a little over 12 fuel tank-equivalents - but note that due to the way the rocket equation works, I think somewhere around 4 fuel tanks you functionally get more delta-v per tank than the default, so you'll need markedly less than 12 actual tanks (essentially, so long as fuel isn't a fairly small fraction of vehicle weight, the fact you get lighter as you use it makes it last longer - with 11 fuel tanks, by the time you get to the 11th tank your ship only masses 50% of what it started as). I believe winged designs are also able to reach orbit with less thrust than planetary gravity, by making use of lift (although I think this also tends to burn through a lot more fuel).
HEDM engines are 2G each, so it only takes one.
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