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#1 2024-07-07 12:38:53

kbd512
Administrator
Registered: 2015-01-02
Posts: 7,612

Why Economics Favors Mass Drivers Over Heavy Lift Rockets

In the following YouTube video, we have a pretty good economics-based explanation for why we need something like gun launchers, electromagnetic mass drivers, or centripetal acceleration launchers to reduce the cost of missions to other planets:

Why Physics Favors a Mass Driver Over Heavy Lift Rockets

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#2 2024-07-07 13:35:16

tahanson43206
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Registered: 2018-04-27
Posts: 18,189

Re: Why Economics Favors Mass Drivers Over Heavy Lift Rockets

This post is reserved for an index to posts that may be contributed by NewMars members over time.

Best wishes for success with this promising new topic.

The video is from the 2024 (May) ISDC.  It shows a launcher almost identical to a concept that kbd512 described in some detail earlier in the forum archive.

(th)

Last edited by tahanson43206 (2024-07-07 13:45:04)

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#3 2024-07-08 14:32:55

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,620
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Re: Why Economics Favors Mass Drivers Over Heavy Lift Rockets

The physics is favorable,  but there is a cost:  extreme launch gees.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#4 2024-07-09 12:40:51

JoshNH4H
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From: Pullman, WA
Registered: 2007-07-15
Posts: 2,559
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Re: Why Economics Favors Mass Drivers Over Heavy Lift Rockets

SSTO is a funny problem.  On a very slightly smaller planet (for example, if Earth were as big as Venus), it would likely be the optimal solution for launch.  As things stand, our planet is just slightly too big: Available chemical exhaust velocity is too low to enable lower mass ratios, and available materials are too weak and heavy to withstand the high mass ratios needed.

The problem is such that a relatively small boost of 500 m/s (~1100mph), if it came with no other downsides, would be enough.  This is why you see a reasonably high number of 1.5 stage vehicles, like the space shuttle.  It's why SpaceX's partially reusable concept (F9) still employs a pretty low staging velocity, and it's why airlaunch is a perpetually attractive option (even though nobody has yet built a SSTO H2/LOX airlaunch, taking advantage both of the plane's speed around 320 m/s and the fact that a separation in the stratosphere allows you to use a regular ~vacuum-optimized engine.

The benefits to a stationary device that gives you even this much are undeniable.  Unfortunately, the drawbacks--harsh tradeoffs between very high up-front capital costs, separation speeds, and high gee-loading--mean that it's hard to imagine an actual device that does what we'd want it to do.  The gee-loading from chemical launch is already a significant constraint on crewed launch and satellite design alike.

One way to avoid this is to have a trackless track: We're back at airlaunch, or a first stage, basically. Maybe a long enough track pays off once payload volumes are really high.


-Josh

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#5 2024-07-09 18:36:16

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 29,314

Re: Why Economics Favors Mass Drivers Over Heavy Lift Rockets

For the moon one can modify the moon as the structure for Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Massspinlaunch-marker-hg.jpg will not be needed. Surely we can send heavy mass from the moon.

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#6 2024-07-10 10:03:41

JoshNH4H
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From: Pullman, WA
Registered: 2007-07-15
Posts: 2,559
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Re: Why Economics Favors Mass Drivers Over Heavy Lift Rockets

ymmv but the engineers I know mostly regard spinlaunch as a joke


-Josh

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#7 2024-07-10 12:39:54

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 3,584

Re: Why Economics Favors Mass Drivers Over Heavy Lift Rockets

What does spin launch provide that a linear accelerator (coil gun) does not?  Mechanical forces in spin launch will be extreme.


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#8 2024-07-10 15:13:57

tahanson43206
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Registered: 2018-04-27
Posts: 18,189

Re: Why Economics Favors Mass Drivers Over Heavy Lift Rockets

For Calliban re #7

The difference is in performance.  The SpinLaunch folks have already achieved more than humans trying linear launch have achieved since the beginning of time.  The US military has achieved the ability to launch a fighter aircraft from a carrier, and that is an impressive feat, but all the talk of launches to LEO are just hot air.

I have reported on Dr. John Hunter's efforts to build a LEO gas gun, but he has not secured the funding to proceed. I am reasonably confident he could deliver a system, but it would be big, and it would be expensive, and my guess is that potential funders are not available.  Dr. Hunter achieved comparable performance while researching for Star Wars at the University of California.  All this is documented in the forum archive.

Bottom line... the linear folks are full of great vision but essentially zero performance, aside from the US Navy fighter launcher.

Here is a YouTube video from 14 years ago, in which Dr. Hunter describes the system he would like to build. https://www.youtube.com/watch?v=s7RGSBOmsm4

(th)

Last edited by tahanson43206 (2024-07-10 17:24:17)

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#9 2024-07-11 10:01:49

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,620
Website

Re: Why Economics Favors Mass Drivers Over Heavy Lift Rockets

I would only point out that heavy-lift rockets are a technology already-in-use and well-proven.  Neither spin launch,  nor light gas guns,  nor any sort of electromagnetic catapult,  are ready-to-use launch technologies.  All would require considerable development and shakedown to become operational and reliable,  if any of them actually prove feasible for launch at all.   

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#10 2024-07-11 10:28:28

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 18,189

Re: Why Economics Favors Mass Drivers Over Heavy Lift Rockets

For kbd512 ... when you get power back, and assuming the family got through Beryl OK, please add a bit more to this interesting topic.

My observation/expectation is that non-rocket launch systems ** should ** be cost effective, if they work, but as GW points out, none of the fancy gee-whiz linear launch methods have amounted to a hill of beans, with the sole exception of the US Navy fighter catapult, which cannot launch anything  more than a fighter jet .

Rather than pour a lot of effort into theory, please focus your energy on practical achievement anywhere in the world where a serious effort to build a linear launch system might have been undertaken. I think you will find nothing beyond the work of Dr. John Hunter, but you might.

(th)

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