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#201 2021-09-13 08:46:35

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,625
Website

Re: Deep Space Gateway; a bad joke by NASA?

There are two very serious problems with the Gateway station in this odd halo orbit.  One is quite literally fatal to its crew. 

The delta-vee to reach it from Earth is actually a bit lower than the delta-vee to reach a low lunar orbit similar to Apollo,  especially one oriented polar.  That puts Gateway within reach of SLS Block 1 with the (overweight) Orion and (underpowered) service module it has.  SLS-block1/Orion cannot successfully reach the low lunar orbit used by Apollo,  much less a polar-oriented low lunar orbit.

From low lunar orbit,  the theoretical delta-vee required to land is comparable to the low orbit velocity:  about 1.6-something km/s.  Actual is a tad higher due to gravity losses and propellant safety margins.  This is true whether the orbit is equatorial or polar. 

From the halo orbit,  you have a trivial burn of a few m/s at apolune to put you onto a surface-grazing transfer ellipse, BUT,  the perilune velocity is what you have to "kill" to land!  From that orbit,  the perilune velocity is trivially-less than lunar escape velocity:  2.5-something km/s.  That's 41% higher than from low lunar orbit!

That's NOT the fatal problem,  it is just added difficulties designing lunar landers with a lot more mass ratio than they should otherwise need,  all because SLSblock-1/Orion is a faulty moon rocket design,  with enormous sunk costs that NASA is unwilling to write off.  They couldn't write it off,  even if they wanted to,  because Congress,  not NASA,  controls ALL of NASA's money.  Congress has micromanaged NASA for decades,  and they are NOT competent to do so!  They never have been.  It is really starting to show,  too!

The fatal problem is sudden solar flare events of large magnitude.  Not all are lethally large,  but some are.  The Gateway station design does NOT have a radiation shelter for its crew,  but in that (or any) orbit about (or even near) the moon,  it has no effective shielding from Earth's magnetosphere. 

The Apollo data show that typically spacecraft hulls can cut that kind of radiation roughly in half,  but that's not good enough for a big event,  not by a very long shot!  You might be looking at as much as 5-to-10 THOUSAND REM accumulated over 5-10 hours.

This is not galactic cosmic rays I am talking about;  that's a thin drizzle of far higher-energy particles,  difficult to shield.  But there's actually very little of it:  some 24 to 60 REM accumulated over a year.  Supposedly,  accumulating 400 REM over a career in space increases your risk of late-in-life cancer by something like 3%.

300 REM accumulated in a "short time" (hours to days) is lethal to 50% of those exposed,  the other 50% very-nearly dying of severe radiation sickness.  Extremely severe.  500 REM is lethal to 100% of those so exposed.  It is a very,  very ugly death.

There was indeed an event of that magnitude,  between the last two Apollo missions to the moon in 1972.

As it says in the quote beneath my byline,  there is nothing as expensive as a dead crew,  especially one dead because of a bad management decision.  This is a TERRIBLY BAD management decision!  It WILL kill a crew!

GW

Last edited by GW Johnson (2021-09-13 08:56:23)


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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#202 2021-09-13 09:44:34

Oldfart1939
Member
Registered: 2016-11-26
Posts: 2,239

Re: Deep Space Gateway; a bad joke by NASA?

GW-

Here is a repost of my original opener for this thread:

"Ever since NASA announced their latest workfare program for their favored contractors, I've been wondering exactly who came up with this terrible idea. It sounds like a bad medical experiment designed by Josef Mengele for the residents of a concentration camp!

The idea of placing a long-term habitat in cis-lunar space with no provision for shielding from solar flare radiation and GCR, and which makes  no attempts made to alleviate the effects of microgravity, makes me wonder just what they hope to achieve other than killing or seriously injuring the astronauts involved. First proposed by NASA, and now we have the ESA jumping on board the idea along with the Russians. Other than providing something to justify the enormous amount of capital expended on the SLS, it seems to serve no truly useful purpose. It's another NASA let's all get on board and go...nowhere."

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#203 2021-09-13 17:39:07

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 23,403

Re: Deep Space Gateway; a bad joke by NASA?

you could blame that on the prime contractors that used an ISS for a model....

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