Space Exploration & Propulsion Technology

Discussions related to engineering and its applications. From civil and mechanical to aeronautic and robotics, etc.

Re: Spacecraft Propulsion Technology

Postby Darby on July 27th, 2015, 10:08 pm 

CRS-7 Loss Investigation Update ... looks like a faulty strut in stage 2. ... ion-update

Re: Spacecraft Propulsion Technology

Postby Darby on August 5th, 2015, 5:05 pm 

Another installment on the subject of advances in radiation shielding:

A superconducting shield for astronauts

Sounds promising ... I'm looking forward to hearing some data regarding weight, power requirements, and resulting EM shielding.

Re: Spacecraft Propulsion Technology

Postby Marshall on August 5th, 2015, 5:43 pm 

It does sound like a hopeful development; magnesium diboride MgB2
light elements, superconducting up to 25 K, already used in a major application,
they say the magnet would be wrapped in MgB2 "tape", rather than wire. I wonder what the idea of the tape format is. ... astronauts

Maybe wire is what you make out of DUCTILE materials that you can stretch and draw through a succession of dies and this material does not lend itself to making wire---so they make sheets of it and cut the sheets into strips. Or something.

I followed one of the links and got this 2013 wide-audience presentation of the whole menu of bodily problems associated with long missions. FWIW:

Re: Current Affairs

Postby Faradave on August 6th, 2015, 12:20 pm 

Magnetic shielding should deflect electrically-charged cosmic ray particles. But do we really need heavy, energy hungry superconducting magnets? (Today's superconductors must be kept cold and have limited current carrying capacity per cross-sectional area.)

While I'm certain that there's plenty of data on the cosmic ray exposure of astronauts in an orbiting environment, I think this should be re-examined.

If the vehicle's hull (or safe room) is metallic, it should be relatively easy and efficient (weight & energy) to maintain a large static electric charge on it. (Even insulators can sustain charge but charge distribution is different) A moving charge constitutes a current with attendant magnetic field. So, if astronauts are moving in a can holding an electric charge, there would be a magnetic field.

Granted the vehicle probably wouldn't be moving as fast as electrons in a wire but I don't think that's the speed that matters. It would be the relative motion of cosmic ray particles to the static charge that would make them see a magnetic field. The faster the cosmic particles travel toward the vehicle, the more dangerous they are but the stronger the magnetic field they would see.

So, if it hasn't already been done, I recommend putting some radiation detectors in an orbiting, electrically charged, container and re-collecting safety data.
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Re: Space Exploration & Propulsion Technology

Postby Darby on August 7th, 2015, 6:59 pm 

MODERATOR: Can we re-title this thread to "Space Exploration & Propulsion Technology" ?


First space grown food ready for harvest


Re: Space Exploration & Propulsion Technology

Postby BurtJordaan on August 8th, 2015, 1:00 am 

Admin can possibly do that, but it may require creating a new topic with the new Title and then merging this one into it.
I will pm admin.

PS: have done it for 1st post and the last 2; rest still the same.
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Re: Space Exploration & Propulsion Technology

Postby Darby on August 18th, 2015, 9:44 am 

OK, today's Space Exploration technology diatribe concerns flawed Space Elevator models.

Prerequisite Background reading for n00bs: Space Elevators

So, I was just reading this article on Space dot com, and I was immediately struck by a seemingly unavoidable design problem that seems to have avoided the attention of all involved. {ASIDE: It never ceases to amaze me how people will simply throw #$% at a wall, just to see what sticks, gets patented and attracts funding and/or publication}.

In this case, the issue is transverse air-drag induced tension. With a cable design, air drag induced tension is somewhat minimized and as a result the chief loading on the overall system largely devolves to self-mass plus centripital force of orbital speeds, plus cargo load requirements {plus a TBD safety margin} ... still beyond our current abilities, but at least it doesn't include easily avoidable additional loading. However, for a large diameter inflated elevator design like the one in the article, you're adding a VERY LARGE aerodynamic drag factor, which would impact not only positional stability at the distal end, but also cause large increases in the tension loading for the entire length. Just take the classic bird on a tension wire problem, scale up the length of the wire to space elevator lengths, and replace the bird's weight with the aerodynamic drag of a large cylinder of the same height, compute the resulting tension increase over that of a solid cable, and you'll see why I'm giving this one a Bronx Cheer.

Bottom line: do I believe in the Space Elevator concept ? Yes, but we're not quite there yet. However, if one ever gets done anytime soon, it will almost certainly have to be {initially} a cable-ascending technology, not a hollow inflated elevator. Someday yes on the latter, but not soon.

Re: Space Exploration & Propulsion Technology

Postby Darby on September 17th, 2015, 11:50 pm 

Firefly Space Systems of Texas recently tested a new low-power booster using LOx/Methane for delivering smaller payloads (under 400kg) to LEO.


Comment: I was expecting a blue-er flame than the one shown. Perhaps the flow rate of LOx needed tweaking.


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