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RobertDyck

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From: Winnipeg, Canada

Registered: 2002-08-20

Posts: 7,935

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Re: Columbia Loss Adds More Support to Hypothesis

In the late 1980's an engineering study updated the Nerva design from the 1960's NTR engine. The Nerva 2 engine completed in 1974 had an Isp of 825 seconds, and a thrust in vacuum of 88,451kg force so it is very similar to the Timberwind-75. However, Nerva massed 11,860kg instead of 2,500kg for Timberwind. The updated version of Nerva increased the Isp to 925 seconds in vacuum, and a thrust of 34,000kg force (half that of Timberwind-75) but still had a mass of 8,500kg. Nerva is just heavy.

The advantage of Nerva is that it encapsulates every piece of uranium in a ceramic capsule so strong it could fall out of orbit and not crack on impact with the ground. I the case of a catastrophic failure, the rocket would fragment but the pieces could be picked up by workers in radiation suits using Bar-B-Q tongs and lead boxes (you want to keep the pieces separate). Nerva might not be the most efficient, but it's safe and clean. You could argue that operating a NTR engine as a launch vehicle leaves radioactive fuel modules laying all over the debris field after a catastrophe, but I think the weight of pieces of rocket falling is more dangerous, and the hydrazine and nitrogen tetraoxide of the Shuttle's RCS thrusters is chemically poisonous, so it's just as dangerous.

Just how safe or clean is Timberwind? I don't know. Both engines use uranium. You don't want to use plutonium, it's chemically extremely poisonous. Timberwind was a pebble bed fast reactor; I think it used enriched uranium: 10% U-235. That reduced the "dead weight" of U-238 it carried. A fast reactor would only carry enough U-235 for its launch. It would have to be refuelled for a second launch. Also, Timberwind was designed for expendable rockets, so I doubt it was designed to be refuelled or re-used. With any nuclear reactor you have to worry about the high radiation in the core converting material of the chamber, pipes, etc, into another element. That causes high rates of wear.

Could a smaller launch vehicle use 3 Timberwind-45 engines with tanks and body the size of X-33 and still carry the same cargo load as Shuttle to the ISS? Maybe. Upon landing you would have to stay away from the rear end of the spacecraft until radiation hardened robots removed the spent nuclear material. I'll try to calculate the LH2 mass and volume, and the performance for this version. One thing to worry about is that nuclear engines are heavy so it could unbalance the craft when flying during re-entry.

I think we should move this discussion to "Interplanetary transportation".

Palomar

Member

From: USA

Registered: 2002-05-30

Posts: 9,734

Re: Columbia Loss Adds More Support to Hypothesis

Asteroids Named for Columbia Astronauts

*And I think that's a wonderful idea.

--Cindy

*Last evening my husband and I happened to drive past a new high school, recently built and soon to open.  I happened to notice the sign on the school's lawn:  The school's name is "Columbia," and their team name is "Explorers."  This piqued my interest, of course...and as we drove directly past the sign I looked more closely:  On the sign is the outline of the space shuttle Columbia, and to the right of it the outline of an astronaut spacewalking, complete with tether. 

Cool, huh?    A high school named in honor and memory of the Columbia tragedy and her crew.

--Cindy

---

We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

Surferosad

Member

From: Montreal, Canada

Registered: 2003-08-28

Posts: 16

Re: Columbia Loss Adds More Support to Hypothesis

It seems to me that there's quite a lot of people arguing, directly or indirectly, for one of the latest US presidential follies i. e. militarisation of space, simply because they hope this will provide the incentive (and the technology) for space exploration.    This line of reasoning is, I think, a mistake: anything that might increase the chances for a devastating war in the near (or not so near) future must be actively fought!  I'm in as much of a hurry as anyone else here to see humanity stepping on the Martian surface, but first we have to keep from blowing ourselves up!  Putting weapons in Earth orbit increases the chance of sending us back into the stone age !  I guess that would be a big blow for Mars colonization, right?

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,433

Re: Columbia Loss Adds More Support to Hypothesis

It's been such a long time, but an anniversary of the ship's loss is about to occur.

NASA remembers fallen astronauts as 20th anniversary of Columbia disaster nears On Feb. 1, 2003, the Space Shuttle Columbia exploded while returning to Earth.

tahanson43206

Moderator

Registered: 2018-04-27

Posts: 19,421

Re: Columbia Loss Adds More Support to Hypothesis

For SpaceNut re #29

Thanks for this reminder of the tragic day!

While it will be difficult to look back, your reminder helps to prepare for the media presentations we'll be seeing shortly.

(th)