Talk-Polywell.org

Skipjack wrote:

happyjack27 wrote: And I have math.

And I showed you my math earlier. A very conservatively estimated 20 tonnes to LEO with plenty of margins to go in a LV with minimal refurbishment (and therefore very high flight rate and low operating cost) and a launch cost of less than 2.4 million.
This is as close to airliner like operations as it will get.

well then we must have broken mathematics. we found an inconsistency!

happyjack27 wrote:

Skipjack wrote:

happyjack27 wrote: And I have math.

And I showed you my math earlier. A very conservatively estimated 20 tonnes to LEO with plenty of margins to go in a LV with minimal refurbishment (and therefore very high flight rate and low operating cost) and a launch cost of less than 2.4 million.
This is as close to airliner like operations as it will get.

well then we must have broken mathematics. we found an inconsistency!

What inconsistency?

Skipjack wrote:

happyjack27 wrote:

Skipjack wrote: And I showed you my math earlier. A very conservatively estimated 20 tonnes to LEO with plenty of margins to go in a LV with minimal refurbishment (and therefore very high flight rate and low operating cost) and a launch cost of less than 2.4 million.
This is as close to airliner like operations as it will get.

well then we must have broken mathematics. we found an inconsistency!

What inconsistency?

Exactly.

And for the mth impaired

http://www.nasa.gov/mission_pages/stati ... yanny.html

All about why it cost so much treasure to get to orbit.

In the 1970’s, an experimental nuclear thermal rocket engine gave an energy equivalent of 8.3 km/s. This engine used a nuclear reactor as the source of energy and hydrogen as the propellant.

Hello Dr. Bussard!

Just point ing out that we know how, however, we don't have the stomach to do it that way. Or even boost them chemically to space, and then run them for solar system access...

Meh...

A nuclear rocket if properly optimized could get into orbit safely. The big problem is that a "safe" ntr barely has the isp and raw thrust. The higher thrust and isp rockets get hot enough the core degrades, leaving fallout in the exhaust stream.

Some of the combined ideas with "afterburning" hydrogen with oxygen or air can get better, and a technically practical design was considered possible, but no political will for anything nuclear.

SpaceX is planning a Dec 16 launch from Vandenberg AFB, assuming they get FAA approval. Looks like they may have figured out what happened back in September.

From the article I was reading on Universetoday.com, the problem on Sept 1st was oxygen solidifying next to/on the carbon-fiber He tank while the He was being loaded (the He tank is inside the LOX tank).

Through extensive testing in Texas, SpaceX has shown that it can re-create a COPV failure entirely through helium loading conditions,” SpaceX said. “These conditions are mainly affected by the temperature and pressure of the helium being loaded.” You would have thinked they would have tested more before this point.

paperburn1 wrote:Through extensive testing in Texas, SpaceX has shown that it can re-create a COPV failure entirely through helium loading conditions,” SpaceX said. “These conditions are mainly affected by the temperature and pressure of the helium being loaded.” You would have thinked they would have tested more before this point.

Tested more what? They've loaded such tanks under fueling conditions several hundred times now before the accident.

Well I'm really not sure if that's 100% true. If they found a way to repeatedly replicate the event then there must've been something in their testing that prevented them from finding it in the first place. To be able to duplicate everything would be extremely hard and they are moving at a pace that could be easily considered 10 times faster than any NASA developments that have occurred. But in the final analysis "space is hard" and at least now they know where the problem lies lies so they can get past that point and on launching more rockets.

And they found a reason for the event that was NOT sabotage. That is good ...

paperburn1 wrote:Well I'm really not sure if that's 100% true. If they found a way to repeatedly replicate the event then there must've been something in their testing that prevented them from finding it in the first place.

A good comparison could be the square windows issue used in the first commercial jet airplane, the Comet.
It was not until one year from entering into service that the first Comet planes started exploding for "unknown" causes at high altitude. It took several month of tests on a Comet fuselage to discover that the issues was caused by the shape of the windows.
Once you realize where the issue was it is easy to replicate it and to understand why you missed it with the previous test procedures.
Time and experience solve everything.

My (limited) understanding of the problem is that it only became an issue with their recent switch to "super" cooled LOX. At "normal" LOX temperatures, which all of their launches prior to this year used, the problem does not occur.

Looks like both SpaceX and I were a bit optimistic about their return to flight status. From this article:

However, the launch date was pending until approval by the FAA – which will not yet be forthcoming in time to meet the Dec. 16 target date.

The FAA can’t approve a launch until they have a report to review from SpaceX. And that final accident investigation report has not yet been written by SpaceX or submitted to the FAA.

In a new update, SpaceX announced that they “are finalizing the investigation into our September 1 anomaly” and need to “complete extended testing” – thus inevitably delaying the hoped for blastoff into early January 2017.

Bummer. However, also understandable.

It is not only the super chilled liquid oxygen, but changing/ evolving oxidizer and gaseous helium loading procedures that evidently pushed them over the edge. The procedures were changing in order to better manage launch window opportunities with the temporary superchilled liquid oxygen storage lifetime. From Spaxe X reddit forum- Compressing gaseous helium leads to some weird results, even cooling (while with most gasses compressing causes heating). As the liquid oxygen was superchilled- meaning it was closer to its melting point, the cooling of the helium tanks as they were filled could , and presumably did, chill the liquid oxygen locally to the point that it solidified. I'm guessing that solid oxygen may expand like water ice does compared to it's liquid density. This led to separation of the carbon wrapped layers, loss of the considerable strength necessary to contain the high pressure gaseous helium with subsequent rupture of the tank.

As I understand it, this is why SpaceX has hinted that it was a procedural error and not a structural or design flaw. They basically filled the helium tanks too fast, a condition easy to replicate with subsequent tests. Either filling the helium tanks slower and/or chilling the liquid oxygen a little less are procedural changes that may easily eliminate the unanticipated problem.

Dan Tibbets