Nasa may drop Ares 1-Y flight

[Moonwalker]

Make it a full quote:

For Ares I, engineers expect a smooth ride up from liftoff to 115 seconds, but as the first stage nears burnout, thrust oscillations could pose a problem for a few seconds impairing the crew’s ability to read displays and respond to what they see.

Not just that the article is contradicting itself - higher vibration thresholds are not smooth, but the opposite, the complete sentence is also not the same as your partial quote.

And also not wrong:

The vibration issues are not related to the complete first stage powered flight. It's related to the very last seconds shortly before separation. The first 115 seconds of the flight are expected to be smooth.

 

[Urwumpe]

Still the article is writing claims, that are not backed up by any technical report or presentation published outside NASA - maybe somebody has found more internal stuff in L2, but I can't find any paper that says the opposite of the earlier calculations and test firings.

Your blog article even refers to the findings of such test firings, as the frequency of the main vibrations, which is also documented in the technical reports. The only difference between technical reports and blog article is actually only the overly optimistic claim of the first 115 seconds being smooth.

The technical reports actually speak of strong vibration amplitudes already at 80 seconds (without aerodynamic vibrations, which cause most of the Space shuttle vibrations).

 

[garyw]

Still the article is writing claims, that are not backed up by any technical report or presentation published outside NASA - maybe somebody has found more internal stuff in L2, but I can't find any paper that says the opposite of the earlier calculations and test firings.

Doing a search for "thrust oscillation" on NSF shows this article which is the latest published item on thrust oscillation and is public -> http://www.nasaspaceflight.com/2008...n-meetings-encouraging-allowance-for-changes/

The latest L2 information on thrust oscillation is from 23rd January 2008 and was relating to a tiger team assembled to tackle the issue.

Disappointingly there is no more information on the issue so I think it's just a matter of waiting and seeing. Certainly Thrust Oscillation is an issue, that's proven because a tiger team was assembled to investigate it but we don't know the current status of any fix so arguing about it will achieve nothing as we don't have up to date facts.

 

[Urwumpe]

It also does only mention how much wrong the test persons read the data, and 10% and 1g is more than it sounds like, just 10% is not the case.

 

[Moonwalker]

As long as there are no up to date facts, I personally tend to trust NASA articels, NASA TV broadcasts and NASA people.

Thrust oscillation certainly is an issue (I've never said the opposite), but not a new one and certainly not a non-fixable one. Otherwise NASA would walk away from it. But if they say that they expect a relatively smooth ride compared to the crews unability to read instruments at burnout, they for sure have a reason to say so. As far as I know they never said that the entire ride on top of the first stage would be something like catastrophic.

Those 115 seconds of a smooth ride is not a news at all (and not a personal stomach feeling or a lie). It had been pointed out by Garry Lyles (associate director of technical management at NASA's Marshall Space Flight Center) already more than a year ago. So I'm wondering that this does get so much attention suddenly.

http://spaceflightnow.com/news/n0808/19ares1/

A newer article:

http://www.spacenews.com/civil/fix-for-ares-vibration-issue.html

 

[Urwumpe]

Just remember: NASA did also not walk away from debris shedding of the ET, until it caused the LOCV of Columbia.

 

[Moonwalker]

Just remember: NASA did also not walk away from debris shedding of the ET, until it caused the LOCV of Columbia.

That's right. But I think it's too early to conclude that Orion crews will be in trouble during first stage ascent. They're still working on the entire LV and looking forward to fix that issue.

 

[Urwumpe]

That's right. But I think it's too early to conclude that Orion crews will be in trouble during first stage ascent. They're still working on the entire LV and looking forward to fix that issue.

My personal opinion is, that they pretend activity. The NASA budget is too small anyway for what is demanded, and the work on the LV is mostly about fixing problems, that wouldn't exist if Ares had a proper initial design process, like NASA likes to teach students, but which NASA does not follow.

 

[Moonwalker]

I think the problem is that NASA did not get the budget it was promised. They actually try to do what the former government said they should do, but by less budget. That's the biggest challenge in my point fo view. The Shuttle retirement might offer some more money but still not enough to return to the Moon.

A launch vehicle, Ares I or not, will lift Orion into orbit sooner or later anyway I think. But the future regarding the Moon is still quite uncertain (not to mention Mars). Obama has to take difficult decicions. But he has to take them and he and the congress shouldn't wait for too long. I personally don't really like the possibility of witnessing the ISS in orbit until 2020, while Orion just doing nothing more than ferry flights. Even worse if there would be a replacement of the ISS in the 2020s and "nothing else" taking place. But of course that's just my opinion.

For now, to cancel Ares I-Y is not too bad I think. Depending on the decissions of Obama and the congress, that cancelation potentially offers more advanced test flights in future I think.

 

[Unstung]

I wish the damn government would give NASA more budget (double it), living on the moon would be a tremendous accomplishment, seems to be worth more than plenty the government is paying for right now. But the cancellation of the Ares I-Y doesn't seem to be a big blow as long as NASA fully tests the Ares with everything before the first manned flight (Ares I-X Prime?).

 

[n72.75]

I wish the damn government would give NASA more budget (double it), living on the moon would be a tremendous accomplishment, seems to be worth more than plenty the government is paying for right now. But the cancellation of the Ares I-Y doesn't seem to be a big blow as long as NASA fully tests the Ares with everything before the first manned flight (Ares I-X Prime?).

Sadly, the government(s?) doesn't take spaceflight searously though.

 

[martins]

Article somewhat related to this thread:

http://www.huffingtonpost.com/buzz-aldrin/why-we-need-better-rocket_b_351335.html

 

[SiberianTiger]

"Bypass a foolish Moon race!"

!

 

[Urwumpe]

Article somewhat related to this thread:

http://www.huffingtonpost.com/buzz-aldrin/why-we-need-better-rocket_b_351335.html

:thumbup:

*reads the Ares I-X discussion again*

 

[agentgonzo]

What causes the thrust oscillations in the SRB that fires ares? I know that in liquid rockets you get the acceleration causing the flowrate through the turbopumps to vary causing variation in the thrust and feeds back. But in a solid rocket this feedback won't be there as there are no turbopumps to put the fuel into the rocket as it's already there. It is the back pressure from the solid rocket exhaust?

 

[Urwumpe]

it is called "vortex shedding" - turbulences that form inside the combustion chamber by small pressure waves.

http://en.wikipedia.org/wiki/Vortex_shedding
http://www.fluent.com/about/news/newsletters/05v14i3/s7.htm

Also, you will get the same feedback in SRMs, since the pressure has (usually negative) effect on the combustion rate and the produced thrust.

 

[garyw]

Isn't there also a problem where the burn rate of solid fuel is variable? Not by much but by enough to give additional vibration due to the uneven burn rate.

It's one reason that both SRB's are filled from the same propellant casting and also the reason that satellites/probes which use a solid escape/boost stage use spin stablisation

 

[Andy44]

Right on, Buzz!

 

[mjessick]

Or, if you are going to do a two element launch for a beyond low Earth orbit mission (incidentally leaving the middle cargo zone for commercial explotation), then maybe, just maybe, you want something for the second launch that has a chance of launching on time.

 

[SiberianTiger]

Or, if you are going to do a two element launch for a beyond low Earth orbit mission (incidentally leaving the middle cargo zone for commercial explotation), then maybe, just maybe, you want something for the second launch that has a chance of launching on time.

One cool solution for that problem is to launch the part that can wait in orbit, first and launch the less "patient" element second for the subsequent rendez-vous. Example: launch a tin can with people of board first; let it dock to a space station to make them reasonably luxurious conditions while they are standing by; launch the tug+lander stack second and rendez-vous it with the crew carrier in vicinity of the station; then perform TLI before LH2 fumes out.