5.5 Segment Ares I

[guru]

So, NASA is considering switching the CaLV booster to use a 5.5 segment motor.  Does this mean that they have to go back and redesign Ares I, since most of the justification for it is to create components for the CaLV (Ares VI)?

[hyper_snyper]

How long will the gap be with a 5.5seg? 

[guru]

How long will the gap be with a 5.5seg? 

Forever and ever, worlds without end. j/k I think.

My guess is that the gap will be longer by at least a year and a half, since they've already built and test fired a couple of those, and thus already have the tooling and grain design in place.  If they think flight oscillation is bad with five segments, though, wait until you fly with six.

(By the way, what is it with all of the "and a half" s.  e.g. one and a half launch architecture, five and a half segments.)

[guru]

By "a couple of those" I mean "a couple of the five segment boosters".

[Thorny]

If memory serves, a "segment" is made up of two "drums" loaded with propellant and connected at the factory (a "factory joint"). Then the segments are connected "in the field" at the launch site (the "field joint").

The Five Segment SRB previously planned had one more segment (two drums) than the Shuttle SRBs.

The new lengthened SRB gains one more drum, not two, so it is only gaining half a segment, i.e., 5 1/2 segments.

[Patchouli]

Wouldn't it be easier to just switch the the Jupiter 120 then mess with a 5.5 segment srb since even the five segment srb is trouble?
Other options why not use some small strap on srbs to get extra performance like JAXA does on the H2A?
If they added four GEM60s they might even be able to get away with just a four segment RSRM.
Yes I know this makes five srb start events vs one but if you ask me it's probably a lot safer then working the bugs out on what turns out to be a completely new SRB design with new nozzles,a new fuel grain,and new recovery systems etc.
Other solutions maybe use four of the H2A boosters on Ares V plus the two RSRMs.

But the best solution would is that provided by the direct launcher group as both vehicles only have two SRB start events and RSRM remains unchanged from the shuttle.
The J-120 CLV also has no air start events so I think it would be safer then Ares I.

[marsavian]

The J-120 would be easier but it's not safer. 2 SRBs, a big fuel tank and 2 RS-68s all in parallel is not a safer configuration than a J2-X on top of a SRB both intuitively and by the calculated numbers.

[Tim S]

So, NASA is considering switching the CaLV booster to use a 5.5 segment motor.  Does this mean that they have to go back and redesign Ares I, since most of the justification for it is to create components for the CaLV (Ares VI)?

Ares I remains a five segment first stage solid. The 5.5 is for Ares V, and may be six segments, but Ares I remains unchanged. There's a long way o go until anything happens with Ares V, so Ares I will continue unhindered.

This is the correct move as additional changes to Ares I's first stage at this time may delay us past the 2016 first flight to the ISS, which is not desirable.

[TrueBlueWitt]

So, NASA is considering switching the CaLV booster to use a 5.5 segment motor.  Does this mean that they have to go back and redesign Ares I, since most of the justification for it is to create components for the CaLV (Ares VI)?

Ares I remains a five segment first stage solid. The 5.5 is for Ares V, and may be six segments, but Ares I remains unchanged. There's a long way o go until anything happens with Ares V, so Ares I will continue unhindered.

This is the correct move as additional changes to Ares I's first stage at this time may delay us past the 2016 first flight to the ISS, which is not desirable.

Why have a program where you have to wait till 2016 in the first place?  How strict are the weather launch limits going to be on Ares-I with "sail" effect? Won't this increase potential LOM when trying to launch to meet up with a short shelf life EDS launched on the Ares V monstrosity?

Doesn't the new height of AresV now almost preclude ever man rating it as there won't be clearance for the LAS?

How does building two brand new non-shuttle derived rockets make economic sense?

If you are starting from "Scratch" at least come up with an "optimized" solution(Direct or otherwise), not putting band-aids on top of band-aids, that still don't give you a system that meets your exploration requirements.

[gladiator1332]

So, NASA is considering switching the CaLV booster to use a 5.5 segment motor.  Does this mean that they have to go back and redesign Ares I, since most of the justification for it is to create components for the CaLV (Ares VI)?

Ares I remains a five segment first stage solid. The 5.5 is for Ares V, and may be six segments, but Ares I remains unchanged. There's a long way o go until anything happens with Ares V, so Ares I will continue unhindered.

This is the correct move as additional changes to Ares I's first stage at this time may delay us past the 2016 first flight to the ISS, which is not desirable.

Taking a "we'll worry about it when we get there" policy with Ares V is just setting this thing up for failure. We are now building two completely new and different vehicles that have little in common.

One of the strongest arguments Griffin has made for Ares I is that the 5 seg is needed for Ares V...now this commonality is out the window. That argument has been blown out of the water by changing to the 5.5 seg for Ares V.

[Jim]

This is the correct move as additional changes to Ares I's first stage at this time may delay us past the 2016 first flight to the ISS, which is not desirable.

It will do that on its own without any help

[Antares]

"Worry about it when we get there": that's the story of ESAS funding, ladies and gents.

[madscientist197]

This is pretty much the worst possible outcome possible from the VSE. If China actually has lunar ambitions, they must be laughing.

Why is it that NASA can't budget properly? This is my biggest concern - why have they systematically underestimated costs/mass requirements?

IMHO they need to start cutting back on features to save the lunar program. I would start by giving up on anytime return, I also suspect a methane/oxygen ascent stage would be somewhat cheaper than the 5.5 segment/core stretch/extra engine changes (not that I know the precise tradeoffs).

[Danny Dot]

This is pretty much the worst possible outcome possible from the VSE. If China actually has lunar ambitions, they must be laughing.

Why is it that NASA can't budget properly? This is my biggest concern - why have they systematically underestimated costs/mass requirements?

I think "Vanilla" summed it up well in a different thread.  The conceptual design of NASA vehicles is not being done by conceptual design teams.  It is being done by politically motivated managers.

[Namechange User]

This is pretty much the worst possible outcome possible from the VSE. If China actually has lunar ambitions, they must be laughing.

Why is it that NASA can't budget properly? This is my biggest concern - why have they systematically underestimated costs/mass requirements?

IMHO they need to start cutting back on features to save the lunar program. I would start by giving up on anytime return.

This is a little unfair.  What we have here is not underestimating costs, but major engineering issues that are driving changes and the cost way beyond the original estimate or orginal architecture proposal.  Essentially we are now in apples and organges mode when it comes to the the ESAS pick and what is in development. 

It is very hard to estimate cost when you are willing to do anything to have your pet architecture fly, regardless of the effect on other elements or to schedule and budget.

[madscientist197]

This is a little unfair.  What we have here is not underestimating costs, but major engineering issues that are driving changes and the cost way beyond the original estimate or orginal architecture proposal.  Essentially we are now in apples and organges mode when it comes to the the ESAS pick and what is in development. 

You're right, the same thing happens in software engineering. Tons of projects go overbudget/late and it's impossible to see what all the problems will be down the line that may affect cost/schedule etc. It doesn't make me feel any better though, and for-better-or-worse it is very easy to blame NASA.

If I was in their position, I probably wouldn't have done any better - but it is frustrating.

[Namechange User]

So, NASA is considering switching the CaLV booster to use a 5.5 segment motor.  Does this mean that they have to go back and redesign Ares I, since most of the justification for it is to create components for the CaLV (Ares VI)?

Ares I remains a five segment first stage solid. The 5.5 is for Ares V, and may be six segments, but Ares I remains unchanged. There's a long way o go until anything happens with Ares V, so Ares I will continue unhindered.

This is the correct move as additional changes to Ares I's first stage at this time may delay us past the 2016 first flight to the ISS, which is not desirable.

I agree this is exactly what will happen and have said this in the Ares V hot topic thread.

I'm curious as someone who works at MSFC, what your opinion is on this.  I have no idea who you are but do you personally think this is the best use of our limited budget given the new development costs that will be added to Ares V and then the increased sustaining/operating costs that will each project will have to absorb if Ares I does not change? 

Do you belive that it is worth the cost to develop/qual Ares I to a 5.5 segment later after all that will have been spent on this version?

[Patchouli]

The J-120 would be easier but it's not safer. 2 SRBs, a big fuel tank and 2 RS-68s all in parallel is not a safer configuration than a J2-X on top of a SRB both intuitively and by the calculated numbers.

Actually the J-120 would be much safer as it has better mass margins and the four segment RSRM is well understood.
Also having better payload margins means the Orion can keep it's redundant systems.
I seen too many instances where a redundant system saved a shuttle mission and a failure was just an annoyance vs a life threating situation.
A good example of this is when one of the pumps in the shuttle's coolant loop system failed and they still had a second backup with the flash evaporator.
Lastly the abort options are a lot better with the J120 and a lot less likely to be used since the RS-68s are ground started the vehicle doesn't leave the pad until it's known the main engines are healthy.

Most rocket engine failures happen in the first few seconds of operation hard starts,FOD or turbo pump failures etc.

Ares I if the second stage fails to start guess where you come down in the middle of the Atlantic not a desirable option.

If you ask me Ares I has turned out to be a death trap it needs active damping just to not kill anyone riding it that doesn't sound very safe to me.

I question those who calculate the safety on concepts and their ability or at the very least honesty.
 I also wonder where they get their numbers but I think we can safely say those numbers are not worth the paper they are printed on.

It seems they don't know of things that have been developed since 1967 such as vehicle health monitoring and Kevlar shields which would allow one to escape the stack long before it's in the process of exploding.

BTW on the reliability of vehicle health monitoring and computer controls if you ever fly on an airliner or ride a train your life is depending on the reliability of such systems.

[Jim]

Ares I if the second stage fails to start guess where you come down in the middle of the Atlantic not a desirable option.

No, just 150 mi or so offshore just like the SRB's

[MrTim]

Actually the J-120 would be much safer as it has better mass margins and the four segment RSRM is well understood.
Also having better payload margins means the Orion can keep it's redundant systems.
I seen too many instances where a redundant system saved a shuttle mission and a failure was just an annoyance vs a life threating situation.
A good example of this is when one of the pumps in the shuttle's coolant loop system failed and they still had a second backup with the flash evaporator.
Lastly the abort options are a lot better with the J120 and a lot less likely to be used since the RS-68s are ground started the vehicle doesn't leave the pad until it's known the main engines are healthy.(snip)

Yet another thread gets swallowed-up by Direct advocacy (sigh)
1. Mass margins are not everything, and if Ares I/Orion (which is what we are getting) ends-up with low margins, they'll simply cut down on what they crew can take with them rather than leaving the redundant safety options on the pad. NOBODY will say "Here, Guenter, hold this backup computer, I'm taking a cake, a buzz lightyear toy and another change of clothes instead!" as he climbs aboard a capsule. Obviously, those decisions will happen well-before launch day, but some people seem to not understand that all flying vehicles experience trade-offs early in their designs; they rarely make it to first flight with all the options and capabilities initially proposed...and there's nothing wrong with that.
2. Just what are the abort options when one of your precious J-120 SRBs ignites and the other one does not? (I know, no SRB has ever failed to start, but it is possible and has always been a danger with STS. No SRB had ever burned-through on STS before Challenger. "Never happened before" is not proof it will never happen, or proof it will not happen on the very next launch attempt.)
3. Air-starting the second stage is indeed a LOM risk, but that is a risk the US program has accepted in Gemini and Apollo. With Ares I, the basic rocket is so cheap that if the upper stage is lost (and assuming they keep the 1st stage and the capsule re-usable) you may really only lose the consumables, abort system, and the upper stage; you do not even lose the cargo, since it's either in the capsule with the crew or on another rocket. You could even have a second Ares I stacked in the VAB and a backup crew ready to go so an overall "mission" to the moon or Mars would not be lost. ( It makes more sense to me to not launch one Ares I until the next one is stacked and ready. After the 1st pair are stacked, you stack the same number per year, but you gain options for things like a rescue mission. After each launch, the backup become the next primary, and you start stacking the next backup. )

If you ask me Ares I has turned out to be a death trap it needs active damping just to not kill anyone riding it that doesn't sound very safe to me.

"death trap" is way too far. You've been reading (or perhaps imagining and writing) too many anti-Ares I rants. No rocket will ever be as safe as your car; there is simply too much energy being contained in a structure that must be light enough to fly. Ares I and Orion will be safer than Mercury, Gemini, and Apollo were. I do not care for Ares or Orion, but even I can see and accept that.

I question those who calculate the safety on concepts and their ability or at the very least honesty. I also wonder where they get their numbers but I think we can safely say those numbers are not worth the paper they are printed on.

The "numbers" are of little value other than in arguing for or against any particular person's preferred architecture (just ask the crews of Challenger and Columbia). I doubt that any vehicle has ever exactly met the LOC/LOM "numbers" that were "calculated" before the 1st use of the design. I may question the notion of LOC/LOM "numbers", but that does not mean that the underlying concepts used to determine that one rocket design may be safer than another are invalid. With 1 engine per stage, Ares will have a certain basic simplicity.

It seems they don't know of things that have been developed since 1967 such as vehicle health monitoring and Kevlar shields which would allow one to escape the stack long before it's in the process of exploding.

BTW on the reliability of vehicle health monitoring and computer controls if you ever fly on an airliner or ride a train your life is depending on the reliability of such systems.

I think you go too far here. There certainly is a tendency in safety-critical operations to cling to older (proven) tech, but Kevlar and better computers may not gain as much as you think. The first sign of trouble may simply not be detectable any sooner, so your better computer may not be able to do anything earlier. Rockets contain a lot of energy and when they perform an involuntary conversion into scrap, that energy goes somewhere and throws the bits and pieces with a good deal of force; a little Kevlar may offer very little protection against a sharp-edged, meter-long, chunk of tank wall moving at Mach 1 (accompanied by a large fireball). An abort system using the technologies you hold in low regard is probably capable of getting the crew clear faster than needed and is likely being limited in this design to keep the abort G-loads on the crew survivable.