Author Topic: Can you beat a Star 48?  (Read 25820 times)

Offline LegendCJS

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Re: Can you beat a Star 48?
« Reply #20 on: 10/16/2013 06:37 PM »
Let's list the things that DONT have to change, as opposed to that V1.1 upgrade.

Avionics remain the same
Engines remain the same
Inner stage adapter remains the same.
Plumbing between tanks and the RL 10 is pretty much unchanged, although some of the pipe lengths may vary slightly.
RCS/cold gas thrusters unchanged.
Payload adapter unchanged.
etc

Rockets (and their parts) aren't legos.

Counter arguments for all your points:

Avionics remain the same - no, they need to be re-programed, and certified. and inertial sensors need their locations changed

Engines remain the same - tank size and engine capacity are closely matched.  you leave a lot of the bang for your buck on the table if you only tweak tank size and not the engines as well.

Inner stage adapter remains the same. no, new structural modes require tweaking of the inter stage adaptor, unless it was wastefully over engineered in the first place.

Plumbing between tanks and the RL 10 is pretty much unchanged, although some of the pipe lengths may vary slightly. (yes- requiring new fluid flow analysis)

RCS/cold gas thrusters unchanged. (no they need to be re positioned and angled differently to keep their through through the new center of mass)

Payload adapter unchanged.  (another structure whose lack of needing to tweak to deal with different vibration modes of the longer stage would imply it was wastefully over-engineered in the first place)
« Last Edit: 10/16/2013 06:38 PM by LegendCJS »
Remember: if we want this whole space thing to work out we have to optimize for cost!

Offline Lurker Steve

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Re: Can you beat a Star 48?
« Reply #21 on: 10/16/2013 06:54 PM »
I guess that's why I'm not a rocket scientist. Good thing I didn't estimate this job.

So, basically a tank stretch on a Centaur should never happen, since it's basically re-engineering the entire stage over again. You might as well invest that effort into the next generation upper stage, be that ACES or whatever.

Offline a_langwich

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Re: Can you beat a Star 48?
« Reply #22 on: 10/16/2013 08:52 PM »
Does a tank stretch really require an extensive development effort ?
Yes, because in this case a second RL10 would likely also have been needed, requiring development of Dual Engine Centaur.  But even just a tank stretch would require analysis and testing of its effects on flight stability and control during ascent and in-space use, on structural and bending mode issues, on the thermal effects of the longer RL10 burn, etc.  This would all be fine if it were being implemented for more than just one mission.

 - Ed Kyle

Why would it need a second engine?  Recall we are talking about a 478 kg payload on top.  And wouldn't the weight of a second engine reduce the performance of the stack, requiring even more fuel and oxidizer?  (The weight of the engine plus additional plumbing and tanking would likely be on the same order as a second payload.)  Was that included in your 4.3 tonnes figure?  Would a second engine be needed if the Centaur weren't being used to achieve a low earth orbit? 

It's really irrelevant, and I'm sure Ed and most others know this, but the DEC re-development is already well under way in order to support Commercial Crew.  Not sure what tank size is planned.

I wonder if it would be possible to use a Centaur on D4H?  Or would the price ULA charged for engineering such an arrangement be equal to the cost of finishing ACES?  Is using the 4m DCSS an option for D4H?

Offline Jim

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Re: Can you beat a Star 48?
« Reply #23 on: 10/16/2013 09:01 PM »

Rockets (and their parts) aren't legos.

Counter arguments for all your points:

RCS/cold gas thrusters unchanged. (no they need to be re positioned and angled differently to keep their through through the new center of mass)


Agree on all points except this one.  They never pointed through the center of mass because if they didn't there would be no way to rotate the vehicle.  The settling thrusters are parallel with the long axis.

But to add

Modify the VIF platforms because the payload mating plane as changed.
Modify the umbilical mast because the interface for avionics, GH2 vent, AC, GN2 purge has moved
Lengthen the 5m fairing since the stage is longer.
modify the Centaur transport GSE for the longer stage
modify the 5m fairing transport GSE for length.

Offline a_langwich

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Re: Can you beat a Star 48?
« Reply #24 on: 10/16/2013 09:33 PM »



Counter arguments for all your points:

Avionics remain the same - no, they need to be re-programed, and certified. and inertial sensors need their locations changed

This is being excessive, I think.  "re-programmed" perhaps, but the changes are likely to be changes to various constants, if the avionics suite was reasonably well-written.  Still have to run through the verification suite, but actual development is close to nil. 

Not sure, though, since Centaur is so old, the avionics software might have been completely rewritten recently (for the common avionics push?) or it could be nightmarish bit-tweaking legacy code from the 70s and 80s.  Even for legacy code, though, it would still likely be just changing some constants.


Quote
Inner stage adapter remains the same. no, new structural modes require tweaking of the inter stage adaptor, unless it was wastefully over engineered in the first place.

Payload adapter unchanged.  (another structure whose lack of needing to tweak to deal with different vibration modes of the longer stage would imply it was wastefully over-engineered in the first place)

These are also excessive.  In theory, perhaps.  But in practice, adapters that need constant tweaking are the thing that is wastefully over-engineered.  Their purpose in life is to avoid engineering custom hardware for each new situation, so if they themselves require tweaking for new situations, they are a failure.  Consider that New Horizons Pluto was 478 kg + 2140 kg for a Star 48B, whereas other potential payloads could be 7x that.  In your "shave every mg of mass" scenario, they would custom-build an adapter for each payload.

Certainly some analysis would need to be done to confirm there aren't any problems, but likely the changes to modes are well inside the design specs, since they are bounded by those heavier payloads.

Offline a_langwich

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Re: Can you beat a Star 48?
« Reply #25 on: 10/16/2013 09:58 PM »

No one has mentioned yet the Juno probe, which uses a hypergol bipropellant engine for its slowdown and maneuver burns.

http://en.wikipedia.org/wiki/LEROS

Too small to compete with a Star 48?   Or would make too heavy a stage for the same boost?  Too expensive?


Offline Jim

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Re: Can you beat a Star 48?
« Reply #26 on: 10/17/2013 12:54 AM »

Not sure, though, since Centaur is so old, the avionics software might have been completely rewritten recently (for the common avionics push?) or it could be nightmarish bit-tweaking legacy code from the 70s and 80s.  Even for legacy code, though, it would still likely be just changing some constants.


It got new avionics in 2005

Offline cleonard

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Re: Can you beat a Star 48?
« Reply #27 on: 10/17/2013 02:14 AM »

No one has mentioned yet the Juno probe, which uses a hypergol bipropellant engine for its slowdown and maneuver burns.

http://en.wikipedia.org/wiki/LEROS

Too small to compete with a Star 48?   Or would make too heavy a stage for the same boost?  Too expensive?

The Leros-1b used in Juno has less than 1% of the thrust of a Star-48.  Just run it 100x as long?  Burning quickly while sill deep in Earth's gravity helps due to a stronger Oberth effect.  The ISP on the Leros 1-b is 318 vs 292 fro the Star 48.  A difference, but not a huge difference.  You might lose a lot of the better ISP in lost Oberth effect.

How about a slightly different original question like this.  Given a standard Atlas 551 could you do better than a Star-48 as a third stage for New Horizons?

I'd say the answer is yes.  The Atlas fairing was far from filled with a Star-48 and the New Horizons spacecraft.  I think that there would be room for two Star-48's to begin with.  Even then there is a good meter plus from the outside of the 1.25 meter diameter Star-48 to the inside 3.75 meter inside diameter of the 4 meter fairing.

I'm sure that a one off UDMH-NTO third stage could do a better.  It would be expensive and risky.  Too much of both for this mission.

LH2 and LOX gives the best ISP, but volume is limited and I don't know if you could get enough inside the fairing to do better.   It would also be even more expensive.  In volume limited situations impulse density and trump specific impulse.


 

Offline savuporo

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Re: Can you beat a Star 48?
« Reply #28 on: 10/17/2013 03:11 AM »
This is being excessive, I think.  "re-programmed" perhaps, but the changes are likely to be changes to various constants, if the avionics suite was reasonably well-written. ...  Even for legacy code, though, it would still likely be just changing some constants.
Many software engineers tombstones have something like this written on them. Especially the ones that deal with embedded/hardware related coding, like avionics, robotics, automation etc. I remember saying things like these myself almost two decades ago.
Orion - the first and only manned not-too-deep-space craft

Offline R7

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Re: Can you beat a Star 48?
« Reply #29 on: 10/17/2013 08:03 AM »
Lengthen the 5m fairing since the stage is longer.
modify the 5m fairing transport GSE for length.

I don't see the need to lengthen the PLF if the intent is to modify Centaur to propel small probes to go faster. Supports between top of Centaur and PLF need to move forward though?

The interstage would have it easier because CG of US+payload would move closer to it (most mass would shift from 2+ton Star48 as payload to LOX tank on the bottom) so smaller torque forces.

Are the avionics (INS particular) on top or bottom dome? In any case don't see the need to move them anywhere from their current location.

Having said above modding Centaur to propel New Horizons may not be a good deal at all because Centaur empty weight is an order of magnitude greater than Star48B. Only ~20% of the mass reaching final speed would be payload  :o
AD·ASTRA·ASTRORVM·GRATIA

Offline RigelFive

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Re: Can you beat a Star 48?
« Reply #30 on: 10/17/2013 08:04 AM »
I may be wrong about this, but the Russian liquid Fregat upper stage (used on the Russian Phobos-Grunt mission) could be viewed as having a better spec'd performance than a Star 48.   Not that you should believe everything you read on Wikipedia, but if it is correct there is better performance in the Fregat.  The Fregat performance reported on astronautics would show it is about equivalent to a Star 48 performance.

Fregat (Ref:  wikipedia)
Fuel:  UDMH/N2O4
Isp:  327-332 seconds
Total Impulse:  26.1 MN-sec
Burn Time:  1320 seconds
# Burns:  multiple (~20)
Mass Fraction:  0.82
Total Mass: 6535 kg
Impulse-per-kg:  4085 m/s

Star 48 (Ref:  astronautica)
Fuel:  Solid
Isp:  287 seconds
Total Impulse:  5.6 MN-sec
Burn Time:  88 seconds
# Burns:  1
Mass Fraction:  0.94
Total Mass: 2114 kg
Impulse-per-kg:  2649 m/s

Offline R7

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Re: Can you beat a Star 48?
« Reply #31 on: 10/17/2013 08:25 AM »
Fregat + New Horizons: total mass 7013kg, delta-v 4.7km/s

Star48 + New Horizons: total mass 2592kg, delta-v 4.1km/s

See the problem here, 0.6km/s velocity increase but 2.7 times increase to the total mass. Unless you have bigger LV to boost the Fregat+NH to same initial speed than Star48+NH you end up going slower.
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Offline MP99

Re: Can you beat a Star 48?
« Reply #32 on: 10/17/2013 09:31 AM »
Modify the VIF platforms because the payload mating plane as changed.

So, the interface is from LV to STAR, and the STAR-to-S/C interface is "the payload's problem"? Is any access provided for the STAR-to-S/C interface?


Lengthen the 5m fairing since the stage is longer.

Ed's "20% stretch" post suggests the Centaur would be lengthened by about the same amount as the length of the STAR 48, so would the payload be positioned much differently than with STAR?

cheers, Martin

Offline Jim

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Re: Can you beat a Star 48?
« Reply #33 on: 10/17/2013 12:12 PM »

1.  I don't see the need to lengthen the PLF if the intent is to modify Centaur to propel small probes to go faster. Supports between top of Centaur and PLF need to move forward though?

2. Are the avionics (INS particular) on top or bottom dome? In any case don't see the need to move them anywhere from their current location.


1. The 5m fairing is two sections with one section going around the Centaur.  This section would have to be lengthened.

2.  They are on the forward adapter and any changes to the location of the forward adapter (tank length) means all the umbilicals and access would have to be changed.


Offline Jim

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Re: Can you beat a Star 48?
« Reply #34 on: 10/17/2013 12:18 PM »

1.  So, the interface is from LV to STAR, and the STAR-to-S/C interface is "the payload's problem"? Is any access provided for the STAR-to-S/C interface?

2.  Ed's "20% stretch" post suggests the Centaur would be lengthened by about the same amount as the length of the STAR 48, so would the payload be positioned much differently than with STAR?


1. The spacecraft and STAR are mated in the payload processing facility and encapsulated there.

2.  The lower half of the fairing (base section) would have to stretched and hence the top of the Centaur and relationship to the fairing would not change.

The 5m fairing comes in two sections.  The base section is installed around the Centaur at the VIF and the payload section is installed around the space vehicle at the payload processing facility


 

Offline MP99

Re: Can you beat a Star 48?
« Reply #35 on: 10/17/2013 02:53 PM »
Thanks, Jim.

Cheers, Martin

Offline a_langwich

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Re: Can you beat a Star 48?
« Reply #36 on: 10/19/2013 06:38 AM »

http://www.spacenews.com/article/launch-report/37757nasa-mulls-common-upper-stage-for-launch-services-catalog


Quote from: Dan Leone at SpaceNews
Aerojet and Orbital were asked to design a reference mission for NASA that shows how quickly the companies’ chosen upper stages — whatever those may be — could propel a payload beyond Earth assuming launch by a rocket approximately as powerful as Space Exploration Technologies Corp.’s (SpaceX) Falcon 9 v1.1. That launcher, which flew for the first time Sept. 29, can send about 13 tons to low Earth orbit, or about 4.9 tons to geostationary transfer orbit, using the kerosene-fueled upper stage SpaceX built for it. Orbital Sciences’ rockets, including the Antares rocket that launched the Cygnus cargo tug to the international space station in September, use solid-fueled upper stages.

Maybe this is a stretch, but seems like a very similar question to what I was asking.  Except NASA is offering $300k for answers.  :D   That is, in view of NASA's science missions, maximize for C3, instead of maximizing payload for one of LEO/GTO/TLI. 

Given the fondness NASA missions had for the Delta II in the past, perhaps they think the Falcon 9 and Antares fit in the sweet spot for such a focus.  And, as it happens, both vehicles seem limited at present to LEO roles because they don't have well-defined high energy upper stage options.

Another thought:  the article focuses on Orbital's experience with solids, which is true for launch vehicles.  So maybe they will look at ATK Star XXs to fill this role.  But doesn't Orbital the satellite and Cygnus maker also have a fair amount of experience with hypergolic engines?  So I'd like to think they might consider options using those as well.  I think they offer both storable and solid upper stage options for Antares, too.

The other award went to Aerojet Rocketdyne, which seems a bit odd at first glance to me...of course they make the RL-10, but the actual upper stages (Centaur and DCSS) are made by ULA, right?  Or is Boeing IDS still separate from ULA?  But while Rocketdyne does the RL-10, Aerojet also does hypergols and solids too, don't they?  So maybe that's the thought.

I wonder if ULA and SpaceX wouldn't be interested in specifying solutions here?  SpaceX might pay close attention here, because Falcon Heavy might be significantly more marketable with better high energy options mapped out.  Those NASA science guys who do almost all of the high energy missions are cheapskates of necessity, so FH might be possible where D4H is not.

ULA might not be too eager to design upper stages for Falcon/Antares.  On the other hand, one of the ground rules was that the satellite interface would have to be the same as Atlas/Delta, and it's conceivable a modified Centaur might fill the gap nicely.  Depending on the profit margins for the upper stage, might ULA be happy to use those new launch vehicles as an opportunity to pioneer something like ACES?  After a flight or two on the competition, they could offer it on their own launch vehicles as already proven (but in the case of say an Atlas V "55A" vastly more capable). 

I suppose it depends on how ULA views the likelihood/desirability of getting a launch client for ACES or other new upper stage designs, whether for science or military or DUUS, and whether they want to use the upper stages to lock customers into Atlas/Delta or view them as separate profit centers.  If ULA were serious about prop depots, this would be an excellent opportunity to arrange a (ahem, built-by-ULA) depot-compatible upper stage could be flown by all the current launch vehicles.  Jus' sayin'. 

Not sure $300k buys a very thorough trades study, though.  Might just be an intern thumbing through the various product catalogs, copying some specs, and putting it in a pretty proposal.  In which case, I'd like to offer my services, with very very low overhead.  :)

Offline Jim

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Re: Can you beat a Star 48?
« Reply #37 on: 10/19/2013 05:48 PM »

http://www.spacenews.com/article/launch-report/37757nasa-mulls-common-upper-stage-for-launch-services-catalog


Quote from: Dan Leone at SpaceNews
Aerojet and Orbital were asked to design a reference mission for NASA that shows how quickly the companies’ chosen upper stages — whatever those may be — could propel a payload beyond Earth assuming launch by a rocket approximately as powerful as Space Exploration Technologies Corp.’s (SpaceX) Falcon 9 v1.1. That launcher, which flew for the first time Sept. 29, can send about 13 tons to low Earth orbit, or about 4.9 tons to geostationary transfer orbit, using the kerosene-fueled upper stage SpaceX built for it. Orbital Sciences’ rockets, including the Antares rocket that launched the Cygnus cargo tug to the international space station in September, use solid-fueled upper stages.

Maybe this is a stretch, but seems like a very similar question to what I was asking.  Except NASA is offering $300k for answers.  :D   That is, in view of NASA's science missions, maximize for C3, instead of maximizing payload for one of LEO/GTO/TLI. 

Given the fondness NASA missions had for the Delta II in the past, perhaps they think the Falcon 9 and Antares fit in the sweet spot for such a focus.  And, as it happens, both vehicles seem limited at present to LEO roles because they don't have well-defined high energy upper stage options.

Another thought:  the article focuses on Orbital's experience with solids, which is true for launch vehicles.  So maybe they will look at ATK Star XXs to fill this role.  But doesn't Orbital the satellite and Cygnus maker also have a fair amount of experience with hypergolic engines?  So I'd like to think they might consider options using those as well.  I think they offer both storable and solid upper stage options for Antares, too.

The other award went to Aerojet Rocketdyne, which seems a bit odd at first glance to me...of course they make the RL-10, but the actual upper stages (Centaur and DCSS) are made by ULA, right?  Or is Boeing IDS still separate from ULA?  But while Rocketdyne does the RL-10, Aerojet also does hypergols and solids too, don't they?  So maybe that's the thought.

I wonder if ULA and SpaceX wouldn't be interested in specifying solutions here?  SpaceX might pay close attention here, because Falcon Heavy might be significantly more marketable with better high energy options mapped out.  Those NASA science guys who do almost all of the high energy missions are cheapskates of necessity, so FH might be possible where D4H is not.


No, it is not odd for Aerojet to get this, they make solids and also PBV's.
It is not a task for ULA or Spacex.
This not  for Delta II replacement, the NASA will ask the launch service contractors to provide all the velocity required, NASA isn't going to stick an upperstage on F9 or Antares. If the F9 or Antares doesn't meet the requirements of a Delta II class mission, the Spacex or OSC will have to engineer the solution, NASA isn't going to add an upperstage.
This is for an upperstage similar to what Pluto New Horizons used.  Its first potential use is for Solar Probe Plus.
« Last Edit: 10/19/2013 05:54 PM by Jim »

Offline ugordan

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Re: Can you beat a Star 48?
« Reply #38 on: 10/19/2013 06:01 PM »
This is for an upperstage similar to what Pluto New Horizons used.  Its first potential use is for Solar Probe Plus.

Is the Star 48B not preferred any more for some reason? Do we know more about the study requirements, e.g. what is the reference payload mass they want to maximize the C3 for?

Offline Jim

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Re: Can you beat a Star 48?
« Reply #39 on: 10/19/2013 06:13 PM »
This is for an upperstage similar to what Pluto New Horizons used.  Its first potential use is for Solar Probe Plus.

Is the Star 48B not preferred any more for some reason? Do we know more about the study requirements, e.g. what is the reference payload mass they want to maximize the C3 for?

They want the whole solution with guidance system

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