Author Topic: Antares A-One General Discussion Thread (2)  (Read 46591 times)

Offline strangequark

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Re: Antares A-One General Discussion Thread (2)
« Reply #40 on: 04/17/2013 10:32 PM »
You know, I don't understand the choice of a solid U/S.  It seems to have all the wrong attributes for an U/S.

Solids, IIUC, have a high "dry" weight, since the entire "tank" is thick walled.  And in an U/S, every pound wasted is 100% at the expense of payload.
This is actually kind of a misconception when you're talking about composite solids. The PMF on the Castor 30 is 0.926, which is pretty damn good (you can confirm this yourself, if you search for the ATK Motor Catalog).

Also, it burns to depletion, so you can't control end-of-burn, so I'd think that precision insertion is problematic.
Yes, but modern GNC is pretty skilled at minimizing this uncertainty to the point where it's a non-issue for the payload to take up the slack.

Lastly, it is not a high ISP solution.
This point I will still give you. Even the kerosene upper stage engines are pretty good by comparison.

Offline Kabloona

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Re: Antares A-One General Discussion Thread (2)
« Reply #41 on: 04/17/2013 10:47 PM »


Anyone familiar with why they went with a solid U/S?

IIRC, Antonio said they decided that doing a liquid first stage for the first time (for Orbital) was enough of a challenge, and that trying to simultaneously develop a liquid upper stage would have been biting off more than they could chew. An off-the-shelf solid was a lower technical and schedule risk proposition.

And also it was at one point planned to upgrade to a liquid U/S using, IIRC, a Soyuz engine. I believe that plan is shelved at present though (shame!)

Yes, since the 30XL will improve performance and the Star 48 can be stacked on top as well. No business case to develop an (expensive) cryo 2nd stage at this point in the game.

Offline Big Al

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Re: Antares A-One General Discussion Thread (2)
« Reply #42 on: 04/17/2013 11:09 PM »
Since the Star family of engines has been around for a long time, It's burn profile is well known.
Also since their capsule is not equipped with a heat shield, they should be able to carry more payload for the same weight.

Offline Jim

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Re: Antares A-One General Discussion Thread (2)
« Reply #43 on: 04/17/2013 11:14 PM »
Why is it that Russians launch rockets in the middle of a snow storm / blizzard but in the US we have to worry about low cloud cover?

visibility for Range safety

Offline jsmjr

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Re: Antares A-One General Discussion Thread (2)
« Reply #44 on: 04/17/2013 11:14 PM »
From the closed processing thread:

I note the mission timeline viewgraph at the briefing shows a launch azimuth of 107.8 deg. But the actual hazard area seems to be more like an azimuth of 124 deg, and it needs to turn to an azimuth of 134 deg or so to reach the target inclination.

Does anyone have a screen shot of the cited slide? 

And any confirmation of what's going on here, doglegging like that?  Is it a function of the way the vehicle sits on the pad?  How quickly does it turn?
« Last Edit: 04/17/2013 11:15 PM by jsmjr »

Offline meekGee

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Re: Antares A-One General Discussion Thread (2)
« Reply #45 on: 04/17/2013 11:43 PM »

Yes, since the 30XL will improve performance and the Star 48 can be stacked on top as well. No business case to develop an (expensive) cryo 2nd stage at this point in the game.

Well, the business case has to do with the capacity of the overall rocket.

Right now, Antares can lift about as much as the F5 was supposed to, but that was a market spot that proved unsuccessful. 

Part of the reason for this performance is the second stage. (The ISP, 7.3% dry weight)

Also, the flip side of the business equation is cost.  Development cost may have been lower, but overall I believe the rocket is more expensive.

Correct me if I'm wrong, but at the price/capacity of Antares, is it competitive in the commercial arena?

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Offline Jim

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Re: Antares A-One General Discussion Thread (2)
« Reply #46 on: 04/18/2013 01:00 AM »
It is a Delta II replacement.

It wasn't the market that killed F5, it couldn't  do a Dragon spacecraft was the reason.  The market still exists.  See the last Delta II sold.
« Last Edit: 04/18/2013 01:04 AM by Jim »

Offline meekGee

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Re: Antares A-One General Discussion Thread (2)
« Reply #47 on: 04/18/2013 03:05 AM »
It is a Delta II replacement.

It wasn't the market that killed F5, it couldn't  do a Dragon spacecraft was the reason.  The market still exists.  See the last Delta II sold.

But isn't that setting the bar pretty low in terms of commercial market?

The Delta II is a pretty expensive rocket isn't it?

I'm looking here:  http://en.wikipedia.org/wiki/List_of_Thor_and_Delta_launches_(2010%E2%80%932019)

And I don't know which is the last sale you're referring to, but it looks like 4-5 launches a year, mostly small government payloads.
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Offline Jim

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Re: Antares A-One General Discussion Thread (2)
« Reply #48 on: 04/18/2013 03:24 AM »

But isn't that setting the bar pretty low in terms of commercial market?

The Delta II is a pretty expensive rocket isn't it?


Not commercial market, but market.  Delta II also did Globalstar and Iridium constellations.

It beat out F9 for 4 launches.

Offline meekGee

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Re: Antares A-One General Discussion Thread (2)
« Reply #49 on: 04/18/2013 05:15 AM »

But isn't that setting the bar pretty low in terms of commercial market?

The Delta II is a pretty expensive rocket isn't it?


Not commercial market, but market.  Delta II also did Globalstar and Iridium constellations.

It beat out F9 for 4 launches.

So this answers the "why" from a few posts ago.  A new rocket is always fun, but if the upside is just a delta II replacement then it's less exciting to me than what's in those other forums you complain that I frequent too much...

And beating out the newcomer on some government flights is really not a major bragging point. OSC has been around for much longer, and so it's their lead to lose.

But hey - the more the merrier, and I really don't see these two companies headed for the same market area, so there isn't even real competition.  There's some overlap on ISS cargo delivery, but in the grand scheme of things, they can't survive on that alone.  The whole point is that they find other markets, and it looks like they all can, so beers all around.
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Offline mikes

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Re: Antares A-One General Discussion Thread (2)
« Reply #50 on: 04/18/2013 07:49 AM »
Why is it that Russians launch rockets in the middle of a snow storm / blizzard but in the US we have to worry about low cloud cover?

visibility for Range safety

Are there also concerns about reflected sound, or is Antares too small for that to be a problem?

Offline Kim Keller

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Re: Antares A-One General Discussion Thread (2)
« Reply #51 on: 04/18/2013 11:58 AM »
Are there also concerns about reflected sound, or is Antares too small for that to be a problem?


There was discussion of that during the count.

Offline kevin-rf

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Re: Antares A-One General Discussion Thread (2)
« Reply #52 on: 04/18/2013 01:16 PM »

So this answers the "why" from a few posts ago.  A new rocket is always fun, but if the upside is just a delta II replacement then it's less exciting to me than what's in those other forums you complain that I frequent too much...

Other than, which is in the Orbital threads somewhere, at that point in time ULA had it's EELV solutions, but the (at that point) lower cost Delta II left a capability gap that Orbital feared would jack up the launch prices of Delta II class sized payloads that must fly on US launchers, thus putting many of these payloads into a cost death spiral that would cost Orbital Delta II sized satellite business. Orbital did not get into the business to challenge established launch providers, but to fill a gap that they feared would cost them satellite contracts. Hence the Antares was born.

And if you want to put a SpaceX spin on it, they feared the then plans of SpaceX would not meet the Delta II class payload needs of it's satellite business. If they had confidence in SpaceX, they most likely would not have built the Antares.
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Offline Lurker Steve

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Re: Antares A-One General Discussion Thread (2)
« Reply #53 on: 04/18/2013 01:34 PM »

Yes, since the 30XL will improve performance and the Star 48 can be stacked on top as well. No business case to develop an (expensive) cryo 2nd stage at this point in the game.

Well, the business case has to do with the capacity of the overall rocket.

Right now, Antares can lift about as much as the F5 was supposed to, but that was a market spot that proved unsuccessful. 

Part of the reason for this performance is the second stage. (The ISP, 7.3% dry weight)

Also, the flip side of the business equation is cost.  Development cost may have been lower, but overall I believe the rocket is more expensive.

Correct me if I'm wrong, but at the price/capacity of Antares, is it competitive in the commercial arena?



I took my non-rocket scientist look at the second stage and was actually suprised. The Castor 30 motor actually supplies more total thrust than any equivalent liquid second stage (including both the engine and motor) of comparable launch weight. It wasn't really even close.

The only issue I see with a solid second stage is that you lose the ability to restart because you really only get a single burn. That means it's near impossible to deploy multiple payloads from the same LV. Of course, since the launcher isn't oversized anyway, that's not an issue.


Offline Kabloona

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Re: Antares A-One General Discussion Thread (2)
« Reply #54 on: 04/18/2013 01:59 PM »
Back to the launch attempt...has there been any discussion of an irregular shaped white piece of material that appears to be falling off the strongback? It appears in the gif that LeeJay posted on pg 11 of the Updates thread, in the second frame of the gif. It partially obscures a horizontal member of the strongback, at a height between the A and N of Antares. It doesn't appear in frame 1, then does appear in frame 2.

Maybe some rational explanation for it, but I can't figure it out.

Edit: after looking at the video, it looks like a piece of material that was attached to the strongback and can be seen fluttering in the breeze. The first frame of LeeJay's gif that doesn't show it must have been from a different time in the count.

Edit 2: shortly after the LD calls "meet me on Anomaly 1," a white piece of material appears to fall off the fwd end of stage 1 and flutters to the ground. Shortly after that, another white piece of material falls off and hangs up on an upper horizontal member of the strongback (this is the piece I first noticed). Wondering if these are decals that fell off. IIRC someone else mentioned they were having a problem with decals adhering.
« Last Edit: 04/18/2013 02:30 PM by Kabloona »

Offline Nickolai

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Re: Antares A-One General Discussion Thread (2)
« Reply #55 on: 04/18/2013 02:04 PM »
Good question Kabloona. Looks like it might have some red paint on it?

Unrelated question - could somebody talk about the orbital mechanics going on here? Apparently, if Friday doesn't work out, it's the last opportunity for 'this part of the month' - why doesn't a launch window to a 51.6 degree orbit open every day?

And since this is just a test flight with a dummy payload, what does it matter what orbit they go to? Or is the target orbit driven by the secondary payloads?

Online douglas100

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Re: Antares A-One General Discussion Thread (2)
« Reply #56 on: 04/18/2013 02:11 PM »

The only issue I see with a solid second stage is that you lose the ability to restart because you really only get a single burn. That means it's near impossible to deploy multiple payloads from the same LV. Of course, since the launcher isn't oversized anyway, that's not an issue.

There is an option for a bi-propellant third stage which might address that need.

http://www.orbital.com/NewsInfo/Publications/Antares_Brochure.pdf
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Offline LouScheffer

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Re: Antares A-One General Discussion Thread (2)
« Reply #57 on: 04/18/2013 02:27 PM »

I took my non-rocket scientist look at the second stage and was actually suprised. The Castor 30 motor actually supplies more total thrust than any equivalent liquid second stage (including both the engine and motor) of comparable launch weight. It wasn't really even close.


The problem with this analysis is that thrust is not the right metric - you want total velocity change, or delta-V.  A liquid stage might give you 1/5 the thrust, but for 7 times longer, and be a better deal. 

Offline mr. mark

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Re: Antares A-One General Discussion Thread (2)
« Reply #58 on: 04/18/2013 02:30 PM »
Antares has been on the pad a while. We don't need another corroded nut.

Offline Antares

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Re: Antares A-One General Discussion Thread (2)
« Reply #59 on: 04/18/2013 02:52 PM »
Unrelated question - could somebody talk about the orbital mechanics going on here? Apparently, if Friday doesn't work out, it's the last opportunity for 'this part of the month' - why doesn't a launch window to a 51.6 degree orbit open every day?

And since this is just a test flight with a dummy payload, what does it matter what orbit they go to? Or is the target orbit driven by the secondary payloads?

Wallops Range availability is the driver.  Orbital targeting has no impact.  Note the launch time doesn't change with the launch date.
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