Author Topic: DIRECT v2.0 - Thread 3  (Read 1123320 times)

Offline A_M_Swallow

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Re: DIRECT v2.0 - Thread 3
« Reply #420 on: 01/20/2009 05:00 am »
{snip}
I know Ross was mentioning earlier that with Ares 1, Orion would have to do a SM burn to get it to the ISS.  Didn't know if that's the case with the J120.

All spacecraft need to use their engines to dock.  This is similar to using first gear to pack a car.  One of the problems with Ares I is the Orion SM also has to use its engine to get to LEO.

Offline zapkitty

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Re: DIRECT v2.0 - Thread 3
« Reply #421 on: 01/20/2009 05:25 am »

All spacecraft need to use their engines to dock.  This is similar to using first gear to pack a car.  One of the problems with Ares I is the Orion SM also has to use its engine to get to LEO.

I was thinking that was what Lobo was recalling. But as you say the actual reference was to the fact that Ares-1, at the end of its second stage burn, delivers Orion to a final trajectory that ends up parking the Orion 11 miles underground... forcing the Orion SM to waste its own fuel doing a "third stage" burn.

Which makes for more silliness.... an actual Ares-1 third stage!... ....what?... what do you mean it's baselined for 2018?...

Offline sandrot

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Re: DIRECT v2.0 - Thread 3
« Reply #422 on: 01/20/2009 05:51 am »
[...]

Which makes for more silliness.... an actual Ares-1 third stage!... ....what?... what do you mean it's baselined for 2018?...

Delta v provided by Orion for orbit insertion is not so different from delta v provided by OMS during shuttle orbit insertion. Get your facts, no 3rd stage...
"Paper planes do fly much better than paper spacecrafts."

Offline kkattula

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Re: DIRECT v2.0 - Thread 3
« Reply #423 on: 01/20/2009 06:25 am »
[...]

Which makes for more silliness.... an actual Ares-1 third stage!... ....what?... what do you mean it's baselined for 2018?...

Delta v provided by Orion for orbit insertion is not so different from delta v provided by OMS during shuttle orbit insertion. Get your facts, no 3rd stage...

IIRC, it's about one third greater.

However Shuttle OMS is also often used during main engine burn to augment the SSME's. So Shuttle OMS is really the third stage on this supposed SSTO. ;)

Offline sandrot

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Re: DIRECT v2.0 - Thread 3
« Reply #424 on: 01/20/2009 06:33 am »
IIRC it's closer to 1/5th greater. US must be discarded just like ET...

AND we don't like popcorns on orbit.
« Last Edit: 01/20/2009 06:36 am by sandrot »
"Paper planes do fly much better than paper spacecrafts."

Offline zapkitty

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Re: DIRECT v2.0 - Thread 3
« Reply #425 on: 01/20/2009 07:19 am »
But the Ares-1 numbers at all-burnt can't-do-any-better are a perigee ~-61 miles lower than shuttle, the last 11 of those being underground (or underwater...)

The danger is not popcorns, as popcorns are not in the picture for Ares-1. The danger is groundhogs (or giant squids...)

And the shuttle numbers are voluntary, as the ET could theoretically power the orbiter all the way up to orbit at no danger to the mission. (The current mission that is, the resultant popcorns and hazards to later missions from such an action are another story...)

(Hmmm... and what are the percentages of total available delta v for the shuttle OMS vs the Aries-1 launched Orion SM that are eaten by this maneuver?)

So at this time, when the Ares-1 launched Orion is desperately evading giant squids... I still think it's a third stage :)


Offline clongton

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Re: DIRECT v2.0 - Thread 3
« Reply #426 on: 01/20/2009 11:27 am »
Shuttle OMS burn for orbital insertion is voluntary.
Shuttle SSME with ET attached is capable of placing Shuttle into a stable orbit. STS chooses not to do that to enable a simple atmospheric disposal of the ET, but it doesn't have to.

Here's the difference:

Launched by Ares-I, Orion 1st SM burn is IN-voluntary because:
Ares-I SECO with empy tanks *cannot* place Orion into a stable orbit.
Orion 1st SM burn is designed to get Orion to the point where the 2nd SM burn can do an orbital insertion.
Therefore Orion's 1st SM  burn functions as a launch vehicle burn to make up for Ares-I inability.
Therefore Orion's 1st SM burn is a launch vehicle third stage burn.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline Kaputnik

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Re: DIRECT v2.0 - Thread 3
« Reply #427 on: 01/20/2009 11:48 am »
I think the numbers are more important than the semantics.
How much SM propellant is used up in achieving a stable orbit?
"I don't care what anything was DESIGNED to do, I care about what it CAN do"- Gene Kranz

Offline Jim

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Re: DIRECT v2.0 - Thread 3
« Reply #428 on: 01/20/2009 11:58 am »
[...]

Which makes for more silliness.... an actual Ares-1 third stage!... ....what?... what do you mean it's baselined for 2018?...

Delta v provided by Orion for orbit insertion is not so different from delta v provided by OMS during shuttle orbit insertion. Get your facts, no 3rd stage...

And the OMS is a 3rd stage of the shuttle.  Get your facts straight

Offline wannamoonbase

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Re: DIRECT v2.0 - Thread 3
« Reply #429 on: 01/20/2009 12:31 pm »
I took a few days off from reading this thread and it looks like I came back to a heated discussion about SM and OMS.

All of the speculation about Ares and Direct and Ares V changing back to SSME has had me thinking about all of the combination of equipment and problems with cost and schedule.

It leaves me, possibly as a population of 1, supporting using the NLS designs of old.  Existing 4 segment boosters, SSMEs and ET diameter and tooling.  There is nothing to develop or manrate.  The tank would be redesigned and developed but you don't need to put hundreds of millions (lets face it billions) into manrating the RS-68 or 5 segment boosters.

Over time you can evolve the SSME to a cheaper disposable model and 5 segment boosters.

It's the least amount of development.

As I posted in the Ares 1 efficiency thread, the new vehicle needs to get flying ASAP.  Delays cost money and increases questions and doubts.

That is all.
Wildly optimistic prediction, Superheavy recovery on IFT-4 or IFT-5

Offline Yegor

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Re: DIRECT v2.0 - Thread 3
« Reply #430 on: 01/20/2009 01:08 pm »
If a launch vehicle is used to do both kind of launches crew or cargo, does it increase safety?

For example Russian Soyuz LV used to launch crew but it also used to launch cargo so the crew was launched in some 1 out of 4 launches of Soyuz LV. Several years ago there was Soyuz LV accident during cargo launch. So the probability of accident during a crew launch is just 1 out of 4 or four times smaller.

Accidents happen occasionally even with US launchers - there was Atlas V Centaur accident couple of years ago.

I think that it adds to DIRECT safety.


Offline Ronsmytheiii

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Re: DIRECT v2.0 - Thread 3
« Reply #431 on: 01/20/2009 01:27 pm »
[...]

Which makes for more silliness.... an actual Ares-1 third stage!... ....what?... what do you mean it's baselined for 2018?...

Delta v provided by Orion for orbit insertion is not so different from delta v provided by OMS during shuttle orbit insertion. Get your facts, no 3rd stage...

And the OMS is a 3rd stage of the shuttle.  Get your facts straight

With most other systems the boosters are considered the 0 stage and the core would be the 1st stage, so wouldnt that make the OMS burn the 2nd stage?

Offline Will

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Re: DIRECT v2.0 - Thread 3
« Reply #432 on: 01/20/2009 01:40 pm »
Well, I did a little bit of modeling,  assuming we want to fuel the Jupiter EDS with 248,000 pounds of fuel, assumeing that the Falcon 9H, Atlas 5H are now available, that the Soyuz Fregat launches from French Guina, and that the Delta II is still in service, that you could fuel the things with

1 Atlas V Heavy
1 Atlas V 551
1 Delta IV HEAVY
2 Delta 2 7920H
1 Airane v
1 Soyuz Fregat

At a launch cost of about 1.26 Billion dollars at current launch prices.  With a 15% profit, it would run you about 1.5 Billion bucks to send the fuel up.

Just my thoughts.

That gets you to orbit, but not to the depot. That final step requires a tug of some kind.

Current state of the art is an attached, single use tug, which seems to cost about as much as the launch.

A reusable tug is certainly possible, but more complex and more expensive to develop. At a high flight rate it would cost less than an expendable tug, but the operating costs are uncertain. At a minimum, you'd need to bring up more propellant to refuel the tug.
« Last Edit: 01/20/2009 05:28 pm by Will »

Offline Jorge

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Re: DIRECT v2.0 - Thread 3
« Reply #433 on: 01/20/2009 01:40 pm »
Shuttle OMS burn for orbital insertion is voluntary.
Shuttle SSME with ET attached is capable of placing Shuttle into a stable orbit. STS chooses not to do that to enable a simple atmospheric disposal of the ET, but it doesn't have to.

Incorrect. That would require an SSME restart at apogee (nominal OMS-2 position) and the current SSME is incapable of in-flight restart.

There is nothing "voluntary" about OMS-2, unless you like AOA aborts.
JRF

Offline Oberon_Command

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Re: DIRECT v2.0 - Thread 3
« Reply #434 on: 01/20/2009 01:46 pm »
Shuttle OMS burn for orbital insertion is voluntary.
Shuttle SSME with ET attached is capable of placing Shuttle into a stable orbit. STS chooses not to do that to enable a simple atmospheric disposal of the ET, but it doesn't have to.

Incorrect. That would require an SSME restart at apogee (nominal OMS-2 position) and the current SSME is incapable of in-flight restart.

There is nothing "voluntary" about OMS-2, unless you like AOA aborts.


You're saying that the shuttle can't insert itself into orbit straight off the pad by flying a different trajectory that doesn't require an OMS-2 or equivalent burn? Why not?

Offline clongton

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Re: DIRECT v2.0 - Thread 3
« Reply #435 on: 01/20/2009 02:09 pm »
Shuttle OMS burn for orbital insertion is voluntary.
Shuttle SSME with ET attached is capable of placing Shuttle into a stable orbit. STS chooses not to do that to enable a simple atmospheric disposal of the ET, but it doesn't have to.

Incorrect. That would require an SSME restart at apogee (nominal OMS-2 position) and the current SSME is incapable of in-flight restart.

There is nothing "voluntary" about OMS-2, unless you like AOA aborts.


I said a stable orbit, not a useful orbit. Shuttle is "capable" of achieving orbit without an OMS burn, as opposed to "requiring" an OMS burn because of the SSME/ET being incapable of it, as is the sitiation with Ares-I.

That's the difference. Shuttle does not *HAVE* to do an OMS burn to achieve orbit, but Ares-I/Orion DOES.
« Last Edit: 01/20/2009 02:11 pm by clongton »
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline Lee Jay

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Re: DIRECT v2.0 - Thread 3
« Reply #436 on: 01/20/2009 02:24 pm »
I said a stable orbit, not a useful orbit.

You also said this:

Quote
Insert itself and the spacecraft directly into a circular orbit of the correct altitude and inclination.

How is that accomplished with J-120?

Offline William Barton

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Re: DIRECT v2.0 - Thread 3
« Reply #437 on: 01/20/2009 02:34 pm »
I am a little confused by the 3rd-stage debate going on here. Doubtless, this is due to my deficient knowledge, so I'm asking for a little enlightenment here. I understand a cicularization burn is done often at apogee, which has the effect of raising the perigee, but is that actually required? And if required for perfectly circular orbits, certainly not for stable eliptical orbits in which the perigee is above the sensible atmosphere? Sputnik I and Atlas SCORE were both put in orbit by 1.5-stage LVs, for example. And Skylab was put aloft by a 2-stage Saturn that had no restart capability. So what am I not getting here? A two-stage LV ought to be able to follow a synergy-curve trajectory that gets it into something pretty close to a circular orbit.
« Last Edit: 01/20/2009 02:36 pm by William Barton »

Offline Herb Schaltegger

Re: DIRECT v2.0 - Thread 3
« Reply #438 on: 01/20/2009 02:41 pm »
Shuttle OMS burn for orbital insertion is voluntary.
Shuttle SSME with ET attached is capable of placing Shuttle into a stable orbit. STS chooses not to do that to enable a simple atmospheric disposal of the ET, but it doesn't have to.

Incorrect. That would require an SSME restart at apogee (nominal OMS-2 position) and the current SSME is incapable of in-flight restart.

There is nothing "voluntary" about OMS-2, unless you like AOA aborts.


Jorge - is the STS system capable of orbit (w/ET attached, since that seems to be part of the debate) without an OMS-2 if you're willing to accept an elliptical orbit?
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Offline Ben the Space Brit

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Re: DIRECT v2.0 - Thread 3
« Reply #439 on: 01/20/2009 02:44 pm »
I said a stable orbit, not a useful orbit.

You also said this:

Quote
Insert itself and the spacecraft directly into a circular orbit of the correct altitude and inclination.

How is that accomplished with J-120?

I'm no expert (indeed, I only have minimal knowledge).  However, if someone were to ask me to plan such a flight, I'd do something like this.

I would launch the J-120 into an unstable elliptical insertion orbit that re-enters the atmosphere on the other side of apogee (say about 135nm apogee, 50nm perigee).  The apogee should be as close as is practical to the final mission orbit altitude.  The Orion seperates from the LV, coasts up to apogee and fires its SMME (Service Module Main Engine) at that point to circularise the orbit.  The J-120 and payload fairing (not to mention any loose insulation), having not changed orbit, would hit the atmosphere at a moderate angle and burn up.

The other orbit option for the J-120 is to push all the way up to the best circular orbit available, seperate and then deorbit the LV using retros (basically ulage thrusters pointing the wrong way).  The Orion, which has sufficient fuel for the ROI burn from Low Lunar Orbit, is then free to use its SMME to make whatever orbit altitude control burns as the mission plan requires.

@ William Barton

It all depends on what you want to do with the mission and what the perigee altitude is. 

As has been pointed out, the perigee after AIUS burn is actually below mean sea level on Earth, so the next burn to raise the perigee is not only desirable, it is mission critical.  On the other hand, many early manned spaceflights deliberately used lop-sided orbits with a very low perigee to ensure that, should the de-orbit retros fail, the vehicle's orbit would automatically decay and allow the crew to return in a hair-raising but survivable ballistic re-entry.

Lop-sided insertion orbits are also useful as they allow you to sneak in a much higher orbit than would normally be possible with the LV.  I gave an example above.  In summary, you launch into an unstable decaying orbit with a high apogee and use a circularisation burn at the apogee to 'steal' a higher stable orbit than would be possible with the LV alone.  The shuttle currently uses this strategy, unless I am badly misinformed.

It is true that any LV could, theoetically, offer a circular orbit at the end of its burn.  However, given that Ares-I's planned post-US trajectory will be 100 (apogee) x -11 (perigee), I would imagine that a circular or near-circular trajectory for the type would be uncomfortably deep inside the upper atmosphere.
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