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#180 by Jim on 06 Dec, 2014 18:31
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Sorry if this has already been answered, but in the video of the launch taken from the service gantry it looked like a few wires remained attached to the rocket until it had risen a couple hundred feet. Does anyone know what those do and why they stay attached so long?
I believe it is some kind of a LOIS (liftoff instrumentation system) -
#181 by Yeknom-Ecaps on 07 Dec, 2014 02:00
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Any idea when USS Achorage and USNS Salvor will return to port? Any photos of the return? How long until they unload Orion?
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#182 by yg1968 on 07 Dec, 2014 04:16
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I am sure that this has been asked before but why was Orion black (and not white)?
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#183 by SpinGravity on 07 Dec, 2014 05:49
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Greetings all.
Please forgive my ignorance, but I have seen numerous reports stating Orion is the capsule that will go to Mars and Back. The latest launch was to test the heat shield for very high speed re-entry?
Why?
How is it more efficient to take an Earth re-entry vehicle to Mars and Back?
I was under the impression that that the mission would be assembled at ISS. Launched from ISS. Recovered to ISS.
Leave the ride home in LEO.
The single-launch to Mars idea seems marginal at best for any results. And if there will be multiple launches and assembly in LEO, then why take the re-entry vehicle along? Is someone afraid the ISS will fall down before they get back?
Would it really save resources to take it along? Seems like a lot of mass to haul on a possibly 200 million mile round trip. Seems like a lot of fuel and other consumables could take up that mass fraction.
Where is the flaw in my thinking please? I must be missing something. Are the fuel requirements to slow down to dock with ISS on the way home the issue?
Are we just going to jettison everything but the re-entry vehicle upon arrival back at Earth?
A Mars transfer module would seem to be a re-usable asset, that would need refit for another mission.
I am nowhere near as informed as I would wish to be on this particular subject, but there seems to be a disconnect somewhere between the laws of orbital mechanics and what my common sense is telling me.
I was thinking along the lines of four to five launches, with assembly and insertion from ISS. Then I see all this Orion to Mars media coverage. All I could think of was two years of spam in a can. Null G? All the way there and back? Puffy-faced skinny people on TV selling space discovery? 9 G re-entry after all of that?
Again, I ask myself, what am I missing?
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The discovery and knowledge gained, as well as the pure human need to push, makes a trip to Mars a requirement in my opinion. But unless we want government and military funding everything, there is a genuine need to get industry and especially tourism into space. There must be a way to make this journey under some form of G, as well as give the travelers enough cubic volume to maintain reasonable mental and emotional health. How it looks is unfortunately almost as important as the actual deed itself.
Raise my taxes if that is what it takes. Show me where to donate. But, please let's not do this on a shoestring. Sending a phone booth that smells like a locker room to Mars will not get a LEO Hyatt Regency built anytime soon. And make no mistake, we need that Hyatt... as well as US Steel, Dow Chemical, etc. I want 100 boosters a year rolling off the lines. Economies of scale.
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Thanks for your attention. Show me where to send a check.
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#184 by enkarha on 07 Dec, 2014 06:36
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The media aren't exactly careful with the way they use words. Plenty of architectures do leave the capsule in LEO. Some take the capsule out to a Lagrange point, and take it from there. This is probably a better way to do it, but there are things that Orion can do all by itself, especially in terms of navigation, communications, RCS, &c. which are expected of a command/service module. It works much better for lunar missions than Martian ones. In any case, Orion's on-space time specification is far too low for it to function as a Mars anything without modifications.
Also, even if a Mars transfer vehicle was built in LEO, it would not be at the ISS, which is not designed for such activity. -
#185 by guckyfan on 07 Dec, 2014 07:01
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Greetings all.
Please forgive my ignorance, but I have seen numerous reports stating Orion is the capsule that will go to Mars and Back. The latest launch was to test the heat shield for very high speed re-entry?
Why?
How is it more efficient to take an Earth re-entry vehicle to Mars and Back?
I was under the impression that that the mission would be assembled at ISS. Launched from ISS. Recovered to ISS.
Leave the ride home in LEO.
If you leave the ride home in LEO then you need to brake into LEO instead of direct reentry. That takes a LOT of delta-v. Much easier to come in directly.
Using electric propulsion changes the equation though. But that brings its own set of brandnew problems.
The other alternative is leaving from and/or returning to some earth-moon L point. But that increases mission complexity also.
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#186 by pagheca on 07 Dec, 2014 08:19
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The other alternative is leaving from and/or returning to some earth-moon L point. But that increases mission complexity also.
Do someone knows exactly why aerobraking a la MRO is not a viable option?
Too much time to ~ circularize the orbit that, in turn, would require more resources on board, so that as the technology allows it, it's better to build an high-performance shield?
Or maybe because is a risky operation open for disaster? -
#187 by treddie on 07 Dec, 2014 09:35
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Quote
I am sure that this has been asked before but why was Orion black (and not white)?
The black parts are tiles like on the Space Shuttle. -
#188 by guckyfan on 07 Dec, 2014 09:38
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Do someone knows exactly why aerobraking a la MRO is not a viable option?
Too much time to ~ circularize the orbit that, in turn, would require more resources on board, so that as the technology allows it, it's better to build an high-performance shield?
Or maybe because is a risky operation open for disaster?
I just looked up MRO in Wikipedia. It is as I expected. The arrival speed was quite low. Arrival at earth will be much faster. Then MRO was braked into an elliptical orbit that was circularized by aerobraking.
Doing that at earth will require much higher delta-v expended for capture. Then a lot of time for aerobraking with many passes through the vanAllen Belt. Or you build a vehicle that is designed for aerocapture with aerodynamic shape and a massive heatshield. But then you can land it back on earth. Why brake into LEO? It would require a much larger effort than MRO aerobraking that was done slowly, not requiring strict aerodynamic shape, just protecting some instruments.
Edit: fixed quote -
#189 by I14R10 on 07 Dec, 2014 09:58
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Why didn't they use tiles on main heat shield?
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#190 by pagheca on 07 Dec, 2014 10:22
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right, Guckyfan. However, MRO wasn't designed for a real re-entry.
Also, I wonder if there are limits for actual aerobraking. I mean: given a speed, an angle, a planet atmosphere, which are the limits for aerobraking efficiency? It is not completely intuitive that you cannot aerobrake in such a way that the system directly aims to a given trajectory.
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#191 by ncb1397 on 07 Dec, 2014 10:50
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To me, it makes the most sense to have the MTV seperate from the crew return vehicle where the MTV misses earth and the crew return vehicle intersects it. That way, the MTV can spend all the time it needs to do an efficient manuever with mass efficient propulsion to get captured into some orbit in the Earth-Moon system without worrying about extending the life support endurance to encompass the manuever. The MTV can also do far more daring or experimental manuevers like aerocapture when unmanned. Having a more capable return capsule with some independant life support capabilities means the two vehicles can seperate earlier giving the MTV some more time to get manuevered into an optimal trajectory.
I'm of the opinion that any NASA Mars architecture will have 2 crew return vehicles for redundancy in case one gets damaged or malfunctions. During the Apollo 13 mishap, there was worry that the heatshield was damaged in the explosion. If the Mars crew is 4, then the 2 orions can act as the private quarters for the crew with them rotating every 12 hours - 2 shifts with 2 people assigned to each shift. Beyond that, having two lifeboats will extend the life support endurance of the lifeboats considerably.
In addition, the MPCV could operate in the Mars/Phobos/Diemos system on its own equivalent to how it does Cislunar missions more or less independantly. -
#192 by guckyfan on 07 Dec, 2014 11:43
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right, Guckyfan. However, MRO wasn't designed for a real re-entry.
Also, I wonder if there are limits for actual aerobraking. I mean: given a speed, an angle, a planet atmosphere, which are the limits for aerobraking efficiency? It is not completely intuitive that you cannot aerobrake in such a way that the system directly aims to a given trajectory.
All true. And I did mention all of it in my post. At least I intended to, maybe I was not clear enough. My point is that when you design a vehicle capable of that you can very likely go just one step further and land it directly instead of going to LEO. MCT!
The heatshield will have to take more for landing though. A lot more, another 8km/s to brake.
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#193 by psloss on 07 Dec, 2014 11:50
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Any idea when USS Achorage and USNS Salvor will return to port? Any photos of the return?
The current schedule is arrival in San Diego on Monday. A media event is planned there. -
#194 by newpylong on 07 Dec, 2014 15:27
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Why didn't they use tiles on main heat shield?
The material is not designed to withstand leading edge reentry at those speeds, only secondary structures. -
#195 by Mapperuo on 07 Dec, 2014 16:02
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Was just peaking at this photo (attached). What are the four satellite looking dishes for on the balconys of the MST? Im assuming they are microwave transmissions to a ground station rather than to a satellite in the sky? If so, won't they fail to work during the launch due to exhaust obstructions and vibrations?
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#196 by Jim on 07 Dec, 2014 20:48
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Was just peaking at this photo (attached). What are the four satellite looking dishes for on the balconys of the MST? Im assuming they are microwave transmissions to a ground station rather than to a satellite in the sky? If so, won't they fail to work during the launch due to exhaust obstructions and vibrations?
They are only used when the vehicle is covered by the MST. They aren't used when the MST is rolled back -
#197 by Ike17055 on 07 Dec, 2014 21:44
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Ok. I have seen several views in the photos of a great display model of the orion/ delta IV stack ( yes, including Elmo holding it, i think.) Is this model available somewhere, or a custom build for the NASA pr effort surrounding this launch? This is the most handsome space vehicle i have seen in a long time.
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#198 by mike robel on 07 Dec, 2014 22:12
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Real Space Models makes one for 80.00, but you have to build it yourself. He will soon have one that features the 2nd stage, the Orion Capsule (not just the ballistic cover and LES), etc.
http://realspacemodels.com/cgi-bin/checkitout/checkitout.cgi?realspacSTORE:CKIE:prod144D-IVEFT+
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#199 by rayleighscatter on 07 Dec, 2014 22:37
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Ok. I have seen several views in the photos of a great display model of the orion/ delta IV stack ( yes, including Elmo holding it, i think.) Is this model available somewhere, or a custom build for the NASA pr effort surrounding this launch? This is the most handsome space vehicle i have seen in a long time.
ULA is selling one.
http://www.ulalaunchstore.com/120th-scale-delta-iv-heavy-with-orion-capsule/
