14 thoughts on “Developing Space”

  1. Do you suppose SpaceX will have all their launches from Canaveral held up by the Air Force?

  3. I also think he has a few too many zeros on the number of solar system asteroids 1 km or greater in diameter. 10^15 is just not credible.

  4. Ken, the only time anyone in the 45th Space Wing moves fast is when they are moving from one air conditioner to another! I expect they will do everything in their power to slow and frustrate SpaceX. It’s all done in the name of safety – of course. Some safety – good, don’t blow up the neighbours etc. Lot of safety is a bit nonsensical and mainly designed to be obstructive.

    I finally gave up trying to deal with them from a commercial standpoint. To much effort for very little gain.

    Nemo, the inaccuracies in the Constellation stuff do not necessarily invalidate the argument.

    For the record SFO has been preaching a very similar song since we started in 1992.

  5. MfK, if you’re just talking about the main asteroid belt, then yeah, 6 zeros too many. If we’re including all objects 1km or bigger in the entire solar system (indluding the Kuiper belt and Oort cloud) then a quadrillion is about right.

  7. Whenever presenting numbers one should have references handy. Similarly when refuting numbers. It’d be great if people were to bother at least *trying* to have a fact based discussion.

  8. The Wikipedia asteroid belt article says you’ve got nine or ten zeros too many, Ed. It gives a figure of 700,000 to 1.7 million 1km or larger asteroids in the main belt and cites an Astronomical Journal article as source material. It also says the total mass of the main belt is roughly 4% that of the Moon.

  9. I love the way Ed has to reach for “bus” and “bus station” because “shuttle” and “space station” have been so polluted by NASA activities. Bravo.

  10. Nemo, if you post a comment correcting my inaccuracies (here or at robot guy) I will be glad to update that post.

    Thanks, Ed.

    The Ares-1 would consist of a single shuttle solid rocket booster with an external tank mounted on top, and then the Orion crew capsule mounted on top of that.

    Not an external tank, but a second stage. This sounds like a nitpick but “external tank” can be confused with “External Tank” and you did properly use “second stage” in reference to the Ares V below.

    The Ares-V would use the existing solid rocket boosters and external tank in their side-by-side configuration, with a second stage mounted on top.

    Not the existing SRBs, but five-segment SRBs.

    These would both use new engines mounted on the bottom of the external tank, but other than that, all off-the-shelf components.

    Ares I would have used an SSME modified for airstart, while Ares V would have used existing SSMEs.

    Once NASA actually started crunching the numbers on the design, it became clear that the existing solid rocket motor wasn’t up to the job of being a first stage for the rest of the rocket. It needed to be bigger by another section, going from four to five solid rocket sections. This meant that the burn rate had to be adjusted as well, and thus a new fuel grain mixture – basically, an entirely new solid rocket motor, sharing only superficial visual commonality with existing hardware.

    Not true. Ares V had 5-segment SRBs from the beginning and it was already known that this would require new propellant grain. Ares I went to a 5-seg not because NASA “actually started crunching numbers” (that is insulting and you should know better), but because NASA changed the second stage engine from an SSME to a J-2X. This was because the SSME airstart modifications were going to be more expensive than anticipated, and because the SSME itself would be expensive for an expendable engine. Because the Ares V already used a J-2 derivative in the second stage, the decision was made to eliminate SSME from the design and go with the J-2X across the board. (Likewise, the Ares V core stage went with the existing RS-68, which is cheaper – albeit less efficient – than the SSME). So this move resulted in standardization of the 5-segment SRB across the family, but unfortunately put 5-seg in the critical path for Ares I, which moved the budget “hump” for 5-seg development earlier. (Rock and a hard place, for sure, since the alternative would have been to up the budget hump for the airstart SSME).

    With a single motor attached at a single point at the bottom of the Ares-1, the vibrations from spikes in thrust would become so intense that the astronauts aboard would be shaken to death, assuming control was possible at all.

    This was exaggerated even at the time, and Ares I-X data shows that the software models overpredicted thrust oscillation.

    Now the solid rocket booster isn’t strong enough to lift it all, and we need another half a section added to the booster… back to the drawing board.

    Untrue. Ares I is still 5-seg. Ares V went to 5.5 seg, but that was not because of TO, but because of the reduced efficiency of the RS-68 compared to the SSME.

    The Orion capsule went from a capacity of seven astronauts, to five, to three.

    Untrue. It went from six to four.

  11. The reason I used “bus” and “bus station” was that I wanted to describe the function being performed. I have made several very long bus trips across Canada and the US, and I had the Greyhound bus stations in mind. But, if you want to credit me with more cleverness than I intended, that’s ok too.

  12. Dick, I wasn’t just looking at the asteroid belt, I’m including the Kuiper belt and Oort cloud as part of the solar system.

    Upon reflection it would have been more accurate to say a Zillion.

  13. Nemo:

    This was exaggerated even at the time, and Ares I-X data shows that the software models overpredicted thrust oscillation.

    I have to disagree with this. The Ares 1x did not use the new and still not flight-tested SRB and had a dummy second stage, which is why I called it a Potemkin rocket. Other than that, I made corrections based on your suggestions.

  14. I have to disagree with this. The Ares 1x did not use the new and still not flight-tested SRB and had a dummy second stage, which is why I called it a Potemkin rocket.

    Incorrect. The software model was correctly configured for the as-flown Ares I-X configuration and still overpredicted thrust oscillation. Therefore the model has been invalidated, and its Chicken Little predictions for the Ares I configuration should be treated skeptically.

    Which brings me back to my main point: you completely missed the boat by focusing on the technical problems with the Ares development program. While problems exist, they are no more than is to be expected for a new LV development program. What you should have focused on is that the LV architecture itself is ill-conceived. Ares I is a wasteful duplication of capabilities of existing 20-ton-to-LEO ELVs, and Ares V is so large it will require reconstruction of much of the LC-39 facility in order to accommodate it.

Comments are closed.