Talk:Scaled Composites Tier One
technical info
I came across a newsgroup post to sci.space.tech which contains a great amount of technical info, gleaned from a recent presentation Rutan did. I'm not sure how reliable the information is, though, or if the info is considered public (though I guess it's out of the bag now, since it's been posted to usenet). Particularly noteworthy are details regarding the ISP and total impulse of the engine. --NeuronExMachina 22:03, 15 Aug 2004 (UTC)
- Now incorporated some of that into the article. 81.168.80.170 20:04, 11 Sep 2004 (UTC)
The article currently states that the dry mass is 2.0 Mg (if it's given with 2 digits accuracy it should be 1.9 Mg if you calculate it from gross mass and fuel). If you google for it you'll find more sites stating that the dry mass is only 1.2 Mg. Indeed, after a quick search I can't find any other site which would confirm the 1.9 or 2.0 Mg dry mass. 193.171.121.30 06:51, 14 Sep 2004 (UTC)
- The mass figures are from the newsgroup article noted above. They may well be inaccurate; please post links to more reliable sources of information. The 1.9 Mg vs 2.0 Mg thing comes from the source document having specified masses in pounds: each figure given is a correctly rounded conversion from pounds, and the result is that the sum that worked in pounds doesn't come out right in converted form. 81.168.80.170 20:21, 26 Sep 2004 (UTC)
- Afterthought: I've now tagged the mass data as {{dubious}}. 81.168.80.170 21:56, 27 Sep 2004 (UTC)
The article states that the engine was updated between the flights 15 and 16, but I seem to recall that Burt Rutan stated that this is not the case and they just planned a longer burn. Maybe they took delivery of the upgraded engine but didn't use it ? --195.137.80.174 10:31, 30 Sep 2004 (UTC)
comparison with Shuttle reentry
- I'd like to respond to what User:81.168.80.170 wrote about my recent edits to Tier One:
I ended up reversing all three of your substantive edits to Tier One:
- You changed a link from pilot (spaceflight) to pilot. The original was correct, despite the linked article not existing yet; pilot is a disambiguation page, and pilot (spaceflight) is one of the articles it points at. I've created a substub there to avoid future confusion, but this kind of thing is common. You should avoid making links more ambiguous than they were to start with, and remember that a link to a non-existent article is not broken per se.
- You changed "Mg" to "tonne". The article consistently uses SI units, so "Mg" is appropriate.
- Without mention in the edit summary, you added some HTML comments that appear to cast doubt on the NPOVness of the comparison between the reentry modes of SpaceShipOne and the Space Shuttle. If you have such doubts, please raise them on Talk:Tier One, or improve the text yourself.
195.167.169.36 15:30, 27 Sep 2004 (UTC)
All fair comments, and first I must say I found the whole article fascinating and very informative.
- Now I changed pilot (spaceflight) because it linked nowhere and I thought a link to the disambig would be better as it gives the user something rather than nothing, but it's good that "pilot (spaceflight)" now exists.
- I changed Mg because it looks really strange! SI it may be but other rocketry sites and technical documents I've seen use the SI unit kg, so 2,000 kg for example would be better than tonne, which despite being a non-SI unit is accepted by SI as a 'SI-compatible' special name for megagram and still useful. ESA and Nasa both appear to use kg. Until this article I'd never seen Mg in documents. I now think 2000 kg would be better though.
- My NPOV concerns were too mild to make much of a fuss over, but it struck me that the far safer claim (which I agree with within the velocity range considered, 3-4 Mach I think) needs two changes: which reports show that it is safer and limitation of the comparison should be up front.
How about: (Aerodynamic studies show that) This is a safer attitude in which to glide at the 3-4 Mach entry velocity than the comparable attitude taken by the Space Shuttle at that same velocity. The Shuttle must be actively steered to maintain a stable glide attitude, however the Shuttle starts reentry at much higher speed than SpaceShipOne.
Not the best prose, maybe the last sentence could be:
The Shuttle must be actively steered to maintain a stable glide attitude, however the Shuttle's design was constrained by the far higher energies that it contends with at its higher reentry velocity.
Now that reads too defensive, but my (admittedly weak) point is that it's an unfair comparison as the conditions each craft contends with are very different. -Wikibob | Talk 19:48, 2004 Sep 27 (UTC)
You're definitely onto something here, and thanks for working on this. I recall being slightly dubious about how to word this comparison when I wrote it, because it's neither precisely a fair comparison nor precisely unfair. Issues to consider on fairness (shamelessly repeating those already stated):
- the Shuttle reenters at far higher speed than SpaceShipOne (hence unfair comparison)
- the comparison holds when restricted only to similar speeds (hence fair comparison)
- even when considering similar speeds, the Shuttle design is intended for much higher speeds (hence unfair comparison)
- the Shuttle didn't have to be designed for hypersonic gliding in the first place; it could have done a belly-first ballistic entry if the Air Force hadn't demanded cross-track capacity for a polar mission (hence fair comparison?)
- even if it hadn't been designed for hypersonic gliding, the Shuttle still wouldn't have been as stable a glider as SpaceShipOne (hence a fair but rather hypothetical comparison)
Rather than attempt to explain all of that in the article, I've changed it to just note that there is the unfairness that you point out. Here's the new text I've put in place:
- This feathered reentry mode is inherently far safer than the behaviour at similar speeds of the only comparable craft previously built, the Space Shuttle. The Shuttle undergoes enormous aerodynamic stresses and must be precisely steered in order to remain in a stable glide. (Although this is an interesting comparison of behaviour, it is not an entirely fair comparison of design concepts: the Shuttle starts reentry at much higher speed than SpaceShipOne, and so has some very different requirements.)
Any advance on this? 81.168.80.170 22:18, 27 Sep 2004 (UTC)
names
Do the names "SpaceShipOne" and "White Knight" refer to the aircraft designs or to the aircraft themselves? In each case we have so far a single instance of the design, and in popular usage we speak of "SpaceShipOne rolling to the left" and so on. If a second instance of Scaled model 316 were built, would we now have two SpaceShipOnes, or would we have SpaceShipOne and an identical spacecraft with a different name? 195.167.169.36 10:09, 28 Sep 2004 (UTC)
- I dunno, in this case, probably both. It seems that at least SS1/Model 316 is probably a one-off, as they have elected for a larger model for future production for Virgin. As for White Knight, that's tougher to guess, since they're going to use it for other projects (X-37), it seems. But I doubt it has the oomph to loft the Virgin craft. -Joseph (Talk) 10:52, 2004 Sep 28 (UTC)
SI units
Not sure where this Mg stuff is from. See the SI page here for more info, but the correct SI units for mass are Kg. Mg is just not used, please see the SI page. I will avoid "tonne" and go for Kg in keeping with the rest of the article.
If you don't agree with this, please take a vote here before reverting my changes. Mat-C 23:29, 29 Sep 2004 (UTC)
- You appear to misunderstand SI. SI provides not only a base unit for each quantity (metre for length, kilogram for mass, and so on) but also a set of related units for the same quantities at different orders of magnitude. When discussing lengths above 1,000 metres, it is convenient to speak in kilometres: 1 kilometre = 1,000 metres (1 km = 1000 m). Both the metre and the kilometre are SI units, though the metre has the distinction of being the SI base unit. Similarly, when discussing masses above 1,000 kilograms it is convenient to speak in megagrams: 1 megagram = 1,000 kilograms (1 Mg = 1000 kg). Both the kilogram and the megagram are SI units. "Kg" doesn't mean anything, except possibly "kelvin gram": "K" is the SI symbol for kelvin, a unit of temperature, whereas what you're looking for there is the symbol prefix "k", referring to the SI prefix "kilo-", a multiplier of 1000.
- The rest of the article is consistent with the engineering style of SI usage: all the quantities are stated with appropriate SI units such that the numbers are greater than or equal to 1 and less than 1000 and the SI prefixes are all powers of 1000. This is what the SI prefixes, at intervals of multiples of 1000, are designed for. If you wish to deviate from that scheme then you had better provide a good reason for it. There are potentially good reasons to do this, which I'll happily debate if someone proposes them. Being unfamiliar with the SI unit of the megagram, particularly when an article on it is linked from the unit symbol, does not qualify in a technical article.
- Please supply revised opinions when you understand SI. This is not an attempt to be dismissive, by the way: SI is not difficult to understand, and Wikipedia itself provides sufficient material for you to learn the mechanics (though not every nuance) of what's going on. I really do intend for you to learn SI and think meaningfully about this article in the light of the knowledge you acquire. As for a vote, that does not appear to be the Wikipedia way. I'll look for a consensus on this talk page. 81.168.80.170 00:59, 30 Sep 2004 (UTC)