Talk:Tier One

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[edit] 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)
I don't know how reliable this source is, but they're talking about a dry weight of 1200 kg e.g. in Encyclopedia Astronautica[1]. It may well be that the total mass of 3600 kg is wrong because the total oxidizer+propellant is 3600 pounds and someone may have confused the numbers. 193.171.121.30 15:03, 2 Oct 2004 (UTC)
That site's pretty reliable, I'd say. -Joseph (Talk) 16:23, 2004 Oct 2 (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)

[edit] 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)

It's better as the comparison is now at similar speeds. Meanwhile, while looking for better mass figures I found this database but it doesn't (yet) include SpaceshipOne. -Wikibob | Talk 23:51, 2004 Sep 27 (UTC)

[edit] Belly-Flop reentry

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?)

Actually, that's not quite true. The belly-first reentry was a feature of the SSTO designs. By the time NASA redesigned the Shuttle in an attempt to bring the USAF onboard, the design has already shifted to TAS. (Thrust Augmented Shuttle - essentially the design that was built.) The development costs of the SSTO versions were believed to be very high (with good reason - it would have been larger than a C-5A!), and thus the shift to the (seemingly) simpler and cheaper TAS design.

Even so, the belly-first position had some significant problems with heat flow around the wing roots and the horizontal stabilizer. It also faced the non-trival aerodynamic problem of shifting from belly-first airflow to conventional (nose-first) airflow. Additionally the SSTO versions would have required an untried method of building "hot-structure" skin in order to survive re-entry at all. Lastly, the SSTO designs still would have faced high-sonic conditions during both launch and reentry.

Despite the mythology that has arisen around them, the SSTO versions were nothing more than paper - they never were mature designs. There is no evidence to believe that solving their problems would have resulted in a vehicle significantly cheaper that the Shuttle we have now. Elde 08:19, 7 Apr 2005 (UTC)

[edit] 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)

[edit] 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.
I think you are missing an important point here. The SI system was developed as an extension of the MKS system, which superseded the earlier CGS system, whose centimetre and gram base units of were optimised for laboratory work an were too small for most commercial/engineering/industrial use. The MKS and later SI base unit of mass is the international prototype kilogram, a platinum-iridium cylinder kept at the Bureau International des Poids et Mesures, near Paris.
Confusingly, the SI base unit for mass was not given a new base unit name, but instead was named the kilogram, suggesting that it was the same mass as 1000 grams in CGS, which is untrue, because the gram in the CGS system was defined as the mass of pure water at maximum density that would fill a cube whose edges are each 1 cm. In the SI system the gram is defined simply as 0.001 kg; therefore, although it is the "linguistic" base unit of the naming scheme for units of mass, it is not the base unit of mass itself.
In countries where the SI system is in everyday use, the use of Mg to refer to a mass in the range of thousands of kg appears contorted and archaic, as it (a) suggests that the base unit is being pointlessly divided by one thousand to be then multiplied by one million, and (b) suggests that the author may be thinking/measuring/writing in the now obsolescent CGS system, with its (once slightly) different base unit definitions.
In engineering usage, when scientific notation is not being used, masses in this range are almost always specified either as kg figures in the thousands range, or as (metric) tonnes. In practice, the more the mass exceeds 1,000 kg, the higher the probability that it will be expressed as tonnes. Also, there is an (illogical) bias towards using kg when it is desired to de-emphasise the mass/weight, and a tendency to use "tonnes" to emphasise mass/weight. iolar 00:44, 12 Oct 2004 (UTC)
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)
I think using Mg is just irritating, not to mention pretentious. Stick to kg×103. And don't be so preachy. -Joseph (Talk) 01:04, 2004 Sep 30 (UTC)
In places that use SI, 1000kg is usually called a tonne, or if you really like to mispell things, a metric ton. There are common names for units in the metric system that aren't based on the base units. Even kilogram, though a base unit in SI is not the base of the mass scale, which is infact, the gram. (hence the kilo- prefix). Common names widely used are tonne, hectare, etc... ; instead of calling it a Mg, which looks too much like an element, try using 1000kg or 1 tonne. Try to find a place in the world that actually would use Mg commonly. 132.205.64.11 16:34, 4 Oct 2004 (UTC)
I don't like to gang up against Mg, but as far as I've seen in technical documents (ESA, Arianespace, Eurocontrol) kg are used for masses, even those over 1000. Tonnes are used in public and customer-related documents (ESA publicity). Excluding myself, I asked a Belgian engineer who uses SI units and hhe told me they use kg in technical documents. He knew what Mg was but was adamant it would never be used. However I have corrected the spelling of Kg to kg. -Wikibob | Talk 13:14, 2004 Sep 30 (UTC)

[edit] Ingredients

The parts of the craft that experience the greatest heating, such as the leading edges of the wings, have about 6.5 kg of ablative thermal protection material applied. The main ingredient of this material was accidentally leaked to Air and Space.

What is the main ingredient? --[[User:Eequor|η♀υωρ]] 01:22, 5 Oct 2004 (UTC)

[edit] Passengers on SpaceShipOne

There has been some to-ing and fro-ing in this article about a) whether or not SS1 will carry paying passengers, and b) the fee for that.

I would humbly suggest that this is all speculation. There are no published plans to take paying passengers on SS1. There are plans to fly the craft regularly to test it further, and i think it would be safe to speculate that there will be some passengers - however none of us know who these will be and whether or not they will pay for it. My own personal feeling is that the most likely passengers would be Burt and other Scaled personnel. Paul Allen said recently that he would like a seat on the first Virgin flight... no mention of going up in SS1.

The X-Prize foundation (Anousheh Ansari, etc.) have, as part of their deal with the teams, a number of allocated seats on 'early commercial flights'. In the case of SS1, the first commercial use of its technology will be Virgin Galactic.

On the fee; any adjective applied to a fee e.g. 'exorbitant' is simply a point of view, and should be marked as such. Tito didn't think that $20m was exoribitant, although I do... so its exorbitancy is simply my POV... I think a similar POV statement should apply to the use of the term in this article.

I'd like to replace the aspects of the article to be more reflective of the fact that there is much speculation about flights on SS1, but that the first commercial flights will be on Virgin Galactic, if anyone doesn't object too strongly?

Cheers, PoleyDee

If I understand correctly, under current US laws, SpaceShipOne can't legally carry paying passengers. --NeuronExMachina 02:20, 11 Oct 2004 (UTC)
Good point. When Virgin Galactic launched, they did talk a lot about 'subject to appropriate government permits'. I guess that answers that one then! PoleyDee 16 Oct 2004


[edit] Virgin Galactic

I think it is important that, as this page is off the beaten track, any info/news on Virgin Galactic should be kept out, as the company will be changing quickly with the climate, and there is a dedicated page for information on VG. The whole export restriction thing is just a ploy to keep high tech buisness withing the US (and it works; the Virgin space fleet will now be built in america, whatever Branson's original plan might have been)

Whatever. The export restrictions issue was nullified two days ago. [2] Joseph/N328KF (Talk) 16:19:21, 2005-08-17 (UTC)

[edit] More details on flight controls

FYI, this newsgroup posting has many more details about the flight controls, from a talk which Mike Melville gave.

--NeuronExMachina 01:50, 4 Dec 2004 (UTC)

[edit] VPROTECT

This page is VPROTECTed. Why is that? I don't see anything in the history, so I guess an admin suppressed it. 132.205.15.43 04:09, 24 Dec 2004 (UTC)

On what grounds was it protected? There was no vandalism problem here. -Joseph (Talk) 04:39, 2004 Dec 24 (UTC)
Two glyphs for ya: /. -Fennec (はさばくのきつね) 04:26, 25 Dec 2004 (UTC)

[edit] Tier Two

t/Space is working with Burt Rutan's Scaled Composites for cheap flight into Orbit http://www.transformspace.com/ http://www.astronautix.com/craft/cxv.htm 81.244.170.155 13:43, 25 April 2006 (UTC)

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