Quote from: Keith Henson on 05/31/2016 10:55 pmBTW, the Skylon are expected to fly every other day. 140/month was the production rate of Skylons to keep up a million flights per year. If you rebuild them at 500 flights, it would reduce the projection rate to 70/month. The cost estimate graph mentioned in this thread gets down to $120/kg at around 100,000 flights per year. The electric propulsion (at 30,000 tons per month) add about $55/kg to the cost.These are quite an absurd numbers, really. You'd need to have a multi-planetary species to support anything remotely near that number, it's such a high number for one launch vehicle to go that we are stepping into the realm of sci-fi. It's not feasible within a lifetime of any of us.
BTW, the Skylon are expected to fly every other day. 140/month was the production rate of Skylons to keep up a million flights per year. If you rebuild them at 500 flights, it would reduce the projection rate to 70/month. The cost estimate graph mentioned in this thread gets down to $120/kg at around 100,000 flights per year. The electric propulsion (at 30,000 tons per month) add about $55/kg to the cost.
Those of you who know my ID, know I am a huge fan of the Reaction Engine chaps. Thing is I am also a huge Elon Musk fan - and he says solar powered satellites are unnecessary.
Those of you who know my ID, know I am a huge fan of the Reaction Engine chaps. Thing is I am also a huge Elon Musk fan - and he says solar powered satellites are unnecessary. Being a huge REL fan for years I picked up on that comment straight away since I know of the old REL SPS study. In this video (at 3 minutes) he says, "If anyone should be in favour of solar power satellites it should be me ... but this is completely unnecessary"
Quote from: flymetothemoon on 06/03/2016 01:52 pmThose of you who know my ID, know I am a huge fan of the Reaction Engine chaps. Thing is I am also a huge Elon Musk fan - and he says solar powered satellites are unnecessary. Being a huge REL fan for years I picked up on that comment straight away since I know of the old REL SPS study. In this video (at 3 minutes) he says, "If anyone should be in favour of solar power satellites it should be me ... but this is completely unnecessary"This is fairly old now, discussed here http://forum.nasaspaceflight.com/index.php?topic=30107.msg969044#msg969044 (Oct 2012) and more recently here http://forum.nasaspaceflight.com/index.php?topic=17902.msg1511703#msg1511703 (May 2016)If you want to compare SPS with a relatively small scale terrestrial system located in the desert of your choice then I'd agree with Musk, with the caveat that his fabled photon-to-electron-to-photon-to-electron dismissal is actually not that bad at all: space solar beats equatorial noon sun by 37%, the dc-(space)-to-microwave-to-dc-(grid) can be achieved with an efficiency of around 50%. Add in the fact that power is constant except for a few hours each equinox (compared with terrestrial day/night cycles and weather) then, on average, space solar produces about 11 times more energy than the equivalent terrestrial system.If your goal is to wean humanity off fossil fuels, then your options are limited. Take the (not-so-sunny) UK for example. Terrestrial solar farms average approximately 10W/m^2. An equivalent grid-scale rectenna would be limited only by the safe-level central peak beam intensity of 250-350W/m^2 (one-quarter to one-third noon sunlight intensity), giving an average power density of 60W/m^2 - i.e. requiring only one-sixth the land area, which could remain dual use for growing crops.Of-course if you are contemplating fully renewable energy (as opposed to sustainable energy including fission/fusion power), then almost everything other than SPS requires truly massive grid-scale storage to meet baseload requirements.Once as a civilisation we decide we can no-longer live with fossil fuels, and probably before fusion can be scaled globally, we will need Skylon, or something very much like it, to achieve the high flight rates - costs be damned!
We have not seriously explored taking the SKYLON type vehicle up to the heavy lift class but the few “fun exercises” we have done have not shown any fundamental upper limit technically but the economics go to pot. Basically making the systems as small as possible while still capturing the main market (i.e. not small sats) throws the economic burden on to more launches (where reusables score) and off development cost and acquisition cost (where reusable suffer).
http://forum.nasaspaceflight.com/index.php?topic=24621.msg735577#msg735577Quote from: HempsellWe have not seriously explored taking the SKYLON type vehicle up to the heavy lift class but the few “fun exercises” we have done have not shown any fundamental upper limit technically but the economics go to pot. Basically making the systems as small as possible while still capturing the main market (i.e. not small sats) throws the economic burden on to more launches (where reusables score) and off development cost and acquisition cost (where reusable suffer).Sounds like a yes.
Quote from: 93143 on 06/06/2016 10:16 amhttp://forum.nasaspaceflight.com/index.php?topic=24621.msg735577#msg735577Quote from: HempsellWe have not seriously explored taking the SKYLON type vehicle up to the heavy lift class but the few “fun exercises” we have done have not shown any fundamental upper limit technically but the economics go to pot. Basically making the systems as small as possible while still capturing the main market (i.e. not small sats) throws the economic burden on to more launches (where reusables score) and off development cost and acquisition cost (where reusable suffer).Sounds like a yes.jongoff makes a good argument for scaling down to like ~3 tons LEO, then using refueling and a transfer stage to put those 3 ton payloads directly to GSO. That would be about equivalent to 5 tons GTO.So I wonder if Skylon could halve the cost (and development time) if they went for a ~3 ton payload instead of 10-15.
Skylon already has a Skylon Upper Stage
Quote from: Robotbeat on 06/07/2016 08:17 pmQuote from: 93143 on 06/06/2016 10:16 amhttp://forum.nasaspaceflight.com/index.php?topic=24621.msg735577#msg735577Quote from: HempsellWe have not seriously explored taking the SKYLON type vehicle up to the heavy lift class but the few “fun exercises” we have done have not shown any fundamental upper limit technically but the economics go to pot. Basically making the systems as small as possible while still capturing the main market (i.e. not small sats) throws the economic burden on to more launches (where reusables score) and off development cost and acquisition cost (where reusable suffer).Sounds like a yes.jongoff makes a good argument for scaling down to like ~3 tons LEO, then using refueling and a transfer stage to put those 3 ton payloads directly to GSO. That would be about equivalent to 5 tons GTO.So I wonder if Skylon could halve the cost (and development time) if they went for a ~3 ton payload instead of 10-15.Where does this refuelling come from? Skylon already has a Skylon Upper Stage to handle the GTO, which like Skylon is designed to be reusable. Provided you don't hit the machinery or building limits (which impose step change costs) bigger is not that much more expensive, and hence smaller is not that much more cheaper.
Quote from: john smith 19 on 06/08/2016 12:55 amSkylon already has a Skylon Upper Stagesix year later ...... can you post a picture of this Skylon.. or at least a working air breathing rocket engine ?
Quote from: Avron on 06/08/2016 01:03 amQuote from: john smith 19 on 06/08/2016 12:55 amSkylon already has a Skylon Upper Stagesix year later ...... can you post a picture of this Skylon.. or at least a working air breathing rocket engine ?Probably could have said it less sarcastically But this really needs some progress now. If other vehicles are subject to questions, this one should be too. To me it feels like it's stuck in the mud somewhat. I'd "love it" if I could be proven wrong. Keegan-style (UK folk will get that reference).
Just saw that the USAF are expected to announce a development programmer based around the SABRE pre cooling technology later this year. Is this new information or just a continuation of the studies they have been working on together in the past?http://nextbigfuture.com/2016/06/us-air-force-research-will-develop.html