Looks interesting, wish Gary and all the other team members good luck!
Quote from: meekGee on 01/21/2022 04:29 amWhat I don't understand is what does SSTO buy you over a streamlined TSTO system that's compromised of two independent rapidly reusable vehicles.I mean by definition you'll be lugging your first stage to orbit and then re-entering it.Not only will it be more complex and expensive, but you also won't have it back in 20 minutes to launch again..I see the allure when compared with a traditional "pieces fall off" type rocket, but I just don't see the motivation at the present time.1. The ability to operate from a runway, even if you have to drag a launch sled along with you to do it, dramatically simplifies your ground handling and infrastructure. It also gives you more flexibility when deciding where to launch from.2. Being an SSTO, no time or money (money is the far more important part) has to be spent between flights on vehicle integration, only payload integration. Yes, stage integration has historically been far less efficient than it could be. That doesn't change the fact that no integration is still faster and cheaper, particularly since that means you don't need to build and/or maintain and/or travel-to the facilities needed for stage integration. (Unless you decided to use a launch sled, in which case I guess reintegration with the sled is basically stage integration. I really don't like the sled.)3. Even SpaceX isn't seriously consider launching the same vehicle more than once a day, so having to wait at least 90 minutes to get the vehicle back is hardly an issue.4. This is in some ways more of an idle thought than a point. I would also think that a reusable TSTO should be inherently simpler than an SSTO. That said, the main example we have of a RTSTO design is Starship, which is using the most complicated rocket engine ever developed. Only time will tell, but it may be the most teams designing RTSTOs willingly give up their simplicity advantage in favor of further boosting their performance advantage.
What I don't understand is what does SSTO buy you over a streamlined TSTO system that's compromised of two independent rapidly reusable vehicles.I mean by definition you'll be lugging your first stage to orbit and then re-entering it.Not only will it be more complex and expensive, but you also won't have it back in 20 minutes to launch again..I see the allure when compared with a traditional "pieces fall off" type rocket, but I just don't see the motivation at the present time.
Quote from: Robotbeat on 01/20/2022 01:10 pm(Although we don’t know what they’re using… if it’s hydrolox like X-33, then they will struggle. It’s one of the worst SSTO propellants to use because of its low density.)I'd caveat that statement re: low density of hydrolox with "when used at normal mixture ratios in normal rocket engines". With LOX-rich TAN, you could theoretically make a stage O/F ratio of 12-18:1 work (instead of the traditional 4-6:1), which would help bulk density a ton, at the cost of lower Isp during the boost phase (which does help lower gravity losses though).I do agree though that pure LOX/LH2 at traditional mixture ratios has crappier bulk density than you'd want for an SSTO. When Aerojet did their TAN papers, they also looked at tri-propellant TAN -- where the main chamber was LOX/LH2, and the TAN injection was LOX/Kero. IIRC, they showed that that tripropellant approach actually closed way better than either pure LOX/Kero or pure LOX/LH2 for an SSTO designs -- high thrust and high bulk density for the start, high Isp for the end, and overall a great T/W ratio on the engines in booster mode (especially compared to typical LOX/LH2 engines).Given that Radian hasn't publicly stated what their engines are using, it's possible they could be doing something clever/unusual like this. Though I kind of think they would've said so if they were, because that would make the whole concept seem more plausible.~Jon
(Although we don’t know what they’re using… if it’s hydrolox like X-33, then they will struggle. It’s one of the worst SSTO propellants to use because of its low density.)
TAV concept had a jet sled launch...
Quote from: jongoff on 01/20/2022 10:07 pmQuote from: Robotbeat on 01/20/2022 01:10 pm(Although we don’t know what they’re using… if it’s hydrolox like X-33, then they will struggle. It’s one of the worst SSTO propellants to use because of its low density.)I'd caveat that statement re: low density of hydrolox with "when used at normal mixture ratios in normal rocket engines". With LOX-rich TAN, you could theoretically make a stage O/F ratio of 12-18:1 work (instead of the traditional 4-6:1), which would help bulk density a ton, at the cost of lower Isp during the boost phase (which does help lower gravity losses though).I do agree though that pure LOX/LH2 at traditional mixture ratios has crappier bulk density than you'd want for an SSTO. When Aerojet did their TAN papers, they also looked at tri-propellant TAN -- where the main chamber was LOX/LH2, and the TAN injection was LOX/Kero. IIRC, they showed that that tripropellant approach actually closed way better than either pure LOX/Kero or pure LOX/LH2 for an SSTO designs -- high thrust and high bulk density for the start, high Isp for the end, and overall a great T/W ratio on the engines in booster mode (especially compared to typical LOX/LH2 engines).Given that Radian hasn't publicly stated what their engines are using, it's possible they could be doing something clever/unusual like this. Though I kind of think they would've said so if they were, because that would make the whole concept seem more plausible.~JonMaybe they were being guarded while TAN was going off-patent? The basic TAN patent is now open, but were the tripropellant modes free and clear then?
As john smith 19 pointed out before, this is quite similar to Boeing RASV, which also uses a sled for takeoff.Source: https://apps.dtic.mil/sti/citations/ADB216503
Would they win something if they combined it with a ramjet/scramjet engine - also on the way back? Also, why not make two variants, one unmanned cargo version and one manned. Starting with a manned version makes it more complicated and shaves off the margins.
Also, uncrewed launch is kind of a saturated market right now.Uncrewed launch with vehicles flying* or with hardware and within a couple years of launch:SpaceX (Falcon 9, Heavy, Starship)*Antares (NG)*ULA (Atlas, Delta, Vulcan)*Blue Origin (new Glenn)*ishRocketlab (electron, Neutron)*VirginOrbit*Astra*Firefly*ishABLRelativityand others (SLS? launcher?)That’s just in the US.Crewed orbital launch, currently flying:SpaceX. That’s it.In the future:Orion and Boeing are not far, but they’ll likely be too expensive for real commercial uses.Maybe Dream Chaser.So the list of orbital crewed launch is much smaller. And the revenue for crewed launch might be more than the whole smallsat launcher industry, so I don’t think it’s something to ignore.Enables satellite servicing and space tourism markets while also giving a possibility of those lucrative NASA crew contracts, which could be over a billion dollars per year (that’s like hundreds of micro/smallsat launches’ worth).
@JSThey may have other IP that is not mentioned in the patent, as when a patent is filed, they have 16 years to exercise it. So keeping it as a trade secret may be a better strategy depending on how long time they estimate it will take to develop. They have raised some money, so external parties have likely done some due diligence on the concept.
Did the shuttle have an escape pod?
If it's a plane, can they then forego the escape capsule as they can glide back to earth unpowered, unlike a rocket?
You assumed they got to 200 km/h with the sled? Would it not be possible to move that to 400 km/h and would that make any difference?
They are working on the marginals I believe and since they have raised that kind of money and attracted astronauts they must have found a way where the marginals are enough in their favor. If it was easy everyone would do it.