francoflier From France, joined Oct 2001, 3513 posts, RR: 11 Posted (4 months 4 weeks 1 day 1 hour ago) and read 3665 times:
The ESA has painted a fairly clear picture of what the next gen Ariane launcher is set to look like.
Ariane 6 is destined to replace Ariane 5 circa 2021 and interestingly, its design aims at a simpler, cheaper rocket with a payload to orbit capability similar to that of the current Arianespace workhorse.
The most interesting design choice is that of the full solid propellant 1st and 2nd stages.
Exit the Vulcain engine, enter 3 solid propellant boosters, closely based on that of the smaller Vega launcher, all in an effort to cut cost. They're also going back to a 3 stages setup, with the 2nd stage also going solid. The third stage (payload container) retains a reignitable liquid propellant engine, for obvious reasons.
Ariane is now becoming, more than ever, a 'light the fuse, step back and enjoy the show' rocket. I like the 'back to basics' approach, but I will miss the beautiful (and beautifully complex) liquid fuel engines. I guess throttling isn't a dire necessity anymore?
I'm not up to date on the issue, but I wonder if there is any other commercial launcher out there that relies so much on solid propellant?
rwessel From United States of America, joined Jan 2007, 2135 posts, RR: 2 Reply 1, posted (4 months 4 weeks 16 hours ago) and read 3591 times:
Quoting francoflier (Thread starter): I'm not up to date on the issue, but I wonder if there is any other commercial launcher out there that relies so much on solid propellant?
The Titan IIIC/IIID/IIIE/34D/4 did lift off purely on the solid boosters, and started the liquid core stage during the flight. The Japanese Mus were solids, but are now also retired. Orbital Sciences has several (Minotaur, Pegasus, and Taurus). The Israeli Shavits (although they’ve not done any commercial work). There are several others. A list:
While different techniques are possible, a gimballing nozzle is pretty common. Vanes in the exhaust stream have been done, as well as separate attitude control thrusters. While I've not actual information on what Ariane is planning, given the size I'll be surprised if it isn't a gimballing nozzle.
rwessel From United States of America, joined Jan 2007, 2135 posts, RR: 2 Reply 3, posted (4 months 3 weeks 6 days 20 hours ago) and read 3328 times:
Quoting francoflier (Reply 2): How about thrust control? Thrust pattern can be pre programmed, but is there a need for ad hoc throttling during launch?
While there are some methods for variably throttling a solid, none are pretty, although variable lateral vents can work to a degree.
But pretty much no. You can fiddle the thrust profile by shaping the fuel in various ways, and mostly it's left at that. You can add some fiddle by flying a non-optimal flight path (one trivial example is that you could fly a bit of an S-curve to scrub off some excess energy), but usually it's mostly left to a liquid upper stage to get rid of any accumulated error. And ballast.