[X] My Assistant

[AscendingNode]

So I've been thinking a lot lately about the BFR (Big Fantastic Rocket) being developed for the NASA manned spaceflight program, the Ares V. And I was wondering what sort of robotic missions it would make possible that before weren't possible.

At first I was thinking you could take something like the proposed Europa Explorer mission... which launches on a Delta IV heavy and orbits Europa.... and you could take that spacecraft and put it on a bigger rocket and do things like add extra radiation shielding so it could last longer or add extra propellant so that it could orbit Callisto, Ganymede, and Europa or something like that.

But that's just an improvement to an existing concept... what about things that no one has really thought about because they've been just thinking about things that could fit on existing rockets.

Sure, we could do things like putting an armada of spacecraft on one vehicle... but that would cost a lot of money for all of the separate power systems (RTG or Solar) and avionics... and that concept could be done anyway with multiple launches of existing rockets.

But with a BFR, we could do a Cassini style mission to Neptune (i.e. get to Neptune fast and carry enough propellant to stop from a high-speed encounter and do a tour). Or we could maybe carry enough shielding to orbit Io

So, what do y'all think? How would you fly a BFR?

[dvandorn]

Actually, the Shuttle is a beast unto itself when it comes to man-rating a launch vehicle. As designed, it cannot be flown unmanned -- you would need to make several major modifications to it if you wanted to fly it unmanned, which were considered to be too expensive (and, in some cases, dangerous) to build in.

But the Shuttle is its own launch vehicle in some ways -- the main engines are integral to the manned vehicle. So you cannot actually fly any portion of a Shuttle stack unless the orbiter is manned.

So, the Shuttle flew for the first time (and has always flown) with "exception waiver" documents. The basic approach is that there are some issues, inherent in the design of the vehicle, which render it potentially unsafe -- the location of the orbiter in the stack and the inability to shut down the solid rocket boosters once ignited, among other things -- which make the vehicle impossible to man-rate. So the Shuttle flies, every single time, with signed waivers which state that the program managers and crew are willing to undertake the risks associated with the items that cannot be man-rated.

In that way, the Shuttle has never actually been man-rated.

The Ares I approach will also require a Level One waiver for the use of a solid rocket booster as its first stage, for the same reason the Shuttle requires the same waiver -- the motor, once ignited, cannot be shut down. And, in at least that one aspect, it, too, will never actually achieve the status of man-rated.

-the other Doug

[nprev]

Actually, the Shuttle is a beast unto itself when it comes to man-rating a launch vehicle. As designed, it cannot be flown unmanned -- you would need to make several major modifications to it if you wanted to fly it unmanned, which were considered to be too expensive (and, in some cases, dangerous) to build in.

A while back, I speculated about using the Shuttles as unmanned delivery trucks for the ISS after 2010...basically flying them till they burn up or blow up someday. Other than upgrading the autopilot to function more like an RPV, what other mods would be needed, oDoug?

[dvandorn]

A while back, I speculated about using the Shuttles as unmanned delivery trucks for the ISS after 2010...basically flying them till they burn up or blow up someday. Other than upgrading the autopilot to function more like an RPV, what other mods would be needed, oDoug?

In addition to Jim's excellent answer, there is one major item that the Shuttle designers made manually controlled, for *very* good reason. The landing gear.

You see, when the gear are deployed, they cannot be retracted without external help. Since landing at 300+kph without one or more of the gear down would destroy the vehicle, the gear are designed with a lot of "positive deployment" features. The short version is, once they are down, they are staying down until external hydraulics are attached to retract them.

So, if the gear were ever to deploy in orbit, you would never get that orbiter back. You can't make a successful entry with the gear doors open. That's why the gear are protected with a separate arming switch and a manual circuit breaker. If the gear were capable of being automatically deployed, that would open up te potential for a short circuit or a bad line of code (or just an electrical surge) to cause the destruction of a multi-billion-dollar vehicle.

Yeah, you could always automate the landing gear for unmanned flight. But you'd degrade its capability for re-flight by a small but significant fraction -- and by NASA's rules, you'd not again be able to man the spacecraft in that configuration, since it opens up a few single-point failure modes that would result in loss of crew.

-the other Doug