sevenperforce

For reference: current NTR designs push about 925 s Isp and 110 kN. You wouldn't want more than about an hour of burntime, so for a TMI of about 3.8 km/s for a nominal Mars mission, you'd want an acceleration of around 1.1 m/s2 or 0.11 gees. Your m0 will be around 100 tonnes and your payload will be on the order of 55-60 tonnes. So you'd need SLS Block 1B or BFR just to get it into orbit. There's no need for that kind of payload, short of a manned Mars mission.

Dammit, I meant out of the Earth SOI. Wow. This is what I get for posting before my caffeine buzz hits.

Nuclear thermal rockets are good for launching really big payloads really fast. But not so good if those payloads are squishy humans, because then you need radiation shields, and that grows your dry mass almost beyond their efficiency utility. So you only need nuclear thermal rockets if you are launching big non-human payloads. For example, if you were sending an all-expendable manned mission to Mars and needed to send supply/cargo out first. However, unless you have a REALLY big rocket, then your big cargo and big NTR and big hydrogen tanks will be too much to send up as a monolith, so you need to do it piecemeal on a slightly smaller really big rocket. But if you're doing it piecemeal, then you can just do orbital propellant transfer with a reusable rocket and you don't need to bother with nukes at all.

Getting a tweet about BFR construction from a non-SpaceX source is surreal...like, "finally this is no longer just Musk head-canon". The launch yesterday would have been at 6:30 EST, the launch on Wednesday is planned for 6:50 EST, which will phase the argument of periapsis by only 5.0 degrees. The moon orbits through 24.4 degrees in the span of two days. So that's not enough. Instead, TESS is being tossed into an elliptical high earth orbit with its apogee about 60% of the way to the moon. It will use its own thrusters to precisely adjust the size (and thus the period) of its orbit, over multiple orbits, so that the moon will catch up to it at exactly the right time. A day or two difference in launch timing is easy enough to compensate for; it will just enlarge its orbit slightly less than it otherwise would have, so it completes its several orbits at the perfect moment. Those adjustments are too fine to be performed by the MVac. No, the TESS upper stage is going hyperbolic. It's so close to escape anyway; easier to just toss it out of the solar system Earth-moon system than to try a retroburn.

Good call.

I...hope so? Well, let's be realistic then. SLS has slipped before and will slip again. SpaceX may fly Dragon 2 this year, definitely by next year. BFS will be conducting flight tests by the end of next year or first quarter of 2020 at the latest. BFR will be flying before SLS flies people. Whether they are flying BLEO remains to be seen.

GNC on F9, definitely. SpaceX would say it was payload otherwise. Like it or not, SpaceX is definitely going to need to get a wee bit better at some of this stuff before it can support the kind of launch cadence it needs. "If your payload absolutely, positively has to go to space today...." And what's more, I just flew this entire mission in KSP (and realized that KSP's engine does NOT like semisynchronous halo orbits).

nothing new

I would definitely expect a higher vacuum Isp. I know the BE-3 has very deep throttle ability, which means its chamber pressure needs to be quite high (to inhibit flow separation), which probably means a slightly greater combustion tap-off (to run the turbopump) than would be necessary for a smaller throttle range. But 406 has got to be way, way too low. Too low, even, for the BE-3 vacuum Isp without the bigger nozzle.

http://www.b14643.de/Spacerockets_2/United_States_1/B.O._New-Glenn/Propulsion/engines.htm There's the BE-3U. I was looking for those work lights too. Then I realized there is someone standing right behind it:

Air drag is almost always determined by wind tunnel testing; it's far too complex to be done reliably any other way.

So Mach 0.55 or so.

Without trying to dash your hopes and dreams.... If you're applying to work for a US corp, your English needs to be better. A lot better. Find a tutor or ESL class or something. Also, ITAR.

Added the launch and mission!

When is Centaur burn 3?

Wouldn't need to last a day; it's just one burn out of LEO. Block 4 Falcon 9 would have no trouble sending 370 kg far beyond Mars, even with ASDS recovery. The destination orbit is about phase timing for a precise lunar slingshot and nothing else.

Atlas V 551 is ready to loft its payload!

AFSPC-11 Not a lot is known about this mission, and there are a LOT of components, so...I did the best I could. Love how well the Atlas V 551 comes together, though.

Yes, I have F9 Block 4 being able to send over 4 tonnes to TLI with comfortable margins. The reason it is only going part of the way to TLI is that it has a very complex set of maneuvers in order to get it into a line-up for a lunar flyby, which must be executed precisely so that it ends up in the desired super-stable orbit. Likely not a MRS; they may even play around with delayed BLEO restarts on the US. If the F9 boosts TESS too high, its orbits will be too long and it will miss its preferred encounter.

I thought, oh, good lord, She had them long tanned legs Couldn’t help myself So I walked up and said.....

I have. Although a leak began in the hydrogen tank at T+64.66, it was the failure of the aft right strut at T+72.284 which led to the immediate breakup of the orbiter. The ET did not experience structural failure until T+73.124. Had the SRBs included a TTS option, then automated systems would have been in place to trigger TTS. Loss of right SRB chamber pressure at T+59 could have been one of the triggers, five to six seconds before the ET began leaking and a full thirteen seconds before the eventual structural failure of the aft right strut. Had a TTS been commanded prior to (or even just after) the formation of a leak in the ET, without jettisoning the SRBs, it is not inconceivable that the stack could have maintained aerodynamic stability (it was relatively draggy in the back and had the heavy oxygen tank up front) long enough to perform a controlled pitch-forward using the SSMEs and then jettison tank and SRBs together, allowing the orbiter to enter the airstream prograde, rather than uncontrolled and at a high AoA with one wing sheared off. Obviously no such contingency was planned, as they had no safe way of shutting down the SRBs in the event of an SRB problem.

By then it was probably too late, the plume had been eating away at the skin of the ET since right after SRB ignition. IIRC, plume impingement was primarily on the lower SRB holding strut. That strut eventually melted away enough that it failed, and the still-firing SRB then rotated around its remaining two attachment point, striking the ET and rupturing it. As the stack started to spin out of control, the SRB ripped free and impacted the right wing of the orbiter and the whole stack ripped itself apart with the two SRBs flying off merrily until FTS trigger. If the SRBs had a thrust termination option, then they would have evaluated automatic shutdown protocols. The stack was already experiencing thrust shortfall, pressure fluctuations, and pointing problems before T+70; automatically-commanded shutdown of the SRBs based on telemetry would have at least been an evaluated possibility. And the question of whether other possible failures could have also been prevented by TTS is still open.

...because there is no SRB TTS. I do not have quite the engineering and analysis chops to say that zeroing the thrust on the Challenger SRBs at T+70 would have definitely saved the lives of the crew, but I think we can be pretty darn certain that it could not possibly have been worse than STS-51-L.

NASA didn't seem to have a problem doing so. Thrust termination (for the Shuttle) was dropped because a propulsion system powerful enough to get the orbiter away from the stack was too heavy, not because of plume impingement. If the SRBs had been equipped with TTS, then there would have been a chance that they could have cut Challenger's SRBs off, jettisoned them, dropped the tank, and prayed. Probably still would have broken apart due to aerodynamics, but there would have been a chance. And there were definitely other parts of the ascent envelope prior to booster cutoff that would have allowed benign abort without an active LES.

Eh, the ITS was "overwhelmingly large". On the positive side, we now have a name for it. The Space-X-tenze!