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RCgothic

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Posts posted by RCgothic

  1. This decision looks bonkers.

    1) Not New Glenn. Ouch, that's embarrassing.

    2) Not Vulcan, which uses BO's engines. Again, ouch.

    3) Atlas V *starts* from about 10x Falcon 9's internal cost to SpaceX, so that's a huge cost handicap before they even start.

    4) Thought ULA were supposed to be phasing Atlas out?

    Better put that larger fairing to use and launch a lot of sats at once. The heaviest Atlas can put up about 25% more mass than F9 in reusable mode but at a still higher price that perhaps counters the benefit of using a heavier variant.

  2. A 2-stage starship fully fuelled could weigh more than a Saturn V on the pad. Imagine a Saturn *starting* from LEO. Starship can do that. Tanker flights are inexpensive.

    And then they could be daisy chained. Stick a third on the back. 3 stages can send a fully fuelled starship over a km/s past earth's escape velocity and still recover both tugs to LEO propulsively.

    Four stages? That's a thousand tons to Trans Jupiter Injection.

     

    If they can sort out trans-shipping of cargo, there's really no limit to the payload a starship can take along (as long as it doesn't all have to land).

     

  3. 1 hour ago, tater said:

    Cislunar tugs have been talked about for many decades. SpaceX might actually be able to do them, IMO. I know they have not talked about it, but it makes a lot of sense.

    Imagine SS with the curved nose gone some number of rings above the dome. The fairing is attached using the same hardware used to to dock 2 SS together at the tail—resulting in a tug that can dock nose to tail with another SS.

    This allows a 2-stage SS in orbit. I'm unsure about the ability of such a tug to aerobrake, but it seems like it should potentially be possible, otherwise it has to re-circularize in LEO after putting the other SS into an eccentric HEO (shy of TLI) propulsively—luckily for an empty vehicle this is surprisingly cheap in props.

    Such a vehicle could give a full SS with 100t cargo 2300 m/s and leave props for 100% propulsive recircularization. Now we have a SS headed for the Moon fully tanked, and it needs to provide only 900m/s for TLI (305t props) itself. That gives us a lunar SS with 895t of props remaining otw to the Moon (I'm using 100t for the dry mass, so if SS is less, then more props or more cargo).

    Assume its a normal SS that can aerobrake or aerocaptuure. If the cargo was propellants, and this was a ballistic trajectory to NRHO, we can in fact deliver 995t to NRHO. Some is needed for the 450 ms burn—less than 15t from NRHO. So we have a tanker at the Moon with980t of propellants. If LSS is 85t, then that's ~9.4km/s dv. ~5.5km/s is needed for the RT to the surface from there. Returning LSS has residuals, so future resupply can sacrifice propellant for cargo, and none the less slowly build up the props in LSS to being filled.

    Ooh! I really like this idea! And it gets even better with a 22m variant fairing Starship-tug filled to the cylindrical extent. ~2400m3 or ~2150t of propellant.

    I'd probably keep some manner of fins and aerobrake back into LEO without landing. It could even go up with all RVacs as the intent is for it to never land.

  4. My opinion on the difference between commercial and govt contacts:

    1) A govt agency has a design. It wants the design built, so it goes out to contractors. The contractors haven't necessarily built this before, so because the govt has responsibility for the design, any problems that crop up are the govt's responsibility. The contract is cost+.

    2) A govt agency has a requirement. Suppliers bid their own designs to meet that requirement. The supplier has responsibility for the design and any obstacles it might face. The contract is fixed cost.

     

  5. Dynetics was deservedly rated third, in part because NASA didn't believe they were capable of delivering on the proposed timescale due to low TRLs and negative mass budget, and that's all moot because  NASA couldn't afford it anyway.

    NASA believe SpaceX are most capable of delivering on the required timescale and at a price NASA can afford. That's all there is to it.

  6. From an outsider view, Dynetics seemed to have a better design than Blue and more achievable than SpaceX. If I were NASA I'd have had a preference for Dynetics all other things being equal.

    But the report rated their technical plan as marginal, and having read the decision summary I agree with it. It's a surprise Dynetics came in third, but on the basis of progress so far, I think NASA were right to rate Blue 2nd and Dynetics 3rd.

  7. This is how the bids were rated at the previous phase:

    Blue Origin: Technical Rating: Acceptable, Management Rating: Very Good (most expensive)

    Dynetics: Technical Rating: Very Good, Management Rating: Very Good

    SpaceX: Technical Rating: Acceptable, Management Rating: Acceptable (cheapest)

     

    From April 2021 selection statement:

    Blue Origin: Technical Rating: Acceptable, Management Rating: Very Good

    Dynetics: Technical Rating: Marginal, Management Rating: Very Good (most expensive)

    SpaceX: Technical Rating: Acceptable, Management Rating: Outstanding (cheapest)

     

    Blue Origin held steady, Dynetics plummeted on the technical side, and SpaceX more than overcame doubts about its management capability.

  8. Basically, Dynetics' design was overweight and had to find mass to lose. But the report also states there were significant risks of mass *increases* still to come which would also need to be countered, and the report did not expect that was feasible.

    Sounds like Dynetics bit off more than they could chew with their concept, even though it would have been a great capability if they'd been able to get it to work.

    This is the sort of thing armchair speculators can't predict. It was a surprise Dynetics was rated this low, but there was no way we could evaluate things like mass budgets or lack of progress on development of the critical MULE refueler.

  9. The report implied that the all up development for Starship is likely to be somewhere in the ballpark of $6Bn to $10Bn for booster, ground systems and starship variants.

    Considering this is the largest, most complicated spacecraft ever on the most powerful booster by a factor of 2, that's not bad going.

    Sure, it's not cheap (a lot cheaper than some others) but less than half is tax dollars and the amount beyond that doesn't really matter. As long as SpaceX deliver a working vehicle the taxpayer had nothing to complain about in this, and as long as SpaceX can afford to service the interest on their private debt it's all good.

  10. Another interesting set of wording in the report is that "SpaceX's plans to self fund and assume financial risk for over half of the development and test activities as an investment in its architecture..."

    That wording is interesting. "More than half". Not "three quarters of" or "the vast majority of".

    SpaceX bid $2.94Bn. On the basis of the above I think it's likely that this indicates total starship development will be less than $10Bn in total.

  11. The report has an interesting section on abort capabilities.

    Basically, excess capacity in all things leads to improved survivability. Multiple redundant engines is a plus. Excess propellant gives greater ability to return to rendezvous orbits. Greater consumables storage gives much greater ability to linger waiting for a rescue.

    This was a significant strength of the lunar starship proposal which stands in stark contrast to the criticisms it gets as a launch vehicle.

  12. Crew-2 progressing.

     

     

    SpaceX's announcement tweet.

     

     

    And of course what we will knew but old-space is extremely slow to acknowledge:

    If you're just trying to copy F9 you're destined for failure. Starship may not work reusably, but there's no serious reason not to think Superheavy won't even so be by far the cheapest ride to space on a per kg basis.

     

  13. Just now, sevenperforce said:

    Looks like four banks of six engines each for a total of 24.

    worse.png

    Wow, I didn't spot the ones above and to the right.

    24 landing engines then. What do we reckon, somewhere in the region of 25kN per engine? That's quite a bit smaller than superdraco.

  14. 7 minutes ago, CatastrophicFailure said:

    Interesting... I’m not seeing any side-firing mini-Raptors... maybe there’s a ring of even-mini-er engines? The mythical hot-gas thrusters, perhaps, spammed around enough to land in lunar grabbity?

     

    In the darker ring above and to the left of the flag and the NASA logo.

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