Depending on the Brigade configuration, the ARG (that's two LHD and one LSD) can lift 25% - 50% of a Brigade. For planning considerations, figure it lifts 33%. I'd be looking at most of the heavy armour and engineering vehicles, 80% of SPH, 40% of IFVs and 20% of CRVs. With applicable trucks and materiel. I can ignore TG Aviation - it fits around the edges. I'm still looking at lifting another 500 - 650 vehicles ranging from M1 chassis to Hawkei along with a hospital, and a few hundred tonnes of ammunition, fuel, food, water and random supplies. I have to plan on the Brigade being self sufficient for at least 8 days, although it's likely to be 14 (that'll allow the vessels to return to Australia, load supplies and return; some of those supplies will be attrition materiel to replace the losses taken). You can assume the second lift is about carriable on a ARG without supplementation - but the ARG may have taken losses.
So across two weeks I need the lift capability of 4x what we have - but only 3 simultaneously. If the answer is a third or fourth LHD, you still can't quite lift the first element. It does guarantee an LHD online at all times so you can put the RCT anywhere you want - but the RCT has to do the job quickly and get out - or be reinforced. That may be more than adequate for a evac or HADR task of course.
#3 and #4 also come with costs. It is really, really rough, but assume for crewing, funding and berthing purposes an LHD = a FFG (it's probably closer to 1.5 FFG for crewing and funding.....but lets stick to 1:1). So you are giving up Hunter #8 and Hunter #9. But in a situation where you are putting a Brigade ashore, an 8th and 9th Hunter is likely to be super useful (if only as attrition stock). So - are you willing to risk that? The fact is that the RAN is 105% allocated for the next 10 - 15 years too, so throwing a new ship in means taking one out.
Really, I think it comes down to civilian shipping - just like the Falklands and almost every WW2 landing. We need something that can surge, provide the lift we need (and that lift may be a constant resupply to a friendly port a'la supporting forces in Korea) but not cost us the price of a FFG. There are enough types of ships out there - it's just up to JLC to charter the correct ones!
Sea lift is about to be our Achilles heel. A recent US exercise (
The US military ran the largest stress test of its sealift fleet in years. It’s in big trouble.) showed significant flaws - so assuming the US will lift our stuff has gone from not likely to not plausible...