The minister, who described himself as a passionate believer in the UK, said: "As we get closer to the referendum, the level of evidence the Scottish people will be demanding of those who are proposing a break-up will get higher; the bar will be set higher.
"I don't see any sense that the Nationalists are rising to that demand for evidence; all we are seeing is more rhetoric."
The Defence Secretary denied the pro-UK camp was being too negative, saying it is right to focus on the "extraordinary risks that the Scots would be taking if they decided to vote for separatism".
The Surrey MP also insists that tomorrow, on his third visit to Scotland this year to make a speech and meet military veterans in Glasgow, he will be accentuating the positive case for the Union, which he describes as an extraordinarily successful story.
"A history that has delivered us…one of the most successful economies. But also our culture, our language, our values have been projected around the world through various means over centuries. We've been hugely successful. We punch way above our weight as a unified nation in a world where, frankly, it's getting harder and harder to do that with the emergence of new centres of power and economic influence."
He declared if "it ain't broke, don't fix it" and, far from being broken, the Union was going from strength to strength. Asked if a No vote would be a door to further devolution, he replied: "Logically, it would. I can't see what the next stage of devolution would mean other than more responsibility, more accountability for Holyrood and with it more powers." Asked if that meant more tax powers, he said: "Tax powers would be part of it, I'm sure."
Mr Hammond says he is horrified at the prospect of the golden thread of historic tradition of Britain's armed forces being broken.
"It's a huge part of what the military call the moral component of our fighting force; the regimental traditions, the battle honours, the sense of being part of an entity that has fought together and worked together and achieved so much over so many years.
"The Scots have a disproportionate stake in the success of our armed forces. If you look back over the last 200 years of our history Scottish regiments, Scottish soldiers, Scottish sailors and more recently Scottish airmen have made a huge contribution and in many parts of Scotland military traditions are very strong and very deeply embedded."
He derides the SNP Government's defence budget for an independent Scotland, suggesting it is not £2.5bn as proposed but nearer £2bn. Mr Hammond denied claims the UK Government has short-changed Scotland, which the Nationalists say provides £3bn to the military but gets back only £2bn spent north of the border.
"That in a sense says it all. Defence is about defending our country, it is not about spending every pound of defence money in some pre-proportioned fashion in support of some other agenda ... in point of fact, we will have, by the time we have finished the Army rebasing plan, a higher proportion of our military based in Scotland than we did in 2012 when the announcement was made."
Mr Hammond says he challenged the SNP Government over its defence proposals 13 months ago and is still waiting a rebuttal.
"It's staggering beyond belief that people in Scotland are genuinely being asked to make a huge decision of this magnitude for their future and despite the questions being very clearly set out and presented, there has been absolutely no attempt by the Nationalists to answer them."